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Fluoride/Creatinine Ratio, Urine

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

Measures urine fluoride relative to creatinine to help evaluate fluoride exposure while accounting for differences in urine concentration.

Quick summary

["An elevated result may indicate increased fluoride exposure or intake, but interpretation depends on the patient’s age, sources of exposure, and collection timing."]

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

Key facts at a glance

LOINC
56656-2
Short code
Fluoride/Creat Ur-Rto
Synonyms
Fluoride/Creat Ur-Rto
Category
kidney
Sample
urine
Container
Sterile urine container
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Specimen volume
10 mL
Stability
Room temperature: 2h, Refrigerated: 24h, Frozen: 7d
Hemolysis max
0
Lipemia max
0
Icterus max
0
TAT
4–24 hours
Order
routine

What is this test?

This urine test measures the amount of fluoride in the urine compared with the amount of creatinine. Creatinine is used as a reference to help account for how concentrated or dilute the urine sample is.

Why might I need this test?

It may be used to assess fluoride exposure from drinking water, supplements, toothpaste, occupational sources, or other environmental sources. A clinician may order it when excess exposure is suspected or when monitoring a patient at risk of fluoride-related effects.

How is the test performed?

A urine specimen is collected and tested in the laboratory. The fluoride result is compared with the urine creatinine result to calculate the fluoride/creatinine ratio. Follow the collection instructions provided by the healthcare professional.

How do I prepare for the test?

Fasting is generally not required for a urine fluoride/creatinine ratio, but collection timing and recent fluoride exposure can affect the result. Tell your clinician about fluoride supplements, fluoride-containing toothpaste or mouthwash, and any water-fluoride concerns. If a 24-hour collection is requested, collect urine for the full period as directed.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

Urine Fluoride/Creatinine Ratio

Frequently asked questions

Does this test measure the fluoride in my drinking water?
No. It measures fluoride eliminated in urine, which can reflect fluoride absorbed from water and other sources. The result alone cannot determine where the exposure came from.
Why is creatinine included in the result?
Urine concentration varies with fluid intake and hydration. Comparing fluoride with creatinine helps reduce the effect of urine dilution or concentration on the reported ratio.
Can toothpaste or supplements affect the result?
Yes. Swallowed fluoride from toothpaste, mouth rinse, or supplements can temporarily increase urine fluoride, so recent use and collection timing should be discussed with the clinician.
  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