Fibroblast Growth Factor 23 (FGF23) Concentration, Serum/Plasma
Measures FGF23, a hormone that regulates phosphate and vitamin D, to help evaluate conditions that may cause low phosphate or impaired bone mineralization.
["An elevated FGF23 level may help explain low phosphate and bone or mineral abnormalities."]
Key facts at a glance
- LOINC
- 53428-9
- Short code
- FGF-23 sp3 p chal Plas IA-aCnc
- Synonyms
- FGF-23 sp3 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 blood test measures fibroblast growth factor 23, or FGF23. FGF23 helps control phosphate levels and vitamin D activation in the kidneys.
Why might I need this test?
Your clinician may order this test when phosphate levels are low, bone pain or weakness is present, or imaging suggests a disorder of mineral metabolism. Results are usually considered with phosphate, calcium, kidney function, vitamin D, and other tests.
How is the test performed?
A blood sample is collected, usually from a vein, and the FGF23 level is measured using a laboratory assay. The specimen may be serum or plasma, depending on the test used.
How do I prepare for the test?
Fasting is generally not required for this test, but follow your clinician's or laboratory's instructions. Tell the laboratory if you are taking biotin supplements, because high doses may affect some immunoassay results.
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.
A high FGF23 level can cause the kidneys to reduce phosphate retention and limit active vitamin D production, potentially leading to low phosphate and weakened or painful bones. Possible causes include rare phosphate-wasting genetic disorders and, in adults, FGF23-producing tumors. A low or normal result does not identify one specific condition and must be interpreted with the other laboratory findings.
Short name
FGF23 blood test
Frequently asked questions
Is the FGF23 test the same as a phosphate test?
Does an abnormal FGF23 result confirm a diagnosis?
Does biotin supplementation affect the test?
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