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Blood Test: Magnesium

What Is a Blood Test?


What Is a Magnesium Test?

A magnesium test measures the amount of magnesium in the blood. Magnesium is a mineral that helps muscles, nerves, the immune system, and the heart work as they should. It also helps make protein and energy, and helps keep bones strong.

Why Are Magnesium Tests Done?

A magnesium test may be done if a person has signs of low magnesium levels, such as weakness, muscle cramps or twitching, or an abnormal heartbeat. It also might be done if someone has a medical condition that makes low magnesium levels more likely, such as a kidney problem.

How Should I Prepare for a Magnesium Test?

You should be able to eat and drink normally unless you're also getting other tests that require fasting beforehand. Tell your doctor about any medicines you take because some drugs might affect the test results.


How Is a Magnesium Test Done?

Usually, the blood is drawn from a vein in your arm — most often on the inside of the elbow, but sometimes on the back of the hand. To do that, a health professional will:

  • clean the skin
  • pull the blood sample into a vial or syringe


How Long Does a Magnesium Test Take?


What Happens After a Magnesium Test?


When Are Magnesium Test Results Ready?


Are There Any Risks From Magnesium Tests?



If you have questions about the magnesium test, speak with your doctor or the health professional doing the blood draw.