“Anyone taking magnesium should be warned if they fall into these two groups”
This viral headline is partly true but oversimplified. Magnesium is an essential mineral, and magnesium from ordinary foods is generally safe. The bigger concern is magnesium supplements, antacids, and laxatives, particularly in certain people.
The two groups that deserve particular caution
1. People with kidney disease or reduced kidney function 🩺
The kidneys normally remove excess magnesium. If kidney function is significantly impaired, magnesium can accumulate and, at very high levels, cause low blood pressure, muscle weakness, difficulty breathing, abnormal heart rhythms, and potentially cardiac arrest.
If you have kidney disease, don’t start a magnesium supplement without discussing the dose with your clinician.
2. People taking certain medications 💊
Magnesium can interfere with absorption of some medicines, particularly:
- Certain antibiotics, including tetracyclines and quinolones
- Oral bisphosphonates used for osteoporosis
These medications generally need to be separated from magnesium by an appropriate interval. Diuretics and long-term proton-pump inhibitors can also affect magnesium levels.
How much is too much?
For healthy adults, the U.S. NIH sets an upper limit of 350 mg/day of magnesium from supplements and medications—this limit does not include magnesium naturally present in food. Higher doses may sometimes be medically appropriate under professional supervision.
Too much supplemental magnesium commonly causes diarrhea, nausea and abdominal cramping; extremely high amounts can be dangerous.
