What is the best way to take iron supplements?

How to Take Iron Supplements

Take 50-100 mg of elemental iron (one ferrous sulfate 200 mg tablet) once daily in the morning on an empty stomach with 500 mg of vitamin C, and avoid coffee, tea, or calcium-containing foods for 1-2 hours before and after the dose. 1

Optimal Iron Formulation

• Ferrous sulfate is the first-line choice as it is the most cost-effective option (approximately £1.00 per 28-day supply) and equally effective as other formulations 2, 3
• A standard 200 mg ferrous sulfate tablet provides 65 mg of elemental iron 1, 3
• Alternative ferrous salts (ferrous fumarate or ferrous gluconate) can be tried if ferrous sulfate causes intolerable side effects, though evidence for improved tolerability is limited 2, 3

Dosing Strategy: Once Daily is Superior

• Take iron once daily, not multiple times per day - doses ≥60 mg stimulate hepcidin elevation that persists for 24 hours and blocks absorption of subsequent doses 1, 4
• Taking 60 mg twice daily provides no additional absorption benefit compared to 60 mg once daily, with 35-45% reduction in absorption from the second dose 3
• The traditional approach of split dosing (2-3 times daily) is unnecessary and actually decreases total absorption while increasing side effects 1, 4

Timing: Morning on Empty Stomach

• Take iron in the morning rather than afternoon or evening - serum hepcidin increases during the day and reduces absorption 1
• Take 1-2 hours before or after meals for maximum absorption 1, 3
• Food consumed within 2 hours before or 1 hour after iron can reduce absorption by up to 50% 1

Enhancing Absorption

• Take with 500 mg of vitamin C (ascorbic acid) to significantly enhance absorption, especially if you need to take it with food 1, 4
• Consuming iron with meat protein can improve absorption 1

What to Avoid

• Do not take iron with tea or coffee - these are powerful inhibitors of iron absorption and should be avoided for at least 1 hour after taking iron 1
• Avoid calcium-containing foods or supplements within 1-2 hours of iron 1, 3
• Do not take with aluminum-based antacids or phosphate binders 1, 3
• Avoid taking within 2 hours of certain antibiotics 5

If Standard Dosing Causes Side Effects

• Consider alternate-day dosing (every other day) with 100-200 mg elemental iron - this significantly increases fractional iron absorption and reduces gastrointestinal symptoms 2, 4
• Alternate-day dosing works because hepcidin elevation subsides by 48 hours, allowing better absorption of the next dose 4
• If severe side effects occur, taking with small amounts of food may improve tolerance, though this reduces absorption 1
• Starting with a lower dose and gradually increasing can help if experiencing significant gastrointestinal side effects 1

Monitoring Your Response

• Expect hemoglobin to rise by at least 10 g/L (1 g/dL) within 2 weeks - failure to achieve this strongly predicts treatment failure (sensitivity 90.1%, specificity 79.3%) 2, 3
• Check hemoglobin at 4 weeks to confirm adequate response 1, 3
• Continue treatment for approximately 3 months after hemoglobin normalizes to adequately replenish iron stores, not just correct anemia 2, 1, 3

When to Consider Intravenous Iron

• If oral iron causes intolerable gastrointestinal symptoms despite dosing adjustments 1, 3
• If hemoglobin fails to rise after 2-4 weeks of adherent oral therapy 1, 3
• If you have conditions impairing oral iron absorption (inflammatory bowel disease, prior gastric surgery, chronic kidney disease) 1, 3
• IV iron can produce clinically meaningful hemoglobin response within one week 3

Common Pitfalls to Avoid

• Do not take more than once daily - this increases side effects without improving absorption due to hepcidin elevation 1
• Do not use modified-release or enteric-coated formulations - these are less suitable for prescribing and decrease absorption 3
• Do not rely on multivitamin preparations, which typically contain insufficient elemental iron (up to 14 mg) for treating iron deficiency 3
• Do not switch between different ferrous salts expecting better tolerability - this is not supported by evidence 2, 3
• Do not discontinue therapy prematurely - improvement in hemoglobin occurs within weeks, but complete iron store repletion takes months 1