Very high doses of calcium may reduce magnesium absorption.
Both minerals compete for absorption pathways at high doses.
At normal supplemental doses this is usually not clinically significant. Separate by 2 hours if taking high doses of both.
Known drug category interactions for these supplements. Especially relevant if you take prescription medications.
Magnesium binds to these antibiotics in the gut, significantly reducing their absorption and effectiveness.
Take magnesium at least 2 hours before or 4-6 hours after these antibiotics.
Calcium reduces levothyroxine absorption, potentially causing thyroid levels to fluctuate.
Take levothyroxine at least 4 hours before or after calcium supplements.
Reference values for safe daily intake of these supplements.
Excess may increase kidney stone risk and potentially cardiovascular risk.
UL is for supplemental magnesium only (not dietary). Diarrhea is the primary adverse effect.