Fibroblast Growth Factor 23 (FGF23), Serum/Plasma
Measures FGF23 in blood to help evaluate disorders of phosphate and vitamin D metabolism, especially with low phosphate, bone disease, or unusual calcification.
["FGF23 is a blood marker that helps assess phosphate and vitamin D regulation and should be interpreted with other mineral-metabolism tests."]
Key facts at a glance
- LOINC
- 53431-3
- Short code
- FGF-23 sp6 p chal Plas IA-aCnc
- Synonyms
- FGF-23 sp6 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?
Fibroblast growth factor 23, or FGF23, is a hormone made by bone cells. It helps control blood phosphate and the activity of vitamin D in the kidneys.
Why might I need this test?
This test may be ordered to investigate low blood phosphate, rickets, osteomalacia, or abnormal phosphate loss in the urine. It can also help evaluate inherited disorders that cause excess FGF23 activity.
How is the test performed?
A blood sample is collected and analyzed for FGF23, commonly with an immunoassay. Sample handling and the exact measurement method may vary by laboratory.
How do I prepare for the test?
Fasting is usually not required, but follow the laboratory's instructions. Tell your clinician if you take biotin supplements because some immunoassays can be affected by high biotin levels.
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 FGF23 level may indicate excessive hormone activity, which causes the kidneys to lose phosphate and may contribute to rickets, osteomalacia, or calcium-phosphate deposits. FGF23 can also be elevated in chronic kidney disease. Results must be interpreted with phosphate, vitamin D, kidney function, and other clinical findings because a high or low value alone does not establish a diagnosis.
Short name
Fibroblast Growth Factor 23 (FGF23)
Frequently asked questions
What does FGF23 measure?
What conditions can cause an elevated FGF23 result?
Can an FGF23 test diagnose a condition by itself?
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.
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Medically reviewed by WellAlly Editorial Team Last reviewed August 16, 2026. · Read our editorial policy