Magnesium Blood Test
A magnesium blood test measures the amount of magnesium in a sample of your blood.
A magnesium blood test measures the amount of magnesium in a sample of your blood. Magnesium is a mineral that you get from many kinds of foods you eat. Some examples include nuts, seeds, beans, fortified breakfast cereals, green leafy vegetables, and milk. Your body needs magnesium to help your muscles, nerves, and heart work properly. Magnesium also helps control blood pressure and blood glucose , also called blood sugar. It's important for building strong bones, and it supports your immune system . Magnesium is a type of electrolyte . Electrolytes are electrically charged minerals. They help control the amount of fluid and the balance of acids and bases (pH balance) in your body. Most of your body's magnesium is stored in your bones, organs, and other body tissue. Only a small amount is found in your blood. Your body tightly controls the amount of magnesium in your blood mainly through your: Kidneys. They filter extra magnesium from your blood and get rid of it through urine (pee). If your magnesium level is low, your kidneys limit the amount lost through urine. Intestines. They control how much magnesium you absorb from the foods you eat. Abnormal levels of blood magnesium can be caused by many different conditions. So, a magnesium test may be used to help diagnose a variety of disorders. Other names: Mg, Mag, Magnesium-Serum
Why is this test ordered? You may need a magnesium blood test if you have symptoms that could be caused by abnormal magnesium levels. Symptoms of low magnesium include: Loss of appetite Nausea and vomiting Fatigue and weakness Muscle cramps Numbness and/or tingling Irregular heartbeat (arrhythmia) Seizures (if magnesium levels are extremely low) Symptoms of high magnesium are much the same as symptoms of low magnesium. They may also include: Diarrhea Abdominal (belly) cramping Cardiac arrest from extremely high levels of magnesium You may also need to have your magnesium levels checked to monitor your health if you: Have a condition that's linked to abnormal magnesium levels, such as: Chronic kidney disease Diabetes that's not well controlled Alcohol use disorder Malabsorption syndrome Malnutrition Chronic (long-lasting) diarrhea Low levels of potassium and/or calcium Take medicine that can decrease magnesium levels, for example: Diuretics ("water pills") Certain antibiotics Proton pump inhibitors to reduce stomach acid Take medicine that can increase magnesium levels, for example: Aspirin Medicines that contain magnesium, such as laxatives for constipation and certain antacids for heartburn or gastroesophageal reflux disease (GERD) Lithium Are being treated with magnesium and/or calcium.
Clinical Interpretation
If the results of your magnesium blood test are abnormal, your provider will use your medical history and the results of other tests to diagnose the cause. Many different conditions can affect magnesium levels, so ask your provider to explain what your test results mean. In general, low magnesium levels may mean that: You're not getting enough magnesium in your diet. Older adults and people with alcohol use disorder or malnutrition are more likely to have this problem. Your body isn't able absorb magnesium, even if you eat the right amount. Causes of this problem include digestive disorders , such as Crohn's disease , or taking certain medicines. Your body is getting rid of too much magnesium. Causes include kidney problems, long-term diarrhea, and diabetes, which can cause frequent urination (peeing) if blood glucose levels are too high. Other health conditions linked to low magnesium include underactive parathyroid glands and pregnancy , which increases the need for magnesium. Higher than normal magnesium levels may mean that: You're getting too much magnesium from dietary supplements , laxatives, antacids, or certain prescription medicines. It's rare to get too much magnesium from food alone. Your body has a problem getting rid of magnesium. The most common cause is kidney failure. Other health conditions linked to high magnesium include dehydration , hypothyroidism , Addison disease , and overactive parathyroid glands. Treatment for abnormal magnesium levels will depend on your condition. Learn more about laboratory tests, reference ranges, and understanding results .
Clinical Protocol & Patient Advice
- 1
There's usually no preparation for a magnesium blood test. If you're having other blood tests at the same time, you may need to fast (not eat or drink) for several hours before your test. Your provider will let you know if you need to prepare for your test. Be sure to tell your provider about any prescription and over-the-counter medicines and/or supplements that you are taking.
Usage Guidance
- Reference ranges vary by laboratory. Always discuss your specific results with a qualified healthcare professional.
Source: MedlinePlus, National Library of Medicine. View the original.