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Serum Magnesium Test

What Is a Serum Magnesium Test?

Magnesium is important to the functioning of your body. According to the National Institutes of Health (NIH), this mineral plays a role in more than 300 of your body’s biochemical reactions. For example, it helps regulate blood pressure and your heartbeat. It also helps maintain bone strength. Having too little magnesium in your body can negatively affect all of these functions.

Many common foods contain magnesium. Rich magnesium sources include:

  • green vegetables, such as spinach
  • nuts
  • seeds
  • beans

Your tap water may also contain magnesium.

It’s possible to have too much magnesium. In rare cases, magnesium overdoses can lead to cardiac arrest and death. It’s rare to overdose on magnesium through food alone. Instead, magnesium overdose may be due to taking too many magnesium supplements.

You might need to take supplements if you have certain conditions such as diabetes, alcoholism, or an issue absorbing nutrients. You may also take them if you have low potassium and calcium levels in your blood.

If your doctor suspects that your magnesium level is too low or too high, they may order a serum magnesium test.

This test involves a basic blood draw. Your doctor will collect some of your blood into a vial or tube and send it to a lab for testing.

Why Do I Need a Serum Magnesium Test?

Your doctor may order a serum magnesium test if they suspect your magnesium level is too low or too high. Either extreme can lead to health problems. This test may also be ordered if you have chronic low potassium and calcium levels. Magnesium plays a role in regulating the calcium and potassium levels in your body. Your doctor may check your magnesium if these levels are consistently low.

This test may also be necessary if your doctor thinks you might have a malabsorption or malnutrition problem. You may have this test regularly if you have diabetes or kidney problems. This helps your doctor stay on top of your condition.

Symptoms of magnesium deficiency initially include:

  • appetite loss
  • fatigue
  • nausea
  • vomiting
  • weakness

As the deficiency progresses, you may experience:

  • numbness and tingling
  • seizures
  • muscle cramps
  • personality changes
  • abnormal heart rhythms

The signs and symptoms of an overdose include:

  • confusion
  • diarrhea
  • nausea
  • slowed heart rate
  • upset stomach
  • vomiting
  • very low blood pressure

On rare occasions, cardiac arrest or death from a magnesium overdose can occur.

Your doctor might order this test if your symptoms suggest either a magnesium deficiency or an overdose.

The NIH provides a list of foods high in magnesium. Wheat bran, dry roasted almonds, and cooked frozen spinach are at the top of the list. Each one of these foods provides only about 20 percent of your daily value of magnesium per serving.

It would be hard to eat too much magnesium. Overdoses usually happen when someone consumes too much supplemental magnesium. You may take supplements if you have diabetes or alcoholism. Your doctor may also instruct you to take them if you have Crohn’s disease.

What Are the Risks Associated with the Serum Magnesium Test?

You can expect to feel some minor pain during a blood draw. You might also continue to bleed slightly for a few minutes after the procedure. You may get a bruise at the needle insertion site.

Serious risks are rare and include fainting, infection, and inflammation.

What Do the Results Mean?

The normal range for serum magnesium is 1.7 to 2.3 milligrams per deciliter.

The exact standards for normal results may vary depending on your:

  • age
  • health
  • body type
  • sex

The standards also depend on the lab performing the test.

Discuss your results with your doctor to get more precise information.

High levels of magnesium usually are not a result of consuming too much as part of your diet. Instead, they often result from having too many supplements. In other cases, high levels are due to a problem with excreting extra magnesium.

Specific conditions that can lead to high magnesium levels include:

  • Addison’s disease, which is a disorder of the adrenal glands
  • dehydration
  • thyroid issues including hypothyroidism or hyperparathyroidism
  • diabetic acidosis
  • kidney failure
  • oliguria, or low urine production

Low levels, on the other hand, can indicate that you don’t eat enough of this mineral. Sometimes, low levels mean that your body isn’t keeping enough of the magnesium that you eat. This can happen in cases of:

  • chronic diarrhea
  • hemodialysis, which is a mechanical way to filter waste products from the blood when the kidneys don’t function properly
  • gastrointestinal disorders, such as Crohn’s disease, which is an inflammation of the bowel
  • ongoing use of diuretics

There are quite a few other possible causes of low magnesium. These include:

  • heavy periods
  • issues with specific conditions, including hepatic cirrhosis, hyperaldosteronism, and hypoparathyroidism
  • severe burns
  • pancreatitis
  • excessive sweating
  • toxemia of pregnancy
  • ulcerative colitis, which is an inflammation of the bowel that affects the large intestine
  • uncontrolled diabetes

Low levels can also occur in alcoholism and during the course of a condition caused by alcohol withdrawal called "delirium tremens," which involves trembling, agitation, and hallucinations.

High and low magnesium levels have a wide variety of causes. You should work with your doctor to find out the cause of your symptoms.

Content licensed from:

Written by: Gretchen Holm
Medically reviewed on: Dec 18, 2015: Mark R Laflamme MD

This feature is for informational purposes only and should not be used to replace the care and information received from your health care provider. Please consult a health care professional with any health concerns you may have.
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