Co-Administration with Oral Iron for Enhanced Absorption
Take oral iron with approximately 100 mg of vitamin C (such as a glass of orange juice) on an empty stomach in the morning to maximize absorption. 1
Vitamin C: The Primary Absorption Enhancer
Vitamin C is the most potent enhancer of non-heme iron absorption (the form found in all oral iron supplements), and the American Gastroenterological Association recommends adding vitamin C to oral iron supplementation as a Best Practice Advice. 1
The optimal dose is 100-500 mg of vitamin C taken simultaneously with iron, which can be provided as a tablet or through citrus juice (one glass of orange juice contains approximately 80-100 mg). 1, 2
Vitamin C works by forming a chelate with iron that prevents formation of insoluble iron compounds and by reducing ferric to ferrous iron, making it more absorbable. 1
Vitamin C becomes even more critical when iron must be taken with food for tolerability, as it allows iron absorption even when calcium or fiber is present in the meal. 1
Optimal Timing and Administration Strategy
Take iron once daily in the morning on an empty stomach (1-2 hours before meals), as hepcidin levels are lower in the morning and food can reduce absorption by up to 50%. 1, 3, 2
Wait at least 1-2 hours after taking iron before consuming food, coffee, tea, or calcium-containing products. 1, 4
Avoid taking iron more than once daily, as doses ≥60 mg stimulate hepcidin elevation that persists for 24 hours and blocks absorption of subsequent doses by 35-45%. 1, 4
Consider alternate-day dosing if gastrointestinal side effects are problematic, as this significantly increases fractional iron absorption while reducing side effects. 1, 4
Additional Absorption Enhancers
- Meat protein (meat, poultry, fish) enhances iron absorption and can be consumed with iron if taking it with meals is necessary for tolerability. 1, 3
Critical Substances to Avoid
Coffee and tea are powerful inhibitors of iron absorption (coffee decreases it by 54%) and should not be consumed within 1 hour after taking iron. 1, 4, 5
Avoid calcium-containing foods, dairy products, fiber-containing foods, antacids, H2 inhibitors, and proton pump inhibitors when taking iron, as these significantly impair absorption. 1, 4, 3, 2
Polyphenols (in certain vegetables) and phytates (in bran) also decrease iron absorption. 1, 5
Absolute Contraindication for Vitamin C
Patients with hemochromatosis or iron overload conditions must completely avoid vitamin C supplements with iron, as vitamin C accelerates iron mobilization and can cause cardiac arrhythmias, cardiomyopathy, and sudden death. 1
For hemochromatosis patients who require vitamin C for other medical reasons, limit supplementation to 500 mg daily only after physician discussion, and never during iron depletion therapy. 1
Practical Implementation
The European Society of Gastroenterology specifically recommends taking iron tablets with lime juice or other citrus juices containing vitamin C to enhance absorption. 1
A standard regimen is 50-100 mg elemental iron (one 200 mg ferrous sulfate tablet) taken once daily in the morning on an empty stomach with 100 mg vitamin C or a glass of orange juice. 1, 2
Monitor hemoglobin at 4 weeks to assess response, and continue treatment for approximately 3 months after hemoglobin normalizes to adequately replenish iron stores. 1, 4
Common Pitfalls to Avoid
Do not take iron multiple times daily, as this increases side effects without improving absorption due to hepcidin elevation. 1, 4, 3
Do not assume all iron formulations require different co-administration strategies—vitamin C enhances absorption of all non-heme iron supplements (ferrous sulfate, ferrous fumarate, ferrous gluconate). 1, 3
Do not use multivitamin preparations as the sole source of iron supplementation, as they typically contain insufficient elemental iron for treating iron deficiency. 3