Phosphate in Urine
Reviewed
Also called: phosphorous test, P, PO4, inorganic phosphate, PO4 urine concentration
This test measures the amount of phosphate in urine collected over 24 hours. Phosphate contains phosphorus, an electrolyte that helps build bones, make energy, and support nerve and muscle function. The kidneys and intestines control phosphate levels, which are linked to calcium, vitamin D, and parathyroid hormone. The test helps evaluate kidney function, parathyroid disorders, and causes of kidney stones.
Specimen: 24-hour urine sample
Why this test may be ordered
- To understand the cause of high or low phosphate in blood
- To find out if too much phosphate in urine is causing kidney stones
- To diagnose kidney problems
- To diagnose disorders of the parathyroid glands
Preparation and collection
No special preparations needed. Follow all instructions for collecting a 24-hour urine sample.
You will collect all urine over a 24-hour period. Start by urinating in the toilet and noting the time. For the next 24 hours, collect all urine in a special container. Store the container in a refrigerator or cooler with ice. After 24 hours, return the container to your provider or lab as instructed.
There is no known risk to having a phosphate in urine test.
Understanding results
Your results may include guidelines for normal, low, and high levels, but your provider will consider your health, age, and other factors when deciding what is normal for you. To understand what your test results mean, your provider will consider your symptoms, medical history, and the results of other tests. Ask your provider what your results say about your health.
- Normal: Your phosphate level is within the expected range. Your provider will interpret this based on your overall health. Limitation: Normal results do not rule out all conditions. Your provider may consider other tests and your medical history. Next step: Routine
- High: High phosphate levels in urine may indicate kidney disease that affects the kidneys' ability to hold on to phosphate, or hyperparathyroidism (overactive parathyroid gland). However, not all abnormal results mean a medical condition; eating a meal high in phosphorus or using laxatives with sodium phosphate can affect results. Children often have higher levels due to bone growth. Limitation: A high result does not confirm a diagnosis. Your provider will consider other factors and may order additional tests. Next step: Prompt
- Low: Low phosphate levels in urine may indicate kidney disease that affects the kidneys' ability to get rid of extra phosphate, or hypoparathyroidism (underactive parathyroid gland). Limitation: A low result does not confirm a diagnosis. Your provider will consider other factors and may order additional tests. Next step: Prompt
- Results are interpreted by your healthcare provider based on your overall health, symptoms, and other test results.
- Abnormal levels do not always mean a medical condition that needs treatment.
- Diet (high-phosphorus meal) and medications (laxatives with sodium phosphate) can affect results.
- Children often have higher phosphate levels because their bones are still growing.
What to do next
If your results are not normal, talk with your provider to understand what they mean for your health. Your provider may recommend additional tests, such as a blood phosphate test, to get a complete picture.
- What do my phosphate levels mean for my kidney and parathyroid health?
- Do I need any follow-up tests?
- How do my diet and medications affect my phosphate levels?