Sweat chloride test
Quick answer: A sweat chloride test measures the amount of chloride in sweat collected from the skin. It is the standard test for cystic fibrosis, usually done in children with repeated chest infections, poor growth or a positive newborn screen.
- SampleSweat
- TakesAbout 30 minutes to 1 hour
- Before the testNo special preparation is usually needed; avoid putting creams on the skin where the test will be done.
How the test is done
- 1A small area of skin, usually on the forearm, is cleaned
- 2A medicine that causes sweating is applied, with a mild electrical current to help it soak in
- 3Sweat is collected on a pad or coil for about 30 minutes
- 4The lab measures the chloride in the sweat
What your results can mean
Reading your report
Your doctor will explain whether the result is normal, borderline or suggests cystic fibrosis.
If the result is outside the usual range
A high level can point to cystic fibrosis and usually leads to further tests to confirm. An in-between result may need a repeat test or genetic testing.
Who usually has this test
Babies with a positive newborn screen, and children or adults with repeated chest infections, poor growth or male infertility from absent sperm ducts.
Risks and aftercare
The skin may look red or feel tingly for a few hours; this usually settles on its own.
Names and options
Also called: sweat test, cystic fibrosis test
Listed by the hospital as
- CHLORIDE, SWEAT
Questions about this test
Does the sweat test hurt?
It is not usually painful. You may feel a tingling or warmth where the current is applied, and the skin may look red afterwards.
Can a baby have a sweat test?
Yes, it is commonly done in babies after newborn screening, usually once they are a few weeks old and large enough to make enough sweat.
How is cystic fibrosis linked to male infertility?
Many men with cystic fibrosis or its gene changes are born without the tubes that carry sperm. A sweat test may be part of checking for this.
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This page explains each test in general terms so you know what to expect. It is not medical advice: your doctor decides which tests you need and what your results mean. Reference ranges differ between laboratories. Updated 4 November 2026.