Fibroblast Growth Factor 23 (FGF23), Serum/Plasma
Measures FGF23, a hormone that helps regulate phosphate and vitamin D. It may help evaluate disorders affecting phosphate handling and bone mineralization.
["An FGF23 blood test helps assess phosphate regulation and may support evaluation of certain bone and kidney disorders."]
Key facts at a glance
- LOINC
- 53426-3
- Short code
- FGF-23 sp1 p chal Plas IA-aCnc
- Synonyms
- FGF-23 sp1 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 how the kidneys handle phosphate and influences vitamin D and bone mineralization.
Why might I need this test?
Your doctor may order this test when phosphate levels are abnormal or when there is concern about a condition that causes phosphate wasting, such as certain inherited kidney or bone disorders. It may also be used when evaluating vitamin D-related or tumor-associated hormone abnormalities.
How is the test performed?
A blood sample is collected, usually from a vein in your arm. The laboratory measures the amount of FGF23 in serum or plasma using a validated laboratory method.
How do I prepare for the test?
Fasting is generally not required for this test, but follow your doctor's or laboratory's instructions. Tell the healthcare team about medicines or supplements that affect phosphate or vitamin D, because they may affect the 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.
An elevated FGF23 level may indicate that the body is trying to reduce phosphate levels by increasing phosphate loss through the kidneys. This can occur with certain inherited disorders, vitamin D abnormalities, or FGF23-producing tumors. A low level may occur in some situations that suppress FGF23 activity, but results must be interpreted with phosphate, kidney function, vitamin D, and other laboratory findings.
Short name
FGF23
Frequently asked questions
Does the FGF23 test require fasting?
What does an abnormal FGF23 result mean?
Is FGF23 the same as a phosphate 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