How to Diagnose Magnesium Deficiency and Choose Supplements

Also known as the “master mineral”, magnesium is the fourth most abundant mineral in the body. It is involved in more than 300 biochemical reactions in the body, including muscle and nerve transmission, blood sugar control and blood pressure regulation. Magnesium helps make proteins, bones and even DNA in the body. It is vital for heart, brain, muscle, nerve and reproductive health. Based on the many functions of magnesium in the body, healthy levels of this mineral are needed to prevent and manage many diseases.

Magnesium deficiency has been associated with insulin resistance and Type 2 diabetes, heart diseases, high blood pressure, stroke, migraine headaches, attention deficit, hyperactivity disorder (ADHD), and Alzheimer’s disease.

Therefore it is important to recognize magnesium deficiency and correct it by consuming more magnesium-rich foods and take high quality magnesium supplements. Let’s find out how to diagnose magnesium deficiency, who is at risk to develop deficiency and the best magnesium supplements available on the market.

How to diagnose magnesium deficiency

There are special tests and also symptoms that suggest magnesium deficiency.

Normal magnesium concentrations in the blood range between 0.75 and 0.95 millimoles (mmol)/L. Hypomagnesemia (lower than normal levels of magnesium) is defined as a serum magnesium level of less than 0.75 mmol/L.

However, magnesium levels in the blood do not evaluate the true deficiency of magnesium. This is because only 1% of the total amount of magnesium is in the blood, and most of it is stored in the bones, soft tissues and inside the cells. An adult body contains about 25 mgs of magnesium, and the kidneys play important roles in the elimination of this mineral in the urine. If a person is deficient in magnesium, the kidneys will reduce the elimination of it in the urine.

Since magnesium levels in the blood have little correlation with the magnesium in the body, researchers looked into other tests. Magnesium concentrations in the red blood cells (RBCs) – which measure about 40% of the body’s magnesium – is an option. The normal value for this test is 4.2-6.8 mg/dL and some health experts suggest that ideally the levels should be between 6.0 and 6.5 mg/dL.

Other tests available to evaluate magnesium status include measuring the concentration of magnesium in saliva and urine, the levels of ionized magnesium concentration in blood or performing a magnesium tolerance test in which magnesium levels are measured in urine after a person receives intravenous magnesium.

At this point, researchers suggest that no lab tests are perfect. For best results, the tests should be used in combination with symptoms suggestive for magnesium deficiency described below.

Symptoms of magnesium deficiency

Many people do not have symptoms of magnesium deficiency in early stages, because the kidneys are able to limit the elimination of magnesium in the urine. However, long-term low intake of magnesium or excessive loss of this mineral due to certain conditions can lead to magnesium deficiency.

Some individuals may experience symptoms related to magnesium deficiency including loss of appetite, nausea, vomiting and general symptoms like fatigue and weakness. If the deficiency worsens, symptoms like tingling, numbness, muscle cramps occur. In severe cases, a shortage of magnesium can cause seizures, changes in personality, abnormal heart rhythms, and other heart complications.

Magnesium deficiency can also lead to other mineral imbalances including low levels of calcium and potassium in the blood.

Best magnesium supplements

The most common form of magnesium found in pharmacies and grocery stores is magnesium oxide, which is poorly absorbed (only 3 to 7% absorption). In addition, this form of magnesium is well known to have a laxative effect.

Magnesium glycinate and citrate are better absorbed (15 to 20% absorption).

Among the best magnesium supplements is Ionic magnesium because it has a very high absorption and is widely available in powder or liquid form.

Magnesium malate is another good, highly absorbable form, while magnesium threonate works best if you are looking to improve the levels of magnesium in the brain – for example if you want to prevent or better manage brain conditions like Alzheimer’s or Parkinson’s disease.

Magnesium works closely with other nutrients like vitamin D, K, B2, B3, B6 and boron. Therefore magnesium should be taken with foods or with a multivitamin / multimineral. Some studies also suggest magnesium can be taken before bedtime to improve the quality of sleep.

Most Americans do not consume enough magnesium

According to the National Institutes of Health, many Americans (as many as 48%, according to a large survey) consume less than recommended amounts of magnesium. Thus, supplements can help fill the gaps and prevent a deficiency in this mineral.

The current recommended daily amounts for magnesium are:

0-6 months30 mg30 mg
7-12 months75 mg75 mg
1-3 years80 mg80 mg
4-8 years130 mg130 mg
9-13 years240 mg240 mg
14-18 years410 mg360 mg400 mg360 mg
19-30 years400 mg310 mg350 mg310 mg
31-50 years420 mg320 mg360 mg320 mg
51+ years420 mg320 mg

Consider adding more magnesium rich foods like green leafy vegetables, legumes, nuts and seeds to your diet. If you have an app that provides the amount of magnesium and other nutrients from your diet, keep in mind that only 30% to 40% of magnesium from foods is absorbed by the body.

Who is at risk for magnesium deficiency?

Individuals with digestive conditions like celiac disease, Crohn’s disease and those who had surgeries of the gut, as well as those with diabetes, chronic alcoholism and elderly are at higher risk to develop magnesium deficiency.

Certain prescription drugs, particularly water pills (diuretics) and acid blockers like esomeprazole and lansoprazole, may also reduce magnesium levels in the body.

Key takeaways

Pay attention to your diet, and consider magnesium supplements if needed.

While consuming high magnesium-rich foods does not cause excess magnesium in the body, higher than recommended doses of magnesium supplements can cause diarrhea, nausea and abdominal cramps.

Choose magnesium supplements from a reputable company, which is fully transparent and lists all the ingredients on the label.

Choose a supplement that doesn't contain unnecessary fillers, artificial flavors or colors.


National Institutes of Health. Magnesium.

Grober, U., Schmidt, J., Kisters, K. (2015). Magnesium in Prevention and Therapy. Nutrients.

Dr. Carolyn Dean Live. (2016). Invisible Minerals: Magnesium.

US Food and Drug Administration. Low Magnesium Levels Can Be Associated With Long-Term Use of Proton Pump Inhibitor Drugs.

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