Magnesium Supplements: Important Medication Interactions to Know
Magnesium is an essential mineral, but supplements can interfere with some medicines. That doesn’t mean you need to avoid magnesium altogether—it means the timing and dose may matter.
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Important interactions
Certain antibiotics: Magnesium can reduce absorption of tetracycline antibiotics such as doxycycline and quinolone antibiotics such as ciprofloxacin and levofloxacin. These medicines generally need to be separated from magnesium by specific intervals.
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Office of Dietary Supplements
Bisphosphonates: Medicines such as alendronate, used for osteoporosis, can be absorbed less effectively when taken too close to magnesium. NIH recommends separating them by at least 2 hours.
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Office of Dietary Supplements
Diuretics (“water pills”): Some diuretics increase magnesium loss through urine, while potassium-sparing diuretics can reduce magnesium excretion.
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Office of Dietary Supplements
Proton-pump inhibitors (PPIs): Long-term use of medicines such as omeprazole, lansoprazole, or esomeprazole can contribute to low magnesium levels.
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Office of Dietary Supplements
Levothyroxine: Magnesium-containing antacids and supplements can interfere with thyroid-hormone absorption. Check with your pharmacist about appropriate separation from levothyroxine.
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Kidney disease deserves special attention
Healthy kidneys normally remove excess magnesium. Reduced kidney function can increase the risk of magnesium accumulation and toxicity, so people with kidney disease should talk with their healthcare professional before taking magnesium supplements.
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Office of Dietary Supplements
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How much is too much?
For adults, the U.S. NIH sets an upper limit of 350 mg/day of magnesium from supplements and medications (not magnesium naturally present in food), unless a healthcare professional recommends otherwise. High supplemental doses can cause diarrhea, nausea, and abdominal cramping; extremely high amounts can cause serious heart problems.
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Office of Dietary Supplements
Bottom line: Don’t automatically stop a prescribed medicine or magnesium supplement. Instead, give your doctor or pharmacist your complete list of medications, vitamins, and supplements so they can check interactions and tell you exactly how to space the doses.
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