Phosphorus (Serum)
This test measures the amount of phosphorus, a mineral essential for healthy bones and cells, in your blood serum.
["Your blood phosphorus levels help doctors assess bone health and metabolic function."]
Key facts at a glance
- LOINC
- 17447-4
- Short code
- Phosphate Stl Ql
- Synonyms
- Phosphate Stl Ql
- Category
- electrolyte
- Sample
- stool
- Container
- Clean container
- Units
- N/A
- Ref low
- 2.5
- Ref high
- 4.5
- Critical range
- 1 N/A – —
- Fasting
- false
- Population
- adult
- Sex
- all
- Age range
- 18–65 years
- CPT
- 84100
- Specimen volume
- 5 g
- Stability
- Refrigerated: 24h, Frozen: 7d
- TAT
- 4–24 hours
- Order
- routine
Why Is This Test Done?
Doctors may order a serum phosphorus test to check for conditions affecting bone metabolism, kidney function, or hormonal balance. It’s often used alongside other blood tests to diagnose or monitor diseases like kidney disease, diabetes, or metabolic bone disorders.
What to Expect Before the Test
No special preparation is needed. You may have a small needle inserted into your arm to draw blood, which usually takes a few minutes. If you’re on a blood thinner, let your doctor know before the test.
What the Results Mean
Phosphorus levels can vary based on diet, kidney function, and health conditions. While reference ranges differ by lab, very high or very low levels may signal underlying issues like kidney disease, vitamin D deficiency, or metabolic disorders.
Common Conditions Monitored
This test helps diagnose or track conditions like chronic kidney disease, hyperparathyroidism, or conditions affecting calcium and phosphorus balance, such as hypoparathyroidism or certain cancers.
Reference range
Adult: 2.5-4.5 mg/dLN/A
No special preparation usually required. Stay well hydrated. Inform your healthcare provider of all medications and supplements you are taking.
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
Abnormal phosphorus levels can indicate problems with bone formation, mineral metabolism, or organ function. High levels may suggest kidney issues or overuse of certain medications, while low levels could point to malnutrition, hormonal imbalances, or kidney disorders.
Short name
Serum Phosphorus
Frequently asked questions
What causes abnormal phosphorus levels in blood?
How long does it take to get results?
Can diet affect phosphorus test results?
Sources
- 1
- 2Lab Tests OnlineSource
- 3
Click any link to access the full source. PubMed Central (PMC) links provide free full-text access.
This information is for educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment.
This content is for general informational and educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always seek the guidance of a qualified healthcare provider with any questions you have about a medical condition, and never disregard professional medical advice or delay seeking it because of something you read here.
If you think you may have a medical emergency, call your local emergency number or go to the nearest emergency department immediately.
Medically reviewed by WellAlly Editorial Team Last reviewed August 17, 2026. · Read our editorial policy