Magnesium Side Effects and Warnings

Safety Issues

The US government has set the following upper limits for use of magnesium supplements:

• Children

• 1-3 years: 65 mg

• 4-8 years: 110 mg

• Adults: 350 mg

• Pregnant or Nursing Women: 350 mg

In general, magnesium appears to be quite safe when taken at or below recommended dosages. The most common complaint is loose stools. However, people with severe kidney or heart disease should not take magnesium (or any other supplement) except on the advice of a physician. Maximum safe dosages have not been established for young children. There has been one case of death caused by excessive use of magnesium supplements in a developmentally and physically disabled child. ¹ Pregnant or nursing women should not exceed the nutritional dosages presented under Requirements/Sources .

If taken at the same time, magnesium can interfere with the absorption of antibiotics in the tetracycline family, ² and, possibly, the drug nitrofurantoin . ³ Also, when combined with oral diabetes drugs in the sulfonylurea family, magnesium may cause blood sugar levels to fall more than expected. ⁴

Interactions You Should Know About

If you are taking:

• Potassium supplements , manganese , loop and thiazide diuretics , oral contraceptives , estrogen-replacement therapy , cisplatin, digoxin , or medications that reduce stomach acid: You may need extra magnesium.

• Antibiotics in the tetracycline family or nitrofurantoin (Macrodantin): You should separate your magnesium dose from doses of these medications by at least 2 hours to avoid absorption problems.

• Oral diabetes medications in the sulfonylurea family (Tolinase, Micronase, Orinase, Glucotrol, Diabinese, DiaBeta): Work closely with your physician when taking magnesium to avoid hypoglycemia.

• Amiloride : Do not take magnesium supplements except on medical advice. ⁵