Magnesium (mg) test

This test checks the level of magnesium in your blood. Magnesium is an important electrolyte. It's needed for proper muscle, nerve, and enzyme function. It also helps the body make and use energy.

Most of the magnesium in the body is found in the bones and inside the cells. Only a tiny amount of magnesium is normally found in the blood.

A test for magnesium is done to:

• Find a cause for nerve and muscle problems, such as muscle twitches, irritability, and muscle weakness.
• Find the cause of symptoms such as low blood pressure, nausea, vomiting, diarrhea, dizziness, muscle weakness, and slurred speech.
• Monitor kidney function.
• Find the cause of heart problems or trouble breathing, especially in people who have kidney disease.
• Find the cause of a low calcium or potassium level that is not improving with treatment.
• Look for changes in magnesium levels caused by medicines, such as diuretics.
• See if people who have heart problems need extra magnesium. Low magnesium levels can increase the chances of life-threatening heart rhythm problems.
• Measure levels when magnesium is being given for medical treatment.

A health professional uses a needle to take a blood sample, usually from the arm.

Make sure to tell the doctor if your child takes:

• Antacids that contain magnesium.
• Laxatives (such as milk of magnesia or Epsom salts).
• Magnesium supplements.

Your child may have to stop taking them for a time before the test.

Each lab has a different range for what’s normal. Your lab report should show the range that your lab uses for each test. The normal range is just a guide. Your doctor will also look at your results based on your age, health, and other factors. A value that isn’t in the normal range may still be normal for you.

Many conditions can change magnesium levels. Your doctor will talk with you about any abnormal results that may be related to your symptoms and past health.