Calcium significantly reduces iron absorption when taken together.
Calcium and iron compete for the same absorption pathways in the intestine.
Take calcium and iron supplements at least 2 hours apart for optimal absorption of both.
Take calcium and iron at different times of day for optimal absorption.
Calcium inhibits both heme and non-heme iron absorption by up to 60%.
Take iron in the morning on an empty stomach with vitamin C. Take calcium at a different meal or before bed.
Known drug category interactions for these supplements. Especially relevant if you take prescription medications.
Calcium reduces levothyroxine absorption, potentially causing thyroid levels to fluctuate.
Take levothyroxine at least 4 hours before or after calcium supplements.
Iron reduces levothyroxine absorption.
Take levothyroxine at least 4 hours before or after iron supplements.
Reference values for safe daily intake of these supplements.
Excess may increase kidney stone risk and potentially cardiovascular risk.
GI distress above UL. Risk of iron overload in people with hemochromatosis.