When is the best time to take iron supplements?

When to Take Iron Supplements

Take iron supplements in the morning on an empty stomach with vitamin C (such as orange juice) for maximum absorption, and avoid taking them with coffee, tea, or meals. 1, 2, 3

Optimal Timing and Administration

Time of Day

• Morning dosing is superior to afternoon or evening administration because serum hepcidin (which blocks iron absorption) rises throughout the day and is further increased by morning iron doses 4, 3
• Afternoon dosing results in 37% lower iron absorption compared to morning administration due to elevated hepcidin levels 3

Relationship to Food

Take iron on an empty stomach (1 hour before or 2 hours after meals) for optimal absorption 1

• Taking iron with breakfast decreases absorption by 66% compared to taking it with water alone 3
• If gastrointestinal side effects occur with empty stomach dosing, consider alternate-day dosing rather than taking with food 1, 2

What to Take With Iron

Co-administer with 80 mg vitamin C (ascorbic acid) to enhance absorption 2, 3

• 80 mg of vitamin C increases iron absorption by 30% 3
• Higher doses (500 mg) provide no additional benefit 3
• Orange juice is an excellent practical source, providing approximately 90 mg of vitamin C and increasing iron absorption ~4-fold compared to taking iron with coffee or breakfast 3

What to Avoid

Do not consume coffee or tea within 1 hour of taking iron 2, 3

• Coffee alone decreases iron absorption by 54% 3
• Coffee with breakfast decreases absorption by 66%, even when vitamin C is present 3
• Tea contains tannins that similarly inhibit iron absorption 2

Dosing Frequency

Once-daily or alternate-day dosing is optimal rather than multiple daily doses 1, 2, 4

• Iron doses ≥60 mg stimulate hepcidin elevation that persists for 24 hours, blocking absorption of subsequent doses 4
• Alternate-day dosing (every other day) maximizes fractional iron absorption and reduces gastrointestinal side effects 1, 4
• If twice-daily dosing is prescribed, both doses should be taken in the morning, not split between morning and evening 4

Standard Dosing Regimens

Initial Treatment

• Start with one tablet daily of ferrous sulfate (65 mg elemental iron), ferrous fumarate, or ferrous gluconate 1, 2
• If side effects occur, reduce to one tablet every other day 1, 2
• Traditional recommendations of 100-200 mg daily in divided doses are less well-tolerated and may not improve absorption 1

Duration

Continue treatment for 3 months after hemoglobin normalizes to replenish iron stores 1, 2

Common Pitfalls to Avoid

• Don't take iron in divided doses throughout the day - this increases side effects without improving absorption due to hepcidin elevation 2, 4
• Don't assume higher doses are better - fractional absorption decreases with higher doses, and unabsorbed iron causes gastrointestinal side effects 4, 5
• Don't take iron with calcium supplements or antacids - these interfere with absorption 2
• Don't expect immediate results - hemoglobin should increase by 1 g/dL within 2 weeks in anemic patients 2

When Oral Iron Timing Doesn't Matter

Consider intravenous iron when oral iron fails, regardless of optimal timing strategies, in patients with: 2

• Intolerance to oral iron despite alternate-day dosing
• Malabsorption conditions (inflammatory bowel disease, celiac disease)
• Need for rapid iron repletion
• Ongoing blood losses exceeding oral replacement capacity