FL - Clinical: Fluoride, Plasma

Test Catalog

Test Name

Test ID: FL    
Fluoride, Plasma

Useful For Suggests clinical disorders or settings where the test may be helpful

Assessing accidental fluoride ingestion


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

Clinical Information Discusses physiology, pathophysiology, and general clinical aspects, as they relate to a laboratory test

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 >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).

Reference Values Describes reference intervals and additional information for interpretation of test results. May include intervals based on age and sex when appropriate. Intervals are Mayo-derived, unless otherwise designated. If an interpretive report is provided, the reference value field will state this.

0.0-4.0 mcmol/L

Interpretation Provides information to assist in interpretation of the test results

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 <1 mcmol/L. Plasma fluoride values >4 mcmol/L indicate excessive exposure and are associated with periostitis.

Cautions Discusses conditions that may cause diagnostic confusion, including improper specimen collection and handling, inappropriate test selection, and interfering substances

In solutions of below pH 5, H(+) complexes with the fluoride ion, thus reducing the free fluoride ion concentration and giving a falsely low reading.


At higher pH (>9), the hydroxyl ion (OH-) will interfere with electrodes, giving a falsely elevated reading.


Specimen must be sent in a plastic vial.

Clinical Reference Provides recommendations for further in-depth reading of a clinical nature

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: Long term use of voriconazole, a fluoride containing medication, is associated with periostitis, fluorosis, and fluoride excess in transplant patients. Clin Infect Dis 2011;52:604-611