Magnesium Test: About This Test

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What is it?

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.

Why is this test done?

This test is used to find a cause for nerve and muscle problems. These include muscle twitches and weakness and irritability. It can see if people with heart problems need extra magnesium. Other uses are to check levels when magnesium is being given for medical treatment and check how well your kidneys are working.

How do you prepare for the test?

Don't take medicines containing magnesium for at least 3 days before this test. This includes:

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

How is the test done?

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

How long does the test take?

The test will take a few minutes.

What happens after the test?

  • You will probably be able to go home right away.
  • You can go back to your usual activities right away.

Follow-up care is a key part of your treatment and safety. Be sure to make and go to all appointments, and call your doctor if you are having problems. It's also a good idea to keep a list of the medicines you take. Ask your doctor when you can expect to have your test results.

Where can you learn more?

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The Health Encyclopedia contains general health information. Not all treatments or services described are covered benefits for Kaiser Permanente members or offered as services by Kaiser Permanente. For a list of covered benefits, please refer to your Evidence of Coverage or Summary Plan Description. For recommended treatments, please consult with your health care provider.