Magnesium Test

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KEY POINTS

• This test measures the amount of magnesium in your child’s blood. Magnesium is important for your child’s nerves, digestive system, and heart to work well.
• This test may check certain medical conditions as a part of a larger picture that includes your child’s medical history, physical exam, and current health. It can also check how well treatment is working.
• Make sure your child follows your healthcare provider’s instructions about eating, drinking, and exercising before the test.

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What is the magnesium test?

This test measures the amount of magnesium in your child’s blood. Magnesium is an important nutrient for your child’s body. For example, your child’s nerves, digestive system, and heart all need it to work well. Your child can get magnesium from food and supplements.

Why is this test done?

This test may help diagnose and treat a medical problem your child is having. It does not diagnose a specific problem but it can help your child’s healthcare provider know what other tests your child might need. It may sometimes be used to see how well treatment is working.

This test may be done to look for or check certain medical conditions such as:

• Kidney disease
• Thyroid or parathyroid disease
• Heart rhythm problems
• Muscle problems such as twitching or cramping
• Low calcium, phosphorous, or potassium levels
• Nutrition, stomach, or intestine problems such as Crohn’s disease

How do I prepare my child for this test?

• Your child may need to avoid taking certain medicines before the test because they might affect the test result. Tell your child's healthcare provider about all the medicines and supplements your child takes. Ask your child’s provider before stopping any of your child’s regular medicines.
• Talk to your child’s healthcare provider if you have any questions about the test.

How is the test done?

Having this test will take just a few minutes. For young babies, the heel is pricked and a small amount of blood is taken. For older children, a small amount of blood is taken from a vein in your child’s arm with a needle. The blood is collected in tubes and sent to a lab.

Ask your child’s healthcare provider how and when you will get your child’s test results.

What does the test result mean?

Some of the reasons your child’s magnesium level may be higher than normal are:

• Your child has kidney disease
• Your child’s thyroid gland may not be making enough thyroid hormone
• Your child takes a lot of antacid medicine or laxatives that contain magnesium

Some of the reasons your child’s magnesium level may be lower than normal are:

• Your child is not getting the nutrients needed from food
• Your child has inflammatory bowel disease with frequent or long-lasting diarrhea
• Your child has thyroid or parathyroid (gland) disease
• Your child has diabetes that is not well controlled
• Your child has abnormal amounts of calcium or potassium in the blood
• Your child is taking certain medicines such as a diuretic (water pill)

What if my child’s test result is not normal?

Test results are only one part of a larger picture that takes into account your child’s medical history, physical exam, and current health. Sometimes a test needs to be repeated to check the first result. Talk to your child’s healthcare provider about the results and ask questions such as:

• If your child needs more tests
• What kind of treatment your child might need
• What lifestyle, diet, or other changes your child might need to make

If your child’s magnesium level is low, your child’s provider will recommend treatment based on the cause.