Sweat Test

Test Overview

A sweat test, also called a sweat chloride test, measures the amount of chloride in sweat. It is done to help diagnose cystic fibrosis. Normally, sweat on the skin surface contains very little chloride. People with cystic fibrosis have a high level of chloride in their sweat.

During the sweat test, medicine that causes a person to sweat is applied to the skin (usually on the arm or thigh). The sweat is then collected and the amount of chloride in the sweat is measured in a lab.

A sweat test can be done at any age. It may be done as soon as your baby is 10 days old, but it is often done when a baby is 2 to 4 weeks of age. Your child may need more than one sweat test to confirm a diagnosis of cystic fibrosis.