“Never Use Magnesium If You Take These Medications” — The Safer Truth
The word “never” is too strong. Magnesium supplements can interact with certain medicines, but in many cases the solution is simply to separate the doses rather than stop magnesium completely.
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Office of Dietary Supplements
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Be especially careful if you take:
Doxycycline and other tetracycline antibiotics — magnesium can bind the medicine and reduce its absorption.
Ciprofloxacin, levofloxacin, and other quinolone antibiotics — magnesium can also reduce absorption. NIH guidance recommends taking these antibiotics at least 2 hours before or 4–6 hours after magnesium.
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Office of Dietary Supplements
Alendronate and other oral bisphosphonates — magnesium can interfere with absorption; separate magnesium by at least 2 hours.
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Office of Dietary Supplements
Diuretics (“water pills”) — drugs such as furosemide and hydrochlorothiazide can change magnesium levels, so monitoring may be appropriate.
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Office of Dietary Supplements
Proton-pump inhibitors (PPIs) — long-term use of medicines such as omeprazole can actually lower magnesium levels, sometimes requiring medical monitoring or supplementation.
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Office of Dietary Supplements
What about levothyroxine?
Magnesium may interfere with absorption of some medicines, so if you take levothyroxine, it’s sensible to ask your pharmacist about appropriate spacing rather than taking the two together.
An important warning for older adults
If you have kidney disease, don’t start a magnesium supplement without medical advice. Healthy kidneys remove excess magnesium, whereas impaired kidney function can allow magnesium to accumulate. Very high levels can cause low blood pressure, breathing problems, abnormal heart rhythms, and other serious effects.
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Office of Dietary Supplements
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Also remember that magnesium isn’t found only in supplements. Milk of Magnesia, some antacids, and some laxatives contain substantial amounts of magnesium.
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Office of Dietary Supplements
Bottom line: Don’t stop a prescribed medicine—or start a magnesium supplement—based on an internet list. Have a pharmacist check your complete medication, supplement, and antacid/laxative list for interactions.
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