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Magnesium oxide Side Effects

Applies to magnesium oxide: oral capsule, oral tablet.


Before you take magnesium oxide, tell your doctor about all your medical conditions or allergies, and all the medicines you are using. Also make sure your doctor knows if you are pregnant or breast-feeding. In some cases, you may not be able to take magnesium oxide, or you may need a dose adjustment or special precautions.

Get emergency medical help if you have signs of an allergic reaction: hives; difficult breathing; swelling of your face, lips, tongue, or throat.

Stop using magnesium oxide and call your doctor at once if you have:

  • rectal bleeding;

  • coughing up blood or vomit that looks like coffee grounds;

  • bloody or tarry stools; or

  • no bowel movement after using magnesium oxide as a laxative.

Common side effects may include:

This is not a complete list of side effects and others may occur. Call your doctor for medical advice about side effects.

For Healthcare Professionals

Applies to magnesium oxide: compounding powder, oral capsule, oral tablet.


Magnesium toxicity symptoms may include: hypotension, nausea, vomiting, facial flushing, urine retention, ileus, depression, lethargy, muscle weakness, respiratory depression, arrhythmia, cardiac arrest, coma, and death.[Ref]

Frequency not reported: Hypermagnesemia, magnesium toxicity[Ref]


Frequency not reported: Diarrhea, nausea, abdominal cramping[Ref]


1. Guerrera MP, Volpe SL, Mao JJ. Therapeutic uses of magnesium. Am Fam Physician. 2009;80:157-62.

2. National Institutes of Health (NIH). Magnesium: fact sheet for health professionals. 2017.

Further information

Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.

Some side effects may not be reported. You may report them to the FDA.