This is a blood test which measures the amount of magnesium in your blood. Most of the magnesium in your body exists in your cells. However, the magnesium in your blood is important for many processes. It is important for your nerves to be able to conduct electrical energy. This is important in heart patients with higher heartbeats. When your heart beats and then gets ready to beat again, it repolarizes. If the magnesium levels are low or high, it can affect the accuracy of the repolarization process. The magnesium levels are also monitored during pregnancy. This is done to determine if the expectant mother may have preeclampsia or toxemia. Magnesium is often used for treatment of these problems.


No preparation or fasting is needed. A blood sample may be taken by inserting a needle into a vein in the arm.


  • Adult: 1.3 to 2.1 mEq/L or 0.65 to 1.05 mmol/L (SI units)

  • Child: 1.4 to 1.7 mEq/L

  • Newborn: 1.4 to 2 mEq/L

Possible critical values: less than 0.5 mEq/L or greater than 3 mEq/L

Ranges for normal findings may vary among different laboratories and hospitals. You should always check with your caregiver after having lab work or other tests done to discuss the meaning of your test results and whether your values are considered within normal limits.


Your caregiver will go over the test results with you. Your caregiver will discuss the importance and meaning of your results. He or she will also discuss treatment options and additional tests, if needed.


It is your responsibility to obtain your test results. Ask the lab or department performing the test when and how you will get your results.