When should I take a vitamin C (ascorbic acid) tablet relative to ferrous gluconate?

When to Take Ascorbic Acid (Vitamin C) with Ferrous Gluconate

Take your ascorbic acid tablet at the same time as your ferrous gluconate, in the morning on an empty stomach, and wait at least 2 hours before eating or drinking coffee.

Optimal Timing Strategy

The most effective approach is to take both supplements together first thing in the morning on an empty stomach. 1

• Morning dosing is superior to afternoon or evening administration because serum hepcidin (which blocks iron absorption) increases throughout the day and reduces absorption of doses taken later 1
• Wait at least 2 hours after taking the supplements before eating, as food consumed within 2 hours can reduce iron absorption by as much as 50% 2
• Ideally, take the supplements 1 hour before meals for best results 3

Vitamin C Dosing for Enhanced Absorption

Add 80-500 mg of ascorbic acid when taking ferrous gluconate to significantly enhance iron absorption. 1, 4

• 80 mg of ascorbic acid increases iron absorption by 30% 1
• Higher doses (500 mg) do not provide additional benefit beyond 80 mg 1
• The American Gastroenterological Association recommends approximately 500 mg of vitamin C with iron supplements, especially if taking with meals 3
• A molar ratio of 2:1 (ascorbic acid to iron) is effective for meals with low to medium levels of absorption inhibitors 4

Critical Substances to Avoid

Do not consume coffee, tea, or calcium-containing foods within 1-2 hours of taking your iron and vitamin C. 3

• Coffee decreases iron absorption by 54% when taken with iron 1
• Coffee with breakfast decreases absorption by 66%, even in the presence of ~90 mg of ascorbic acid 1
• Tea is also a powerful inhibitor of iron absorption and should be avoided within 1 hour after taking iron 3
• Aluminum-based antacids or phosphate binders can reduce iron absorption 2

Practical Dosing Schedule

Take one ferrous gluconate tablet (325 mg, containing 35 mg elemental iron) with 80-500 mg of ascorbic acid in the morning on an empty stomach. 2, 1

• Once-daily dosing is superior to multiple daily doses because iron doses ≥60 mg stimulate hepcidin elevation that persists for 24 hours and blocks absorption of subsequent doses 3
• If you experience significant gastrointestinal side effects, consider alternate-day dosing (every other day), which significantly increases fractional iron absorption while reducing side effects 3
• Oral iron is best absorbed when ingested without food or other medications 2

Alternative Strategy if Morning Fasting is Difficult

If taking supplements on an empty stomach causes intolerable side effects, you can take them with a small amount of vitamin C-rich food (like orange juice), though this reduces absorption somewhat 1, 4:

• Consuming iron with orange juice alone (containing ~90 mg ascorbic acid) results in approximately 4-fold increase in iron absorption compared to taking it with coffee or breakfast 1
• This provides ~20 more mg of absorbed iron per dose compared to taking with coffee or meals 1

Monitoring Response

• Check hemoglobin at 4 weeks to assess response to therapy 3
• Continue treatment for approximately 3 months after hemoglobin normalizes to adequately replenish iron stores 3
• The absence of a hemoglobin rise of at least 10 g/L after 2 weeks strongly predicts treatment failure 3

Common Pitfalls to Avoid

• Do not take iron more than once daily unless using alternate-day dosing, as multiple daily doses increase side effects without improving absorption 3
• Do not consume the supplements with meals, coffee, or tea as this dramatically reduces absorption even in the presence of vitamin C 1
• Do not discontinue therapy when hemoglobin normalizes—continue for 3 months to replenish iron stores 3
• Do not take iron in the afternoon or evening when hepcidin levels are higher 1