Magnesium, referred to as Mg on the periodic table of elements,1is a common component of lightweight metals and is the fourth most abundant mineral in the body.Seawater is rich in magnesium.

A number of health problems have been linked with low intakes and blood levels of magnesium, including type 2 diabetes, metabolic syndrome, elevated C-reactive protein, hypertension, atherosclerotic vascular disease, sudden cardiac death, osteoporosis, migraine headache, asthma, and colon cancer.3

Magnesium serves as an essential catalyst and enzyme cofactor for more than 300 necessary bodily functions.43

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Magnesium was discovered in 1755 by Dr. Joseph Black.1The normal range of magnesium is dependent on measurement method. For serum, a range of 1.7 to 2.2 mg/dL is considered normal.5

However, because 99% of the body’s total magnesium is intracellular, serum measurement does not provide a true picture. Measurement of red blood cell magnesium concentration (normal range 4.04–6.9 mg/dL) more closely reflects the true magnesium load.5


The mechanism of magnesium action in cardiac arrhythmias, migraines, and asthma appears to be its ability to calm membrane excitability by altering the resting membrane potential.6Multiple large trials have verified the positive effect of magnesium on vascular disease. 

In one meta-analysis of 22 studies and more than 1,100 patients with either normal or elevated blood pressure, participants given magnesium supplementation for an average of 3 months showed reductions in systolic blood pressure of 3 to 4 mmHg and in diastolic blood pressure of 2 to 3 mmHg.7 

In another analysis, normal serum magnesium levels correlated with a 30% lower risk of cardiovascular disease and a 22% lower risk of ischemic heart disease.8

For migraine management, studies involving both acute treatment with intravenous magnesium and preventive therapy with daily magnesium supplementation have demonstrated efficacy. 

However, the Quality Standards Subcommittee of the American Academy of Neurology and the American Headache Society deemed magnesium to be “probably” effective in the management of migraine headaches.9

In type 2 diabetes, magnesium deficiency worsens insulin resistance.10Then, as blood glucose levels rise, urinary excretion of magnesium increases,10creating a vicious cycle. 

A retrospective review involving 286,668 persons and 10,912 cases of type 2 diabetes uncovered a statistically significant, linear association between magnesium and the incidence of type 2 diabetes.11

In asthma, magnesium is often used as an abortive agent in acute bronchospasm due to its bronchodilatory action. In addition, one study showed that a 100 mg/day higher intake of magnesium yielded a forced expiratory volume in 1 second (FEV1) that was 27.7 mL higher.12

Finally, magnesium supplementation is garnering interest in the treatment of refractory depression. The element acts as a key neurotransmitter that strengthens synaptic function.13In vivo studies of patients with known refractory depression have shown a reduction in (intracellular) magnesium.14

Safety, how supplied, cost: 

Those who need to enhance their dietary intake of magnesium (almonds and spinach are particularly good sources)15might turn to supplements. 

Magnesium supplementation is generally safe (the recommended maximum supplemental dose for a healthy adult is 30 mg/day15), but toxicity can occur.

Supplemental magnesium is supplied as a pill or capsule, and in multiple forms. Magnesium oxide, hydroxide, chloride, carbonate, and sulfate are common, but magnesium gluconate or lactate is better absorbed. A month’s supply costs about $20.

Dose, interaction 

Because magnesium and calcium are antagonistic, supplements combining the two should be avoided. Those that are used should contain a 2:1 ratio of calcium to magnesium.16 

Long-term use of antacids, some antibiotics, and diuretics reduce gastric absorption and increase excretion. Esomeprazole magnesium and lansoprazole are among the prescription proton pump inhibitors that can cause hypomagnesemia.15

Magnesium can form insoluble complexes with some tetracycline and quinolone antibiotics.15Some diuretics, such as furosemide, can increase the loss of magnesium in urine, leading to magnesium depletion, whereas others—for example, spironolactone—can reduce magnesium excretion.15 

Magnesium can decrease the absorption of alendronate and other oral bisphosphonates.

Sherril Sego, FNP-C, DNP, is a staff clinician at the VA Hospital in Kansas City, Mo., where she practices adult medicine and women’s health. She also teaches at the nursing schools of the University of Missouri and the University of Kansas.


  1. Los Alamos National Laboratory. Periodic Table of Elements: LANL. Available at

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  12. Noppen M. Magnesium treatment for asthma: where do we stand? Chest . 2002;122(2):396-398.
  13. Nechifor M. Magnesium in major depression. Magnes Res. 2009;22(3):163S-166S.
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  15. National Institutes of Health. Magnesium: A fact sheet for health professionals. Updated November 4, 2013. 

  16. Kazaks AG, Uriu-Adams JY, Albertson TE, et al. Effect of oral magnesium supplementation on measures of airway resistance and subjective assessment of asthma control and quality of life in men and women with mild to moderate asthma: a randomized placebo controlled trial. 2010;47[1]:83-92.