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Magnesium is an essential mineral to the human body. It is needed for bone, protein, and fatty acid formation, making new cells, activating B vitamins, relaxing muscles, clotting blood, and forming adenosine triphosphate (ATP; the energy the body runs on). The secretion and action of insulin also require magnesium.

Where is it found?

Nuts and grains are good sources of magnesium. Beans, dark green vegetables, fish, and meat also contain significant amounts.

Magnesium has been used in connection with the following conditions (refer to the individual health concern for complete information):

Science Ratings Health Concerns

Cardiac arrhythmia

Congestive heart failure


Gestational hypertension

Kidney stones (citrate in combination with potassium citrate)

Migraine headaches

Mitral valve prolapse

Type 1 diabetes

Type 2 diabetes



Anemia (for thalassemia)



Celiac disease (for deficiency only)

Heart attack (IV magnesium immediately following a myocardial infarction)

High blood pressure (for people taking potassium-depleting diuretics)


Premenstrual syndrome

Urinary urgency (women)


Alcohol withdrawal support


Athletic performance


Chronic fatigue syndrome

Chronic obstructive pulmonary disease (COPD)

Cluster headache (intravenous)



Heart attack (oral magnesium)

High cholesterol



Insulin resistance syndrome (Syndrome X)

Intermittent claudication

Multiple sclerosis


Raynaud’s disease


Sickle cell anemia


3Stars Reliable and relatively consistent scientific data showing a substantial health benefit.
2Stars Contradictory, insufficient, or preliminary studies suggesting a health benefit or minimal health benefit.
1Star For an herb, supported by traditional use but minimal or no scientific evidence. For a supplement, little scientific support and/or minimal health benefit.

Who is likely to be deficient?

Magnesium deficiency is common in people taking “potassium-depleting” prescription diuretics. Taking too many laxatives can also lead to deficiency. Alcoholism, severe burns, diabetes, and heart failure are other potential causes of deficiency. In a study of urban African-American people (predominantly female), the overall prevalence of magnesium deficiency was 20%. People with a history of alcoholism were six times more likely to have magnesium deficiency than were people without such a history.1 The low magnesium status seen in alcoholics with liver cirrhosis contributes to the development of hypertension in these people.2

Almost two-thirds of people in intensive care hospital units have been found to be magnesium deficient.3 Deficiency may also occur in people with chronic diarrhea, pancreatitis, and other conditions associated with malabsorption.

Fatigue, abnormal heart rhythms, muscle weakness and spasm, depression, loss of appetite, listlessness, and potassium depletion can all result from a magnesium deficiency. People with these symptoms should be evaluated by a doctor before taking magnesium supplements.

As previously mentioned, magnesium levels have been found to be low in people with chronic fatigue syndrome.

Deficiencies of magnesium that are serious enough to cause symptoms should be treated by medical doctors, as they might require intravenous administration of magnesium.4

How much is usually taken?

Most people don’t consume enough magnesium in their diets. Many nutritionally oriented doctors recommend 250–350 mg per day of supplemental magnesium for adults.

Are there any side effects or interactions?

Comments in this section are limited to effects from taking oral magnesium. Side effects from intravenous use of magnesium are not discussed.

Taking too much magnesium often leads to diarrhea. For some people this can happen with amounts as low as 350–500 mg per day. More serious problems can develop with excessive magnesium intake from magnesium-containing laxatives. However, the amounts of magnesium found in nutritional supplements are unlikely to cause such problems. People with kidney disease should not take magnesium supplements without consulting a doctor.

Vitamin B6 increases the amount of magnesium that can enter cells. As a result, these two nutrients are often taken together. Magnesium may compete for absorption with other minerals, particularly calcium. Taking a multimineral supplement avoids this potential problem.

Are there any drug interactions?
Certain medicines may interact with magnesium. Refer to drug interactions for a list of those medicines.


1. Fox CH, Ramsoomair D, Mahoney MC, et al. An investigation of hypomagnesemia among ambulatory urban African Americans. J Fam Pract 1999;48:636–9.

2. Kisters K, Schodjaian K, Tokmak F, et al. Effect of ethanol on blood pressure—role of magnesium. Am J Hypertens 2000;13:455–6 [letter].

3. Weisinger JR, Bellorin-font E. Magnesium and phosphorus.Lancet 1998;352:391–6 [review].

4. Weisinger JR, Bellorin-font E. Magnesium and phosphorus.Lancet 1998;352:391–6 [review].

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