Fibroblast Growth Factor 23 (FGF-23), Serum/Plasma — Concentration
Measures FGF-23, a hormone made by bone cells that helps regulate blood phosphate and active vitamin D.
["This blood test helps evaluate disorders that affect blood phosphate, vitamin D, and bone or kidney function."]
Key facts at a glance
- LOINC
- 53430-5
- Short code
- FGF-23 sp5 p chal Plas IA-aCnc
- Synonyms
- FGF-23 sp5 p chal Plas IA-aCnc
- Category
- liver
- Sample
- plasma
- Container
- Lavender-top (EDTA) or Green-top (Heparin)
- Units
- N/A
- Ref low
- 44
- Ref high
- 147
- Fasting
- false
- Population
- adult
- Sex
- all
- Age range
- 18–65 years
- Method
- ia
- CPT
- 84075
- SNOMED
- 27550007
- Specimen volume
- 5 mL
- Stability
- Room temperature: 4h, Refrigerated: 24h, Frozen: 7d
- Hemolysis max
- 500
- Lipemia max
- 1000
- Icterus max
- 500
- TAT
- 4–24 hours
- Order
- routine
What is this test?
This test measures the concentration of fibroblast growth factor 23 (FGF-23) in blood. FGF-23 is produced mainly by bone cells and helps control how the kidneys handle phosphate and active vitamin D.
Why might I need this test?
A clinician may order this test when phosphate levels are unexpectedly high or low, or when evaluating kidney disease, bone abnormalities, vitamin D problems, or a condition that causes excessive calcification.
How is the test performed?
A blood sample is collected, usually from a vein, and the FGF-23 level is measured in the laboratory. The result is often interpreted together with phosphate, calcium, kidney function, parathyroid hormone, and vitamin D tests.
How do I prepare for the test?
Special preparation is usually not required for a routine FGF-23 blood test. Follow any instructions provided by your healthcare professional, particularly if this test is being repeated during treatment.
Reference range
Adult: 44-147 U/LN/A
No special preparation required. Avoid fatty meals before the test if possible.
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
An elevated FGF-23 level may occur with reduced kidney function or conditions that cause the body to lose too much phosphate and suppress active vitamin D. A lower level may be seen in some disorders that cause phosphate to be retained. FGF-23 should not be interpreted by itself because kidney function, phosphate, vitamin D, and parathyroid hormone can affect its meaning.
Short name
FGF-23
Frequently asked questions
Is the FGF-23 test the same as a standard vitamin D test?
Does an abnormal FGF-23 result diagnose a specific condition?
Does the test require an overnight fast?
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 16, 2026. · Read our editorial policy