What are the signs of too much magnesium?
Loose stools are the first and most reliable sign you are taking too much magnesium from supplements. Nausea, flushing, and low blood pressure can follow at very high doses. True toxicity is rare in healthy adults — the kidneys excrete the excess.
Last updated 27 June 2026
Safe upper limit
350 mg of supplemental elemental magnesium per day is the EFSA/NIH tolerable upper limit, in addition to food. Higher doses are used clinically (constipation, migraine) but should be guided by a clinician.
When to be cautious
Anyone with significant kidney disease (eGFR < 30) should not take magnesium supplements without medical supervision — the kidneys are the only route for clearance.
Frequently asked
- Can magnesium cause heart problems?
- Only at very high doses in people with kidney failure. Healthy hearts tolerate dietary doses well.
- I get loose stools — what now?
- Drop dose by 100 mg or switch from citrate/oxide to glycinate.
Educational content — not medical advice. Health claims comply with EU Regulation 1924/2006 and the Union Register of authorised claims (Regulation 432/2012). Food supplements are not a substitute for a varied, balanced diet and a healthy lifestyle. Always consult your GP or pharmacist before changing supplements, particularly if you take prescription medication or have kidney disease.