Phosphorus (Serum) Concentration
This test measures the amount of phosphorus, an essential mineral, in your blood serum. Phosphorus helps maintain healthy bones and teeth and supports normal cell function.
["Phosphorus levels can indicate bone health, kidney function, or metabolic balance."]
Key facts at a glance
- LOINC
- 13542-6
- Short code
- Phosphate CSF-mCnc
- Synonyms
- Phosphate CSF-mCnc
- Category
- electrolyte
- Sample
- csf
- Container
- Sterile tube
- 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
- 1-2 mL
- Stability
- Immediate analysis required, Refrigerated: 1h
- Hemolysis max
- 200
- TAT
- 4–24 hours
- Order
- routine
Why Is This Test Done?
Your healthcare provider may order this test to check for conditions affecting phosphorus metabolism, such as kidney disease, bone disorders, or metabolic disorders. It may also be used to monitor treatment for conditions like hypercalcemia or hypocalcemia.
What to Expect Before the Test
No special preparation is usually needed. You may be asked to fast for 8–12 hours before the test if it involves a blood draw, but this is not always required for phosphorus testing alone. Bring any medications you’re currently taking to your appointment.
What Happens During the Test?
A healthcare professional will draw blood from a vein in your arm. The blood sample will be sent to a lab for analysis. The test typically takes a few minutes, and you may feel a slight pinch during the draw.
What Are Possible Results?
Results are reported as a mass concentration (typically in milligrams per deciliter, mg/dL). Your results will be compared to standard reference ranges provided by your lab, though exact values may vary by facility.
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.
Low phosphorus levels (hypophosphatemia) may cause muscle weakness, bone pain, or abnormal heart rhythms. High phosphorus levels (hyperphosphatemia) can contribute to soft tissue calcification, kidney issues, or metabolic disturbances. Chronic kidney disease is the most common cause of abnormal phosphorus levels.
Short name
Serum Phosphorus
Frequently asked questions
What causes low phosphorus levels?
What causes high phosphorus levels?
How is phosphorus tested?
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