My magnesium is low — what should I do?
Serum magnesium underestimates total-body magnesium; RBC magnesium is more sensitive. Most adults benefit from 200–400 mg of glycinate or malate daily. Causes include diuretics, PPIs, alcohol, and GI loss.
Full answer
Serum magnesium reflects only ~1% of total-body magnesium and can be normal in true deficiency. RBC magnesium and clinical context (cramps, palpitations, sleep, blood pressure, glucose handling) refine the picture. Common drivers are diuretics, PPIs, alcohol, GI loss, and inadequate intake. Repletion is usually 200–400 mg daily of magnesium glycinate, malate, or threonate; oxide is poorly absorbed. Renal failure changes dosing. Magnesium supports glucose handling, blood pressure, sleep, and cardiac rhythm and is frequently co-deficient with vitamin D.
Educational. Not a substitute for individualized provider review.
- Methodology — Primary source · oMeds
- Reviewed by Dr. Laura Purdy, MD, MBA · Clinical Director, oMeds · Last reviewed 2026-06-03