What should be taken with iron supplements to enhance absorption?

Enhancing Iron Absorption with Vitamin C

Add vitamin C (approximately 500 mg) to your iron supplement to significantly improve absorption. 1

Primary Recommendation

The American Gastroenterological Association explicitly recommends adding vitamin C to oral iron supplementation to enhance absorption 1. This is considered a Best Practice Advice based on the well-established role of vitamin C as the most potent enhancer of non-heme iron absorption 2, 3.

Optimal Vitamin C Dosing

• Take approximately 500 mg of vitamin C with your iron supplement 2, 3
• This dose is effective even when iron is taken with meals containing calcium or fiber, which would otherwise inhibit absorption 2
• Vitamin C works by reducing ferric iron to ferrous iron (the more absorbable form) and preventing formation of insoluble iron compounds 3, 4

Practical Sources of Vitamin C

• Vitamin C supplements (500 mg) provide the most reliable dose 2, 3
• Citrus fruits and juices can be used as natural sources 3
• A small glass of unsweetened orange juice contains sufficient vitamin C to enhance iron absorption 3
• Taking iron with 80 mg or more of ascorbic acid on an empty stomach significantly improves absorption 3

Additional Strategies to Maximize Absorption

• Take iron on an empty stomach when possible for optimal absorption 2, 3
• If you must take iron with food (due to stomach upset), pair it with meat protein, which also enhances absorption 2
• Take iron only once daily, as more frequent dosing increases side effects without improving absorption due to hepcidin elevation 1, 2
• Consider every-other-day dosing, which may be equally effective with better tolerability 1

Critical Substances to Avoid

• Do not take iron with calcium-containing foods or supplements (dairy products, calcium pills) 2
• Avoid fiber-containing foods when taking iron 2
• Do not consume tea or coffee within one hour of taking iron, as these are powerful inhibitors that can decrease absorption by up to 54% 3
• Avoid aluminum-based antacids or phosphate binders 2

Important Caveats

• If you have hemochromatosis or iron overload conditions, do NOT take vitamin C with iron, as it can accelerate iron deposition and worsen organ damage 3, 5
• If gastrointestinal side effects are intolerable with fasting administration, taking iron with food (plus vitamin C) is acceptable—the trade-off of reduced absorption is preferable to non-adherence 3, 6
• The FDA label notes that occasional gastrointestinal discomfort may be minimized by taking iron with meals 6

Evidence Quality Note

While the American Gastroenterological Association acknowledges that supporting evidence for vitamin C co-administration is somewhat limited 3, the physiological mechanism is well-established 7, 4, and the practice is widely recommended in current guidelines 1, 2, 3. A 2023 meta-analysis showed mixed results 8, but the biological plausibility and safety profile support this recommendation, particularly given vitamin C's dual role in both enhancing absorption and providing antioxidant protection against potential iron-induced oxidative stress 9.