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Sweat chloride test

Also called: Sweat test, Cystic fibrosis test

The sweat test measures salt in sweat. It's the main test to diagnose cystic fibrosis.

SampleSweat
Fasting?Usually not needed
ResultsSame day to a few days
Good to knowOne result rarely tells the whole story. Your provider looks at your results together with your symptoms, exam, and other tests.

What the test is

It's often done after a positive newborn screen.

Why it's done

  • Positive newborn screen for CF
  • Frequent lung infections, poor growth, or salty-tasting skin

Getting ready and what happens

  • No preparation is needed.

How the test is done

  • A painless medicine and mild current on the arm make it sweat; the sweat is collected for 30 minutes.

What the results mean

ResultTypical range for adults
Unlikely CF29 mmol/L or less
Intermediate30 to 59 mmol/L
Likely CF60 mmol/L or more

Normal ranges vary from lab to lab and can differ by age, sex, and pregnancy. Your report lists your lab's own range next to each result. A result a little outside the range is often not a problem.

High

Supports cystic fibrosis; genetic testing and a CF specialist follow.

Questions to ask your provider

  • What do my results mean for me?
  • Do I need to repeat this test or have other tests?

Related conditions

Related tests

Sources

Last updated 2026-11-13.