Phosphorus Level Blood Test

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The phosphorus level blood test is performed to determine how much phosphorus is in a patient’s blood. Phosphorus is necessary for healthy nerve and muscle function, healthy teeth and bones, and to process the body’s energy. Having phosphorus levels that are too high or too low could indicate several different medical conditions.

Why is this Test Done?

This test may be done to help monitor or diagnose a variety of medical conditions. Such conditions may include:

  • Nutritional disorders
  • Bone problems
  • Kidney disorders
  • Gastrointestinal disorders
  • Calcium problems

Preparation and Procedure

Most patients will not have to prepare for a phosphorus level blood test. However, drugs such as antacids, diuretics, and laxatives may alter the patient’s test results. Patients taking these types of medications may have to decrease their dose or temporarily discontinue they for a certain period of time before the test. The patient’s doctor will determine if this is necessary and/or safe for the individual patient.

To test phosphorus levels, a blood sample is necessary. Babies often have their blood sample obtained through using a lancet to puncture the skin and then allowing blood to collect in a vial. Older children and adults will have venipuncture. A health care provider will carefully insert a needle into a vein and allow blood to collect into a tube. The puncture site may be bruised and sore after this test. Overall, venipuncture and using a lancet is not painful, but the patient may experience slight discomfort as the needle is inserted. In some cases, a time urine sample may be used. If a timed urine sample is required, the patient’s doctor will instruct them on how to provide their sample.


If the patient’s phosphorus levels are low, also referred to as hypophosphatemia, it can indicate several different medical conditions, such as:

  • Hypercalcemia, especially because of hyperparathyroidism
  • Malnutrition
  • Severe burns
  • Hypothyroidism
  • Chronic antacid use
  • Overuse of diuretics
  • Alcoholism
  • Diabetic ketoacidosis post treatment
  • Hypokalemia
  • Osteomalacia and rickets because of vitamin D deficiencies

If the patient’s phosphorus levels are high, also referred to as hypophosphatemia, it can indicate several different medical conditions, such as :

  • Kidney failure
  • Diabetic ketoacidosis (initially)
  • Hypoparathyroidism
  • Increasing dietary intake of phosphates due to phosphate supplementation

If phosphate levels are abnormally high it may lead to calcification-related organ damage due to calcium phosphate deposits in the tissues. Urine and blood phosphate levels may be affected by using laxatives and enemas that contain sodium phosphate, intravenous glucose administration, and using dietary vitamin D supplements excessively. Pre-packaged foods and soft drinks are also quite high in phosphorus so consuming these regularly may result in high phosphate levels in the body.


WebMD. (2009). Phosphate in Blood. Retrieved on October 15, 2010 from WebMD:

Lab Tests Online. (2010). Phosphorus. Retrieved on October 15, 2010 from Lab Tests Online: