Uses and Potential Benefits of Iron Supplements
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What Has Changed in Iron Supplementation Over the Past Ten Years?
Iron deficiency is the world's most common nutritional problem, and its treatment seems simple: taking an iron pill. However, knowledge about how to take it has changed fundamentally over the past ten years. We now know that taking more iron does not mean absorbing more iron. After a dose, the body closes the door for approximately 24 hours. This article discusses both the correct diagnosis and treatment of iron deficiency and a critical question often overlooked in this situation: why did iron become depleted?
The three main messages of this article:
- The dosing strategy has changed. The traditional approach of “2-3 times a day, a total of 150-200 mg” is being replaced by a single daily dose of 50-100 mg or a single dose on alternate days . The reason is the hormone called hepcidin .
- The vitamin C recommendation is not supported by evidence. The advice to “take your iron pill with orange juice,” tested in a randomized study involving 440 patients, made no difference.
- Iron deficiency anemia in adults is a finding, not a diagnosis. Among investigated cases in men and postmenopausal women, approximately %8-10 have cancer . Giving iron alone without looking for the cause is a serious mistake.
What Does Iron Do in the Body?
Iron's best-known role is to form part of the structure of hemoglobin , the protein in red blood cells that transports oxygen from the lungs to tissues. However, its role is not limited to this:
| Structure | Function | What happens in deficiency |
|---|---|---|
| Hemoglobin | Oxygen transport in the blood | Weakness, shortness of breath, palpitations, pallor |
| Myoglobin | Oxygen storage in muscles | Reduced muscle strength and endurance |
| Cytochrome enzymes | Energy (ATP) production in cells | Fatigue — even before anemia develops |
| Ribonucleotide reductase | DNA synthesis | Slower cell division |
| Brain enzymes | Dopamine and myelin production | Distractibility, restless legs syndrome; developmental problems in infants |
| Ferritin | Iron storage | Stores are depleted first; anemia appears last |
Knowing the sequence is important. Iron deficiency does not occur in a single step; it progresses in three stages: first, stores are depleted (ferritin falls while hemoglobin remains normal), then iron deficiency develops (less iron reaches the tissues), and finally anemia appears. Therefore, saying “my hemoglobin is normal, so my iron is fine” is incorrect. Fatigue can begin before anemia develops and can be treated.
Two types of iron in food
| Heme iron | Non-heme iron | |
|---|---|---|
| Source | Red meat, liver, chicken, fish | Lentils, chickpeas, spinach, raisins, molasses, grains |
| Absorption | High — minimally affected by other foods | Low — significantly affected by tea, coffee, calcium and phytates |
This difference is why the iron requirements of vegetarians and vegans are considered 1,8 times higher. The recommended daily intake is, for adult men, 8 mg; for women aged 19-50, 18 mg; during pregnancy, 27 mg. The upper limit of intake without supplements is 45 mgper day.
Symptoms and Diagnosis
Symptoms
| Common symptoms | Less well-known but typical symptoms |
|---|---|
| Persistent fatigue and weakness | Pica — the urge to eat ice, soil or clay (ice eating is particularly characteristic) |
| Shortness of breath during exertion | Restless legs syndrome — the need to move the legs at night |
| Pallor of the skin, palms and inner eyelids | Spoon-shaped nails (koilonychia) — inwardly concave nails |
| Dizziness, vision darkening when standing up | Cracks at the corners of the mouth, burning and smoothing of the tongue |
| Palpitations | Hair loss |
| Cold hands and feet | Difficulty paying attention and concentrating |
Defining Anemia: Which Hemoglobin Level Is Considered Low?
The World Health Organization updated its hemoglobin thresholds in 2024. Adult thresholds remained unchanged; the only change was for infants aged 6-23 months (110 → 105 g/L).
| Group | Anemia threshold (g/dL) |
|---|---|
| Adult men | < 13,0 |
| Nonpregnant adult women | < 12,0 |
| Pregnancy — 1st trimester | < 11,0 |
| Pregnancy — 2nd trimester | < 10,5 |
| Pregnancy — 3rd trimester | < 11,0 |
| Infants aged 6-23 months | < 10,5 (updated in 2024) |
| Ages 2-5 | < 11,0 |
| Ages 5-11 | < 11,5 |
| Ages 12-14 | < 12,0 |
We are correcting an error in the article this one replaces. The old text stated that “iron supplementation is inevitable in people whose hemoglobin level is below 10 g/dL.” This threshold is incorrect and misleading: the anemia threshold is 12 for women and 13 g/dL for men. More importantly, the decision to give iron treatment is based on iron stores, not hemoglobin. A person with completely normal hemoglobin may require treatment if ferritin is low and they complain of fatigue.
Which Tests Should Be Ordered?
| Test | What it shows | Threshold |
|---|---|---|
| Complete blood count (Hb, MCV, RDW) | Whether anemia is present and cells are small | Low MCV = microcytic anemia |
| Ferritin | Iron stores — the single most valuable test | <15 µg/L: definitive diagnosis (specificity 0,99) <30 µg/L: low stores <45 µg/L: threshold increasing sensitivity |
| Transferrin saturation (TSAT) | Ratio of circulating iron to its carrier | < %20 |
| Serum iron and TIBC | Supportive | Low iron, high TIBC |
| CRP | Whether inflammation is present — essential for interpreting ferritin | If high, the ferritin threshold is raised |
Ferritin's major pitfall: Ferritin is also an acute-phase protein. In the presence of infection, inflammatory disease, liver disease, cancer or obesity, ferritin may be normal or even high despite iron deficiency. In this situation:
- The ferritin threshold is raised to 100 µg/L and must be assessed along with TSAT as part of the same evaluation.
- In chronic kidney disease (KDIGO 2026): in patients not on dialysis, ferritin <100, or a level between 100-299 with TSAT <%25, is considered iron deficiency.
- In heart failure: ferritin <100 µg/L, or when between 100-299, TSAT <%20.
The Critical Question: Why Did Iron Become Depleted?
This is the most important section of the article and is often overlooked. Iron deficiency is a finding, not a diagnosis. There must be a reason for an adult's iron stores to become depleted.
| Mechanism | Causes |
|---|---|
| Blood loss | Heavy menstrual bleeding; occult gastrointestinal bleeding (ulcers, polyps, cancer, angiodysplasia, hemorrhoids); frequent blood donation; urinary tract bleeding |
| Malabsorption | Celiac disease (%3-5 of cases), Helicobacter pylori infection, autoimmune atrophic gastritis, stomach surgery/bariatric surgery, inflammatory bowel disease, prolonged use of acid-suppressing medication |
| Increased requirements | Pregnancy, breastfeeding, growth, intensive sports |
| Insufficient intake | Unbalanced diet, not eating meat |
Iron deficiency anemia in adults is a warning sign for cancer.
According to the British Society of Gastroenterology's 2021 guideline, among investigated cases of iron deficiency anemia, approximately %8-10 have cancer detected. Approximately one-third of men and postmenopausal womenhave an underlying condition, most often in the gastrointestinal tract.
According to the British Society of Gastroenterology's 2021 guideline, among investigated cases of iron deficiency anemia, approximately %8-10 have cancer detected. Approximately one-third of men and postmenopausal womenhave an underlying condition, most often in the gastrointestinal tract.
- In men and postmenopausal women with newly diagnosed iron deficiency anemia, both upper and lower gastrointestinal endoscopy (gastroscopy + colonoscopy) are the first-line investigations. CT colonography is an option if colonoscopy is unsuitable.
- In premenopausal women, routine endoscopy is not required; however, investigation is needed if warning symptoms are present, anemia is too severe or recurrent to be explained by menstruation, or there is a family history of gastrointestinal cancer.
- Celiac disease should be screened for using a blood test or a biopsy obtained during endoscopy.
- Urinalysis should rule out bleeding originating in the kidneys or urinary tract.
The Dosing Revolution: Why Could “Less” Be Better?
The molecule guarding the gate of iron absorption is the liver-produced hormone hepcidin . Hepcidin closes the gate on the surface of intestinal cells called ferroportin and prevents absorbed iron from entering the blood.
The critical observation: A single iron dose of 60 mg or more raises hepcidin levels and this elevation lasts approximately 24 hours but returns to normal at 48 hours is when levels return to normal. Thus, absorption of the second pill to be taken in the evening is something the morning iron pill itself blocks.
The Evidence
| Study | What was done | Result |
|---|---|---|
| Moretti, Blood 2015 | In 54 young women with depleted iron stores, absorption of 40-240 mg doses was measured using labeled iron isotopes | After a dose of 60 mg or more, hepcidin was elevated at 24 hours and absorption fell by %35-45. Increasing the dose 6-fold (40→240 mg) increased the absorbed iron only 3-fold . Giving two doses a day rather than a single dose provided no significant additional iron. |
| Stoffel, Lancet Haematol 2017 | 40 women with depleted iron stores; 60 mg daily vs alternate days | Absorption rate %21,8 versus %16,3 — approximately %34 higher |
| Stoffel, Haematologica 2020 | Iron deficiency anemia in 19 women; consecutive vs alternate days | Absorption on the second consecutive day was %40-50 lower. “The total iron absorbed from a single alternate-day 200 mg dose, compared with 100 mg given on consecutive days, was approximately twice as much.” |
Iron absorption rate — Stoffel 2020, 100 mg ferrous sulfate
Percentage of iron absorbed in women with iron deficiency anemia
Day 1 (first dose)
%23,5
Day 2 (second consecutive dose)
%17,0
Dose given on alternate days
%25,0
While absorption falls markedly on the second consecutive day, after a one-day break absorption returns to the level of the first day. The same pattern was seen with 200 mg doses (%17,3 / %11,9 / %16,8).
So What Is Recommended Today?
The British Society of Gastroenterology's 2021 guideline uses the clearest wording: one tablet daily is the starting regimen; 50-100 mg of elemental iron daily is a reasonable balance; if side effects occur, one tablet on alternate days is used instead.
But let us be honest: this issue is not completely settled. The physiology of absorption (hepcidin and absorption percentages) has been demonstrated robustly and reproducibly. By contrast, alternate-day use has not been proven to raise hemoglobin faster. Combining 11 randomized trials and 1.014 participants, a 2025 meta-analysis found a hemoglobin difference of 0,28 g/dL that favored daily use but was not statistically significant (p=0,06); there was no difference in ferritin either, and the evidence level was rated “very low.” Randomized studies published in 2025 also contradict one another.
The most honest defensible statement today is: alternate-day use is at least as effective as daily use, is significantly better tolerated and allows more iron to be absorbed per dose. There is insufficient evidence to say it “produces faster recovery.” Stopping medication because of side effects is the slowest treatment method — therefore, tolerability is important in its own right.
The most honest defensible statement today is: alternate-day use is at least as effective as daily use, is significantly better tolerated and allows more iron to be absorbed per dose. There is insufficient evidence to say it “produces faster recovery.” Stopping medication because of side effects is the slowest treatment method — therefore, tolerability is important in its own right.
The situation in Türkiye: The Turkish Society of Hematology's current Erythrocyte Guideline, dated August 2025, still recommends 180 mg of elemental iron daily in adults (a range of 100-200 mg), but also notes that alternate-day use reduces the frequency of side effects . Thus, our national guideline has not yet fully adopted the low-dose/alternate-day model. Make your dosing decision together with your physician.
The Vitamin C Myth
The advice to “take your iron pill with orange juice” has been repeated for decades. Its rationale is correct: vitamin C really does increase iron absorption in single-meal experiments. However, this does not translate into a faster rise in hemoglobin.
What changes when vitamin C is added? (JAMA Network Open 2020, n=440)
Hemoglobin increase in adults with iron deficiency anemia
Week 2 — iron + vitamin C
+2,00
Week 2 — iron alone
+1,84
Week 8 — iron + vitamin C
+4,20
Week 8 — iron alone
+4,07
Hemoglobin increase in g/dL. The difference at week 2 was 0,16, and at week 8 it was 0,13 g/dL — in other words, clinically insignificant. There was no difference in ferritin increase either (p=0,21). A 2023 meta-analysis combining seven studies reached the same conclusion.
Practical conclusion: Taking vitamin C is not harmful, but it is not necessary either. If you want to take it with orange juice, you can; you lose nothing if you do not. What really makes a difference is the dose size and timing.
What Really Impairs Absorption
| Factor | Effect |
|---|---|
| Black tea | Reduces non-heme iron absorption in a bread-containing meal by %79-94 — the strongest inhibitor |
| Peppermint tea, cocoa, chamomile tea | Reduces it by %47-84 |
| Food (in general) | Reduces bioavailability by up to %75 in total |
| Milk and dairy products (calcium) | Avoidance is recommended; however, the effect is not as strong as commonly believed — calcium doses below 800 mg have been shown not to suppress absorption |
| Antacids, acid suppressants | Acid is needed to dissolve iron; absorption decreases |
Thus, what should primarily be avoided is tea. Taking an iron pill with tea, or drinking tea immediately afterward, is the most common way treatment is undermined.
How Is It Taken? Practical Rules
- On an empty stomach is how it should be taken — preferably in the morning, approximately one hour before breakfast. Taking it with food reduces absorption by up to %75.
- If it causes nausea, with a small snack it may be taken. This reduces absorption, but is better than not taking it at all.
- Keep it at least 1-2 hours apart from tea, coffee and dairy products . This single rule significantly affects treatment success.
- A single dose is sufficient. Taking it two or three times a day does not increase absorbed iron.
- If side effects occur, rather than dividing the dose, discuss switching to alternate days with your physician.
- Thyroid medicines (levothyroxine), certain antibiotics (tetracyclines, quinolones), levodopa, bisphosphonates and antacids should be separated from iron by at least 2-4 hours between doses.
- Drink plenty of water and maintain a high-fiber diet — constipation is the most common side effect.
- Black stools are normal and harmless. However, it can conceal a true gastrointestinal bleed (melena) by masking it; consult a physician if abdominal pain, weakness or dizziness also occur.
- Liquid forms may temporarily stain the teeth; drinking through a straw and then rinsing the mouth prevents this.
- Keep out of reach of children — this is the article's most vital warning (see below).
When Do We Know It Is Working?
| Time | Expected response |
|---|---|
| 2-4 weeks | Hemoglobin increase of at least 1 g/dL is expected. This shows that the diagnosis is correct and treatment is working. |
| If there is no increase after 2 weeks | This signals treatment failure — switching to intravenous iron is considered |
| 2-4 months | Hemoglobin returns completely to normal |
| For a further 3 months after hemoglobin normalizes | Treatment continues to replenish stores. This is the most frequently overlooked step: stopping medication because hemoglobin has improved means returning to the same point within a few months. |
If treatment produces no response, consider: not taking medication regularly (the most common cause), taking it with tea, ongoing bleeding, celiac disease, H. pylori infection, autoimmune atrophic gastritis, a history of stomach surgery, or an incorrect initial diagnosis (thalassemia trait, anemia of chronic disease). In this situation, rather than saying “let's increase the dose,” ask “why is it not being absorbed?”
Intravenous Iron Treatment
When oral iron is inadequate, iron is given intravenously. This option was entirely absent from our previous article, yet today it has become the first choice for many patients.
When Should Intravenous Iron Be Used?
- Inability to tolerate oral iron or no response after 2 weeks
- Malabsorption: celiac disease, after bariatric surgery, atrophic gastritis
- Ongoing bleeding — if losses exceed the amount that can be absorbed
- Inflammatory bowel disease (oral iron may exacerbate the disease)
- Chronic kidney disease, particularly in dialysis patients
- Chemotherapy-related anemia
- Heart failure together with iron deficiency
- During pregnancy in the 2nd and 3rd trimesters, if considered necessary
- Need for rapid correction before surgery
| Product | Active ingredient | In Türkiye |
|---|---|---|
| Venofer, Ferint, Fericose, Ferroven | Iron sucrose | Available |
| Ferinject, Inferject | Ferric carboxymaltose | Available |
| Ferrum Hausmann ampoules, Ferimax, Santafer | Iron polymaltose (intramuscular) | Available |
| Monofer (ferric derisomaltose), Feraheme (ferumoxytol) | — | In Turkish drug registries not found |
Two important safety issues with intravenous iron:
1. Allergic reaction. Serious reactions are rare. In 2013, the European Medicines Agency introduced the following requirement: a test dose is no longer recommended — instead, caution is required with every dose. Administration should take place in a setting with resuscitation facilities, and the patient should be observed for at least 30 minutes after every injection as a safety measure.
An often confused condition is the Fishbane reaction: a transient reaction seen in approximately one in 100 patients , involving chest and back tightness, pain in the trunk muscles and facial flushing — but without low blood pressure, wheezing or airway edema . Management involves stopping the infusion, observing for 15 minutes and restarting at a slow rate if the condition is stable. Antihistamines (diphenhydramine) should not be given for this reaction — they can worsen the condition and cause low blood pressure.
2. Low phosphorus — little known but important. JAMApublished two randomized studies in 2020 comparing two products and finding a striking difference: low blood phosphorus occurred with ferric carboxymaltose at a rate of %73-75, but with ferric derisomaltose at only %8 . The hemoglobin response to the two products was equal. The reason is that carboxymaltose markedly increases the hormone FGF23. Repeated or high-dose administration requires phosphorus monitoring ; prolonged low levels can cause bone pain and fractures.
1. Allergic reaction. Serious reactions are rare. In 2013, the European Medicines Agency introduced the following requirement: a test dose is no longer recommended — instead, caution is required with every dose. Administration should take place in a setting with resuscitation facilities, and the patient should be observed for at least 30 minutes after every injection as a safety measure.
An often confused condition is the Fishbane reaction: a transient reaction seen in approximately one in 100 patients , involving chest and back tightness, pain in the trunk muscles and facial flushing — but without low blood pressure, wheezing or airway edema . Management involves stopping the infusion, observing for 15 minutes and restarting at a slow rate if the condition is stable. Antihistamines (diphenhydramine) should not be given for this reaction — they can worsen the condition and cause low blood pressure.
2. Low phosphorus — little known but important. JAMApublished two randomized studies in 2020 comparing two products and finding a striking difference: low blood phosphorus occurred with ferric carboxymaltose at a rate of %73-75, but with ferric derisomaltose at only %8 . The hemoglobin response to the two products was equal. The reason is that carboxymaltose markedly increases the hormone FGF23. Repeated or high-dose administration requires phosphorus monitoring ; prolonged low levels can cause bone pain and fractures.
Iron in Patients with Cancer
Approximately %39 of cancer patients are anemic at diagnosis; this rate rises during the 5th cycle of chemotherapy to %47 . Very high rates have been reported, such as %81 in gynecological cancers and %77 in lung cancer.
There are two different forms of iron deficiency in cancer patients:
| Type | Definition (NCCN 2025) | Meaning |
|---|---|---|
| Absolute iron deficiency | Ferritin <30 ng/mL and TSAT <%20 | Stores are genuinely empty |
| Functional iron deficiency | Ferritin 30-500 ng/mL and TSAT <%50 | Iron in stores is present but cannot be used because of inflammation (hepcidin) |
In functional iron deficiency, oral iron does not work — because the problem is utilization, not intake. The NCCN guideline states this explicitly: “Intravenous iron has superior efficacy and should be preferred. Although oral iron is more widely used, it is less effective.”
“Does Iron Feed the Tumor?” — An Honest Answer. This is a question patients frequently ask and a concern echoed online. Here is what is known:
- Epidemiological studies have shown dietary heme iron (meaning red meat) to have a small association with colorectal cancer: for a daily increase of 1 mg, the risk ratio for colon cancer is 1,12. There is no significant association with breast or lung cancer.
- Interestingly, three-quarters of studies measuring body iron stores using ferritin found the association in the opposite direction, meaning higher ferritin was associated with a lower risk of colorectal cancer.
- These data concern diet, not iron supplementation for treatment. This distinction is critical.
- In a review of 21 studies examining intravenous iron use in gastrointestinal cancers, no adverse signal concerning tumor progression or survival was found; however, the data are limited and inconclusive.
Iron before surgery: The study examining a single dose of intravenous iron before major abdominal surgery, PREVENTT (487 patients, Lancet 2020), failed to meet its primary endpoint: the rate of blood transfusion or death at 6 months was %29 versus %28 (p=0,84). The only positive signal was a reduction in hospital readmission due to complications (%13 versus %22). There has been criticism that a substantial proportion of enrolled patients may not actually have had iron deficiency.
Products Available in Türkiye and Prices
| Product | Active ingredient | Price |
|---|---|---|
| Oral products | ||
| Ferro Sanol Duodenal 100 mg, 20 capsules | Ferrous glycine sulfate | 229,98 TL |
| Ferro Sanol B syrup, 150 mL | Ferrous glycine sulfate + B vitamins | 152,62 TL |
| Ferrum Hausman Fort 100 mg, 30 coated tablets | Iron polymaltose + folic acid | 229,13 TL |
| Ferrum Hausmann drops, 30 mL | Iron polymaltose 50 mg/mL | 152,63 TL |
| Maltofer oral solution, 20 vials | Iron polymaltose | 272,25 TL |
| Vegaferon Fort | Iron polymaltose + folic acid | 228,96 TL |
| Intravenous / intramuscular | ||
| Inferject 500 mg/10 mL, 1 vial | Ferric carboxymaltose | 6.683,72 TL (public price 2.807,16 TL) |
| Venofer 100 mg/5 mL, 5 ampoules | Iron sucrose | 1.168,01 TL |
| Ferint 100 mg/5 mL, 5 ampoules | Iron sucrose | 1.079,11 TL |
| Ferrum Hausmann 100 mg, 5 ampoules (intramuscular) | Iron polymaltose | 139,96 TL |
Prices are from 2026 lists (oral products: 31 August 2026; intravenous products: 1 April 2026). All iron products require a prescription in Türkiye.
SGK Reimbursement Requirements for Intravenous Iron: Ferric carboxymaltose and iron sucrose with a specialist physician's report are reimbursed. Conditions for the report include gastrointestinal malabsorption, chronic inflammatory bowel disease, active gastrointestinal bleeding, being a hemodialysis patient, heart failure together with iron deficiency, and pregnancy situations considered necessary. Without a report, the out-of-pocket cost of intravenous iron is high — this should be discussed in advance when planning treatment.
Are “New-Generation” Iron Forms Really Better? Forms such as iron polymaltose, sucrosomial (liposomal) iron and iron bisglycinate are marketed as “iron that does not irritate the stomach.” The conclusion of a comprehensive 2024 review is measured: these forms have not demonstrated superiority over conventional iron salts and are significantly more expensive. The bioavailability of iron polymaltose is lower than that of iron salts; in a pediatric study, ferrous sulfate produced a greater increase in hemoglobin over 12 weeks. Sucrosomial iron is very well tolerated, but does not raise ferritin sufficiently while increasing hemoglobin — in other words, it is poor at replenishing stores. Ferrous sulfate, used at a low dose or on alternate days, remains the practical first choice. Furthermore, many iron products sold as “food supplements” are not medicines; their ingredients and elemental iron amounts are not monitored to pharmaceutical standards.
Safety: The Cost of Unnecessary Use
Iron Poisoning in Children — This Article's Most Vital Warning.
Iron tablets are colorful and resemble candy; adult-dose products kept at home can be fatal to young children.
Iron tablets are colorful and resemble candy; adult-dose products kept at home can be fatal to young children.
- 20 mg/kg is the level above which elemental iron ingestion damages the stomach and intestinal mucosa.
- 60 mg/kg or more can cause organ failure and death.
- In the United States, between 1983-2000, at least 43 children died from iron supplement poisoning.
- Its most dangerous feature is the 6-24-hour symptom-free period after ingestion: the child appears well during this time, after which shock and liver failure develop.
A correction regarding hemochromatosis. Many sources, including our previous article, say that “indiscriminate iron use causes hemochromatosis.” This statement is incorrect. Hereditary hemochromatosis is a genetic disease caused by a mutation in the HFE gene; it is not acquiredby taking iron pills. Furthermore, thanks to the hepcidin mechanism, absorption of excess iron in a person with normal iron balance is already automatically suppressed.
The real risk is more ordinary: taking iron for months without monitoring in someone whose deficiency has not been documented. In this situation, the medicine causes unnecessary side effects, delays investigation of the actual cause (such as a source of bleeding) and may lead to an unnecessary long-term increase in ferritin. The correct message is: do not take iron without blood tests, and if you are taking it, have follow-up monitoring.
The real risk is more ordinary: taking iron for months without monitoring in someone whose deficiency has not been documented. In this situation, the medicine causes unnecessary side effects, delays investigation of the actual cause (such as a source of bleeding) and may lead to an unnecessary long-term increase in ferritin. The correct message is: do not take iron without blood tests, and if you are taking it, have follow-up monitoring.
| Side effect | Frequency |
|---|---|
| Constipation | %12 |
| Nausea | %11 |
| Diarrhea | %8 |
| Black stools | Expected and harmless |
| Metallic taste in the mouth | Common |
In an analysis including 43 randomized studies and 6.831 participants, ferrous sulfate increased the risk of gastrointestinal side effects compared with placebo by 2,3-foldand compared with intravenous iron by 3,1-fold . An interesting finding: no significant association was found between side-effect frequency and dose amount — suggesting that the benefit of alternate-day use may relate to the number of exposure days rather than the size of the dose.
Regarding Iron and Infection Risk: In a large study of 24.076 children in Zanzibar (Lancet 2006), the risk of death or hospital admission in groups receiving iron + folic acid was %12 higher and the study was stopped early. However, the context is critical: this was preventive treatment given to all children, regardless of whether they had iron deficiency, in an area with high malaria prevalence. The World Health Organization's 2016 assessment states that no such increase in risk occurs in settings with malaria screening and treatment services. This finding does not apply in countries without malaria or to treatment of documented iron deficiency.
Special Groups
| Group | Approach |
|---|---|
| Pregnant women — practice in Türkiye | The Ministry of Health's Iron Supplementation Program for Pregnant Women: daily 40-60 mg of elemental iron, from the beginning of the 4th month, for 6 months during pregnancy + 3 months postpartum, a total of 9 months. Avoiding preparations containing calcium and magnesium is recommended. |
| Pregnant women — WHO intermittent regimen | If daily use is not tolerated and the prevalence of anemia in pregnant women in the community is below %20: 120 mg iron + 2.800 µg folic acid once a week |
| Infants and children | WHO preventive regimen: 6-23 months 10-12,5 mg/gün, ages 2-5: 30 mg/gün; ages 5-12: 30-60 mg/gün — for 3 months each year. Treatment dose (THD 2025): 3-6 mg/kg/gün, for at least 3 months. |
| Vegetarians and vegans | Iron requirements are considered 1,8 times higher. Consuming it with vitamin C-containing foods and soaking/sprouting legumes increases absorption. |
| Heart failure | Definition of iron deficiency: ferritin <100 µg/L or when between 100-299, TSAT <%20. Intravenous iron studies (FAIR-HF, AFFIRM-AHF, IRONMAN) showed improvements in symptoms and hospitalization but did not demonstrate a survival benefit. |
| Athletes and blood donors | Iron stores may decrease. However, a reliable recommendation regarding the ferritin threshold at which supplementation should begin in these groups does not exist; the decision should be individualized. |
| Iron Deficiency Without Anemia | In nonanemic menstruating women with ferritin <50 µg/L, iron treatment for 12 weeks reduced fatigue scores by %47,7 (placebo %28,8; p=0,02) — while hemoglobin rose by only 0,32 g/dL. Thus, the benefit largely does not relate to blood count values. |
Frequently Asked Questions
- Do I Really Need to Take My Iron Pill on an Empty Stomach?
- Yes, if possible. Food can reduce absorption by up to %75. However, taking it with a light snack rather than stopping because of stomach discomfort is much better. The indispensable rule is to keep it separate from tea and coffee.
- How Many Tablets Should I Take Daily?
- The current approach is one tablet daily. If side effects occur, one tablet on alternate days is considered. Taking it two or three times a day does not increase the amount of iron absorbed — because the first dose blocks absorption of the next. Your physician determines your exact dose.
- How Long Will I Take It?
- After hemoglobin returns to normal, for at least another 3 months — to replenish stores. The total duration is 3-6 months for most patients, sometimes 9-12 months. Stopping early because hemoglobin has improvedis the most common mistake.
- It Causes Constipation. What Should I Do?
- Plenty of water, a high-fiber diet and, if necessary, a stool softener can help. Constipation should not be a reason to stop treatment; discuss switching to alternate-day use or trying another formulation with your physician.
- Does Iron Cause Weight Gain?
- No. Iron has no calories. However, appetite and energy may increase as anemia improves; if weight gain occurs, it is due not to the medicine but to improved general health.
- My Ferritin Is Low but My Hemoglobin Is Normal. Do I Need Treatment?
- You may. Iron deficiency begins before anemia and may cause fatigue. Iron treatment has been shown to significantly reduce fatigue in nonanemic women whose ferritin is below 50 µg/L. The decision is based on your symptoms and ferritin level.
- Should I Take It with Orange Juice?
- It is not essential. In a randomized study involving 440 patients, adding vitamin C for hemoglobin and ferritin recovery made no significant difference. You can take it if you want, but do not regard it as a rule.
- Does Taking Iron Pills Increase Cancer Risk?
- No. What is associated with cancer risk is dietary heme iron (red meat), and even that association is small. There is no evidence that iron supplementation used to treat documented deficiency causes cancer. By contrast, taking iron when there is no deficiency has no benefit.
- Does Intravenous Iron Complete Treatment in One Session?
- With ferric carboxymaltose, in most patients one or two administrations are sufficient; iron sucrose requires more sessions. The total amount needed is calculated according to your weight and hemoglobin level. The maximum dose that can be given in a single administration is 1.000 mg.
- I Have Iron Deficiency. How Much Investigation Is Needed?
- This depends on your age and sex. In men and postmenopausal women gastrointestinal endoscopy (stomach + colon) is the standard approach. In premenopausal women, menstruation may be a sufficient explanation; however, investigation is required if anemia is more severe than expected, recurs or is accompanied by warning symptoms. In addition, celiac disease should be screened for in everyone.
Transparency note. (1) Alternate-day use has not been proven to raise hemoglobin faster; superior absorption has been demonstrated, but clinical superiority has not. This distinction is maintained in the article. (2) Turkish drug prices were obtained from secondary databases ; the official TİTCK list could not be accessed directly, and the current price of Ferinject could not be verified. (3) For products in Türkiye, the amounts of elemental iron per unit could not be verified from summaries of product characteristics; dose calculations should be based on the information inside the package. (4) It could not be verified whether ferric derisomaltose (Monofer) and ferumoxytol are licensed in Türkiye; they could not be found in Turkish drug registries. (5) For restless legs syndrome, the ferritin thresholds used to initiate iron treatment could not be verified from the primary guideline text, so no numerical values are given. (6) The widely cited range of days on which the reticulocyte response begins could not be verified. (7) For intravenous iron products, anaphylaxis rates could not be verified from the primary source and therefore are not given numerically. (8) The contents of the American Academy of Pediatrics' current report on children and infants, published in 2026, could not be accessed. Drug prices change frequently in Türkiye; confirm them with a pharmacy before purchasing.
This article is for informational purposes and does not replace personal medical advice. Iron supplements should be used for deficiency documented by blood tests and on a physician's recommendation. The cause of iron deficiency anemia detected in an adult must be investigated.
References
- Moretti D, et al. Oral iron supplements increase hepcidin and decrease iron absorption from daily or twice-daily doses in iron-depleted young women. Blood 2015;126:1981-9.
- Stoffel NU, et al. Iron absorption from oral iron supplements given on consecutive versus alternate days. Lancet Haematol 2017;4:e524-33.
- Stoffel NU, et al. Iron absorption from supplements is greater with alternate day than with consecutive day dosing in iron-deficient anemic women. Haematologica 2020;105:1232-9.
- Snook J, et al. British Society of Gastroenterology guidelines for the management of iron deficiency anaemia in adults. Gut 2021;70:2030-51.
- Li N, et al. Effect of oral iron supplementation with and without vitamin C on hemoglobin and ferritin recovery in patients with iron deficiency anemia: a randomized clinical trial. JAMA Netw Open 2020;3:e2023644.
- World Health Organization. Guideline on haemoglobin cutoffs to define anaemia in individuals and populations, 2024.
- Turkish Society of Hematology. Erythrocyte Diagnosis and Treatment Guideline, Version 1.4, August 2025.
- Republic of Türkiye Ministry of Health. Circular on Implementation of the Iron Supplementation Program for Pregnant Women, 2007/6.
- Tolkien Z, et al. Ferrous sulfate supplementation causes significant gastrointestinal side-effects in adults: a systematic review and meta-analysis. PLoS One 2015;10:e0117383.
- Wolf M, et al. Effects of iron isomaltoside vs ferric carboxymaltose on hypophosphatemia in iron-deficiency anemia: two randomized clinical trials. JAMA 2020;323:432-43.
- European Medicines Agency. New recommendations to manage risk of allergic reactions with intravenous iron-containing medicines, 28 June 2013.
- NCCN Clinical Practice Guidelines in Oncology: Hematopoietic Growth Factors, v1.2025.
- Aapro M, et al. Management of anaemia and iron deficiency in patients with cancer: ESMO Clinical Practice Guidelines. Ann Oncol 2018;29(Suppl 4):iv271.
- Fonseca-Nunes A, et al. Iron and cancer risk: a systematic review and meta-analysis of the epidemiological evidence. Cancer Epidemiol Biomarkers Prev 2014;23:12-31.
- Richards T, et al. Preoperative intravenous iron to treat anaemia before major abdominal surgery (PREVENTT): a randomised, double-blind, controlled trial. Lancet 2020;396:1353-61.
- Vaucher P, et al. Effect of iron supplementation on fatigue in nonanemic menstruating women with low ferritin. CMAJ 2012;184:1247-54.
- Sazawal S, et al. Effects of routine prophylactic supplementation with iron and folic acid on admission to hospital and mortality in preschool children in a high malaria transmission setting. Lancet 2006;367:133-43.
- Hurrell RF, Reddy M, Cook JD. Inhibition of non-haem iron absorption in man by polyphenolic-containing beverages. Br J Nutr 1999;81:289-95.
- Oral iron supplementation: new formulations, old questions. Haematologica 2024.
- KDIGO 2026 Clinical Practice Guideline for Anemia in CKD.
- National Institutes of Health, Office of Dietary Supplements. Iron — Health Professional Fact Sheet.
Sources
1. Clara Camaschella,M.D.
Iron-Deficiency Anemia.
N Engl J Med 2015
2. Mielgo-Ayuso J, Zourdos MC, Calleja-González J, Urdampilleta A, Ostojic S.
Iron supplementation prevents a decline in iron stores and enhances strength performance in elite female volleyball players during the competitive season.
Appl Physiol Nutr Metab. 2015
3. Brutsaert TD1, Hernandez-Cordero S, Rivera J, Viola T, Hughes G, Haas JD
Iron supplementation improves progressive fatigue resistance during dynamic knee extensor exercise in iron-depleted, nonanemic women.
Am J Clin Nutr. 2003
4. Trotti LM, Bhadriraju S, Becker LA.
Iron for Restless Legs.
Cochrane Database Syst Rev. 2012
5. Ridefelt P, Larsson A, Rehman JU, Axelsson J.
Influences of sleep and the circadian rhythm on iron-status indices.
Clin Biochem. 2010 Nov
Iron-Deficiency Anemia.
N Engl J Med 2015
2. Mielgo-Ayuso J, Zourdos MC, Calleja-González J, Urdampilleta A, Ostojic S.
Iron supplementation prevents a decline in iron stores and enhances strength performance in elite female volleyball players during the competitive season.
Appl Physiol Nutr Metab. 2015
3. Brutsaert TD1, Hernandez-Cordero S, Rivera J, Viola T, Hughes G, Haas JD
Iron supplementation improves progressive fatigue resistance during dynamic knee extensor exercise in iron-depleted, nonanemic women.
Am J Clin Nutr. 2003
4. Trotti LM, Bhadriraju S, Becker LA.
Iron for Restless Legs.
Cochrane Database Syst Rev. 2012
5. Ridefelt P, Larsson A, Rehman JU, Axelsson J.
Influences of sleep and the circadian rhythm on iron-status indices.
Clin Biochem. 2010 Nov
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