Magnesium plays a role in over 300 chemical reactions and is involved in muscle contraction, nerve signaling, heart function and bone health. About half of the magnesium in your body is found inside your bones, while most of the remaining magnesium is located inside your cells. Only 1 percent of magnesium is found in your blood, but this magnesium concentration must be kept at a constant level to keep your body functioning properly. If your doctor suspects the level of magnesium in your blood is abnormal, he or she may recommend a serum magnesium test to check magnesium blood levels.
When Testing Is Ordered
If you present symptoms of a magnesium deficiency, such as muscle cramps, twitching, muscle weakness, confusion, abnormal heart beat or seizures, your doctor may order a serum magnesium test. Your doctor may also recommend magnesium testing as a follow-up diagnostic test if your potassium or calcium levels are low. Magnesium testing is also ordered as a part of an evaluation for malnutrition, diarrhea, alcoholism and malabsorption disorders.
If you are on medications that trigger magnesium loss or have a chronic condition, such as diabetes or kidney disease, you may require regular serum magnesium testing to monitor magnesium blood levels.
Testing Procedure
During the magnesium test, your doctor or lab technician will prepare the testing site, which is usually the back of the hand or inner elbow, by cleaning the area with an antiseptic solution. Next, an elastic band is tied around the upper arm to increase pressure in the vein and make blood collection easier. Once the vein swells, a needle is inserted and blood is collected into a tube or vial attached to the needle. Once adequate amounts of blood are obtained, the needle is removed and blood is sent to the laboratory for testing.
Results
Normal magnesium levels fall between 1.7 to 2.2 mg/dL. Several situations and circumstances can increase or decrease your serum magnesium levels. Low magnesium levels may be a result of inadequate dietary magnesium intake, chronic diarrhea, uncontrolled diabetes, severe burns, chronic use of diuretics or hypoparathyroidism, which is characterized by underactive parathyroid glands. Magnesium levels may also fall directly after surgery.
Increased magnesium levels may be caused by kidney failure, dehydration, Addison's disease, hyperparathyroidism or hypothyroidism, which is characterized by an underactive thyroid gland. Excessive intake of magnesium does not usually lead to increased blood magnesium levels unless other conditions, such as kidney failure, are present as well.
Considerations
It may be necessary to fast overnight prior to having your magnesium levels tested. Make sure to follow any recommendations provided by your doctor. Straying from recommendations may cause abnormal results.
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