Can you take Calcium and Magnesium together?

NoteMechanism-based

Yes, at normal doses. At high calcium doses, spacing them out is a reasonable precaution.

What to do: No action needed at typical doses. If you take ≥1,000 mg calcium from supplements, take magnesium at a different time (e.g. bedtime).

Dose matters: At ≥1,000 mg supplemental calcium, spacing calcium and magnesium becomes more worthwhile.

Very high calcium may reduce magnesium absorption

Calcium and magnesium share some intestinal transport and renal handling. Human data are mixed, and combination products at usual doses are generally fine.

Evidence level: Mechanism-based — Plausible biological mechanism with little direct human outcome data.

Sources

  1. NIH Office of Dietary Supplements — Magnesium Fact Sheet for Health Professionals
  2. NIH Office of Dietary Supplements — Calcium Fact Sheet for Health Professionals

Suggested timing for Calcium and Magnesium

Dinner

~19:00

Bedtime

~22:30

Taking more than these two?

Add the rest of your stack and your medications for a complete check and timing plan.

Check my full stack

Buying guide

What to look for on the label

Form and quality matter as much as dose.

  • Calcium

    • • Calcium citrate (absorbs with or without food)
    • • Calcium carbonate (cheaper, must be taken with food)

  • Magnesium

    • • Magnesium glycinate (well tolerated, popular for sleep)
    • • Magnesium citrate (also a mild laxative)
    • • Avoid magnesium oxide if absorption matters

Related interactions

Calcium + IronCalcium reduces iron absorption from the same mealCalcium + ZincCalcium may modestly lower zinc absorptionCalcium + Vitamin D3Vitamin D increases calcium absorptionCalcium + Vitamin K2K2 helps direct calcium into boneCalcium + Psyllium HuskFiber can reduce calcium absorptionMagnesium + ZincVery high zinc can reduce magnesium absorption

Learn more about Calcium and Magnesium.