Phosphate in Blood (Phosphorus Test)
Reviewed
Also called: Phosphorus test, P, PO4, Phosphorus-serum, Phosphate, inorganic phosphorus
A phosphate in blood test measures the amount of phosphate in a sample of your blood.
Specimen: Blood
Urgent safety information
Have symptoms of severely low phosphate levels. This condition can become life-threatening and needs immediate treatment. Symptoms may include Muscle pain and/or weakness, Bone pain, Changes in your mental condition, such as feeling confused or very irritable, Seizures, Coma.
Why this test may be ordered
- To help diagnose or monitor kidney disease, especially chronic kidney disease.
- To evaluate bone disorders.
- To assess parathyroid gland function.
- To monitor people with poorly controlled diabetes or acid-base imbalances.
- To follow up on abnormal calcium test results.
Preparation and collection
You may need to fast (not eat or drink) for several hours before you give your blood sample. Certain medicines, vitamins and supplements can affect the accuracy of your test results. So tell your provider about everything you take, including over-the-counter medicines. But don't stop taking any prescription medicines unless your provider tells you to.
A health care professional will take a blood sample from a vein in your arm, using a small needle. This usually takes less than five minutes.
There is very little risk to having a blood test. You may have slight pain or bruising at the spot where the needle was put in, but most symptoms go away quickly.
Understanding results
The meaning of your test results depends on your symptoms, medical history, and the results of other tests.
- Higher than normal (hyperphosphatemia): A higher than normal phosphate level is called hyperphosphatemia. High levels are linked to many conditions, including: Late stages of chronic kidney disease and kidney failure. Limitation: If your phosphate levels are not normal, it doesn't always mean you have a medical condition that needs treatment. Also, children often have higher phosphate levels because their bones are still growing. Next step: If you have questions about your results, talk with your provider.
- Lower than normal (hypophosphatemia): A lower than normal phosphate level is called hypophosphatemia. Limitation: Mildly low levels often aren't a health problem. But many conditions that cause low levels may need treatment. Next step: Your provider may order a phosphate in urine test instead of or with a phosphate in blood test.
- Abnormal levels do not always mean a medical condition needs treatment.
- Children often have higher phosphate levels due to bone growth.
- Results should be interpreted with other tests (calcium, vitamin D, PTH) and medical history.
What to do next
Your provider may order a phosphate in urine test instead of or with a phosphate in blood test. If you have questions about your results, talk with your provider.
- What do my phosphate levels mean in combination with my calcium, vitamin D, and PTH results?
- Do I need any follow-up tests or treatment?
- How can I manage my diet to help balance phosphate levels?
Evidence source
Source: U.S. National Library of Medicine (MedlinePlus). Practices and reference ranges may differ in your country.
U.S. National Library of Medicine: Phosphate in Blood (Phosphorus Test)