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Sweat Test

What To Think About

  • Your child may need more than one sweat test to confirm a diagnosis of cystic fibrosis.
  • A sweat test can't identify carriers of the cystic fibrosis gene. If your child is diagnosed with cystic fibrosis, you may wish to talk with your doctor about genetic counseling. To learn more, see the topic Cystic Fibrosis Carrier Screening.
  • Adults generally have higher salt concentrations in their sweat than children. Also, sweat test results in adults can vary widely. This is especially true in women, because the amount of salt in their sweat can vary with the phase of their menstrual cycle. Enough sweat must be collected to get accurate test results.
  • If results of a sweat test are positive or unclear (especially in babies), a blood test may be done to detect changes in the genetic material (DNA) that causes cystic fibrosis. Blood test results are usually ready in 10 to 21 days. To learn more, see the topic Genetic Test.
  • Sweat tests should be done at labs that are certified by the Cystic Fibrosis Foundation ( These labs perform a large number of sweat tests and are skilled at sweat test techniques and interpretation.


  1. Farrell PM, et al. (2008). Guidelines for diagnosis of cystic fibrosis in newborns through older adults: Cystic Fibrosis Foundation consensus report. Journal of Pediatrics, 153(2): S4–S14.

Other Works Consulted

  • Chernecky CC, Berger BJ (2013). Laboratory Tests and Diagnostic Procedures, 6th ed. St. Louis: Saunders.

  • Fischbach FT, Dunning MB III, eds. (2009). Manual of Laboratory and Diagnostic Tests, 8th ed. Philadelphia: Lippincott Williams and Wilkins.

  • LeGrys VA, et al. (2007). Diagnostic sweat testing: The Cystic Fibrosis Foundation Guidelines. Journal of Pediatrics, 151(1): 85–89.

  • Pagana KD, Pagana TJ (2010). Mosby’s Manual of Diagnostic and Laboratory Tests, 4th ed. St. Louis: Mosby.

ByHealthwise Staff
Primary Medical ReviewerJohn Pope, MD - Pediatrics
Specialist Medical ReviewerSusanna McColley, MD - Pediatric Pulmonology
Current as ofJuly 18, 2013

WebMD Medical Reference from Healthwise

Last Updated: July 18, 2013
This information is not intended to replace the advice of a doctor. Healthwise disclaims any liability for the decisions you make based on this information.

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