Phosphorus Test

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KEY POINTS

• This test measures the amount of phosphorus in blood. Phosphorus is a chemical your body needs to get energy from the food you eat. It’s also important for healthy bones.
• The test is done to help diagnose certain medical problems, or to see how well treatment for a disease is working.
• Talk to your child’s healthcare provider about what the test results mean and ask any questions you have.

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What is the phosphorus test?

This test measures the amount of phosphorus in blood. Phosphorus is a mineral your child’s body needs to build strong teeth and bones. It’s also important for healthy nerves and muscles.

Phosphorus is also called phosphate. Your child can get phosphate from food.

Why is this test done?

This test may help diagnose and treat a medical problem you are having. It does not diagnose a specific problem but it can help your healthcare provider know what other tests you might need. It’s also a way to see how well treatment for a disease is working. For example, it may be done to:

• Help diagnose kidney failure or to see how well dialysis is working when you have kidney failure
• During treatment for diabetic ketoacidosis (a dangerous buildup of acids in the blood from a lack of insulin)
• To help your child’s healthcare provider understand the cause of a low or high calcium level

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. Make sure your child’s healthcare provider knows about any medicines, herbs, or supplements that your child is taking. Ask your 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. 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 healthcare provider when and how you will get the result of the test. A phosphorus level may also be measured from a urine sample.

What does the test result mean?

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

• Your child has kidney disease.
• Your child’s body is not making enough parathyroid hormone.
• Your child is having chemotherapy.
• Your child has a muscle injury.
• Your child has a severe infection.
• Your child has been taking phosphorus supplement, or your child is getting too much phosphorus in their diet.

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

• Your child’s body is making too little thyroid hormone or too much parathyroid hormone.
• Your child has been taking antacids for a long time.
• Your child’s calcium level is high.
• Your child is unable to eat or absorb food.
• Your child has kidney disease.
• Your child has been severely burned.

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