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Test ID: FL Fluoride, Plasma

Reporting Name

Fluoride, P

Useful For

Assessing accidental fluoride ingestion


Monitoring patients receiving sodium fluoride for bone disease or patients receiving voriconazole therapy

Clinical Information

Fluoride induces bone formation by stimulating osteoblasts. Because fluorides increase bone density, they are used in dental preparations and as an antiosteoporotic agent. However, prolonged high exposure to fluoride produces changes in bone morphology consistent with osteomalacia, including prolonged mineralization lag time and increased osteoid thickness. The adverse skeletal effects of fluoride are associated with plasma fluoride greater than 4 mcmol/L. Chronic fluorosis may produce osteosclerosis, periostitis, calcification of ligaments and tendons, and crippling deformities.


Prolonged exposure to the fluoride-containing antifungal agent voriconazole can produce high plasma fluoride concentrations and bone changes (periostitis). Several other medicines also contain fluoride are used for treating skin diseases (eg, flucytosine, an antifungal) and some cancers (eg, fluorouracil, an antimetabolite).


Humans exposed to fluoride-treated water typically have plasma fluoride in the range of 1 to 4 mcmol/L. Those who are not drinking fluoride-treated water have plasma fluoride less than 1 mcmol/L. Plasma fluoride values greater than 4 mcmol/L indicate excessive exposure and are associated with periostitis.

Report Available

2 to 8 days

Day(s) Performed


Clinical Reference

1. Cardos VES, Whitford GH, Aoyama H, et al: Daily variations in human plasma fluoride concentrations. J Fluorine Chem. 2008:129;1193-1198

2. Wermers RA, Cooper K, Razonable RR, et al: Fluoride excess and periostitis in transplant patients receiving long-term voriconazole therapy. Clin Infect Dis. 2011 Mar 1;52(5):604-611

3. Rifai N, Horvath AR, Wittwer CT, eds: Tietz Textbook of Clinical Chemistry and Molecular Diagnostics. 6th ed. Elsevier; 2018

4. Agency for Toxic Substances and Disease Registry: Toxicological profile for fluorides, hydrogen fluoride, and fluorine. US Department of Health and Human Services 2003. Accessed March 2020. Available at

Method Name

Ion-Selective Electrode (ISE)

Specimen Type

Plasma Heparin

Specimen Required

Collection Container/Tube: Green top (sodium heparin)

Submission Container/Tube: Plastic vial

Specimen Volume: 3 mL

Collection Instructions: Centrifuge and aliquot plasma into a plastic vial. Glass tubes are not acceptable.

Specimen Minimum Volume

1.2 mL

Specimen Stability Information

Specimen Type Temperature Time Special Container
Plasma Heparin Refrigerated (preferred) 14 days
  Ambient  14 days
  Frozen  14 days

Reference Values

<4.1 mcmol/L

Test Classification

This test was developed, and its performance characteristics determined by Mayo Clinic in a manner consistent with CLIA requirements. This test has not been cleared or approved by the US Food and Drug Administration.

CPT Code Information


LOINC Code Information

Test ID Test Order Name Order LOINC Value
FL Fluoride, P 14726-4


Result ID Test Result Name Result LOINC Value
8641 Fluoride, P 14726-4
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