Calcium blocks iron absorption. Learn why, how long to wait between doses, and the best schedule for taking both supplements.
Calcium can inhibit iron absorption when taken together.
Recommendation: Take at least 2 hours apart.
Calcium can inhibit iron absorption when taken together.
Tip: Take at least 2 hours apart.
| Standard | calcium | iron |
|---|---|---|
| US (FDA) | 1000 / 2500 mg (RDA/UL) | 18 / 45 mg (RDA/UL) |
| EU (EFSA) | 1000 / 2500 mg (RDA/UL) | 18 / 45 mg (RDA/UL) |
| AU (TGA) | 1000 / 2500 mg (RDA/UL) | 18 / 45 mg (RDA/UL) |
| CN (CNS) | 800 / 2000 mg (RDA/UL) | 20 / 42 mg (RDA/UL) |
| JP (MHLW) | 800 / 2300 mg (RDA/UL) | 10.5 / 50 mg (RDA/UL) |
Values shown as RDA (Recommended Dietary Allowance) / UL (Tolerable Upper Intake Level). Sources: NIH, FDA, EFSA, FSANZ, CNS, MHLW.
Calcium competes with iron for absorption. Even small amounts of calcium (as little as 50 mg) can reduce iron absorption by up to 50%.
Wait at least 2 hours. Take iron in the morning on an empty stomach and calcium in the evening with a meal.
This page only checks one pair. Use NutriAudit to check your full supplement stack for interactions, duplicates, and safe dosages.
Not medical advice. Always consult a qualified healthcare professional for personal medical decisions.