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Fibroblast Growth Factor 23 (FGF23), Plasma — Analyte Concentration

Published: August 9, 2026Updated: August 16, 2026

Measures FGF23, a hormone that helps regulate blood phosphate and active vitamin D. It may be used to evaluate disorders of mineral and bone metabolism.

Quick summary

["FGF23 helps control phosphate and vitamin D levels, so the result is interpreted with calcium, phosphate, vitamin D, and kidney function tests."]

Medically reviewed by WellAlly Editorial TeamLast reviewed August 16, 2026Editorial policy

Key facts at a glance

LOINC
53425-5
Short code
FGF-23 pre chal Plas IA-aCnc
Synonyms
FGF-23 pre 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, in plasma. FGF23 is made mainly by bone and acts on the kidneys to regulate phosphate and vitamin D.

Why might I need this test?

A clinician may order this test when phosphate, calcium, or vitamin D results are abnormal, particularly with low phosphate, kidney disease, or a suspected disorder of bone or mineral metabolism. It may also help evaluate certain tumors or inherited conditions that affect phosphate.

How is the test performed?

A blood sample is drawn into a tube, and the plasma portion is measured using a laboratory method. The result is usually reported as a concentration of FGF23.

How do I prepare for the test?

Fasting is usually not required, but follow the instructions provided by the laboratory or ordering clinician. Do not stop medicines or supplements unless your clinician specifically advises you to do so.

Reference range

Adult: 44-147 U/LN/A

Specimen: plasma

No special preparation required. Avoid fatty meals before the test if possible.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

FGF23

Frequently asked questions

Is FGF23 the same as a phosphate test?
No. FGF23 is a hormone that helps regulate phosphate, while a phosphate test directly measures the amount of phosphate in the blood.
Do I need to fast for this test?
Fasting is usually not necessary. Follow any specific instructions from the ordering clinician or laboratory.
Does one abnormal FGF23 result diagnose a condition?
No. An abnormal result must be considered with calcium, phosphate, vitamin D, kidney function, symptoms, and other findings.
  1. 1
    MedlinePlus — Laboratory TestsSource
  2. 2
    Lab Tests OnlineSource
  3. 3
    Mayo Clinic — Tests & ProceduresSource

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.

Medical Disclaimer

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