Phosphorus (phosphate) test
Quick answer: A phosphorus test measures phosphate, a mineral that works with calcium to build bones and teeth, in your blood or urine. It is ordered with calcium for bone, kidney and parathyroid problems, and for kidney stones.
- SampleBlood or 24-hour urine
- TakesAbout 5 minutes for blood; 24 hours for urine
- Before the testNo special preparation is usually needed for blood; for the 24-hour urine test, you will be given a container and collection instructions.
How the test is done
- 1For blood, the skin is cleaned and a needle draws a sample
- 2A fasting sample is sometimes preferred
- 3For 24-hour urine, you collect all urine over a full day
- 4The sample goes to the lab, often with calcium tested too
What your results can mean
Reading your report
Normal ranges differ between labs, so compare your result with the range printed on your report and discuss it with your doctor.
If the result is outside the usual range
A high level can be seen with kidney disease, an underactive parathyroid gland or too much vitamin D. A low level can be seen with an overactive parathyroid gland, poor diet, vitamin D deficiency, alcohol use or some medicines.
Who usually has this test
People with bone, kidney or parathyroid problems, kidney stones, or abnormal calcium results.
Risks and aftercare
A blood draw may leave a small bruise, and urine collection has no risks.
Names and options
Also called: serum phosphorus, phosphate test, urine phosphorus
Options
- Serum
- 24-hour urine
Listed by the hospital as
- PHOSPHOROUS, SERUM
- PHOSPHORUS 24 HRS URINE
Questions about this test
Why are phosphorus and calcium tested together?
Calcium and phosphorus are controlled together by parathyroid hormone and vitamin D. Looking at both helps doctors find the cause when one is abnormal.
Why is phosphorus high in kidney disease?
Healthy kidneys remove extra phosphorus from the body. When kidneys are not working well, it builds up, which can affect bones and blood vessels over time.
Can food affect a phosphorus test?
Yes. A recent meal can change the level slightly, so some labs prefer a fasting sample. Follow the instructions you are given.
Related tests
Tamara Hospital & IVF Centre, Rajajinagar
34/3, 10th Cross Road, opp. Vardhaka Sardar Patel School, 1st N Block, 2nd Stage, Rajajinagar, Bengaluru 560010
The hospital is open 24 hours. Call before you come to check the timing for your scan or sample collection.
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This page explains each test in general terms so you know what to expect. It is not medical advice: your doctor decides which tests you need and what your results mean. Reference ranges differ between laboratories. Updated 4 November 2026.