FGF23 Gene Mutation Analysis, Blood

About the Test

The FGF23 gene provides instructions for making fibroblast growth factor 23, a hormone that helps regulate phosphate and vitamin D levels. This test examines the gene for variants (mutations) that may alter how the hormone is produced or functions. It is typically ordered when a clinician suspects an inherited disorder of phosphate metabolism.

Why It May Be Ordered

Your healthcare provider may order this test if you have unexplained low or high phosphate levels, abnormal vitamin D levels, bone abnormalities, or a family history of conditions affecting mineral metabolism. It can help distinguish inherited genetic causes from other reasons for these findings.

How the Test Is Done

A blood sample is collected, usually from a vein in your arm, and sent to a specialized laboratory. The laboratory extracts DNA and analyzes the FGF23 gene for sequence changes. Results are generally reported as the specific gene variant identified, if any, along with an interpretation.

What Results Mean

A positive result indicates that a genetic variant was found in the FGF23 gene, which may help explain your symptoms and can inform family screening and management. A negative result lowers but does not entirely rule out a genetic cause, depending on the testing method used. Results should always be interpreted by your healthcare provider in the context of your clinical picture.