Sweat Chloride Testing for Cystic Fibrosis (CF)

If you or your child has been suspected of having cystic fibrosis (CF), your doctor might recommend a sweat test to confirm a diagnosis.

The sweat chloride test is the gold standard for the diagnosis of CF. The amount of chloride in a person's sweat will indicate whether someone is likely to have CF. A doctor's order is required to have testing, and it might be recommended based on factors such as neonatal screening, family history or symptoms consistent with CF.

See below for the procedure for sweat chloride testing at MU Health Care.

Test Preparation

  • The test should not be conducted if a patient is taking mineralocorticoids. Please consult with your doctor about stopping your medication before testing. Do not stop taking a prescribed medicine without talking with your doctor first.
  • The patient should be feeling well on the day of testing. If you or your child has a cold or fever, please contact your doctor to re-schedule testing.
  • The patient must be hydrated. A couple days before your test, please be sure to drink plenty of water.
    • For infants: make certain that bottles are finished as usual
    • Breastfed infants: mom can increase her water intake and feed like normal
    • Children and adults: Please drink plenty of water and avoid drinks containing a lot of sugar or caffeine.
  • Patient should not use any lotions on their arms or legs within 24 hours of testing.
    • This includes hydrocortisone cream, moisturizer and sunscreen.
  • Patient should dress warmly by wearing a jacket/coat or blanket on the day of testing. Keep in mind that testing will require access to the arms and/or thighs.
  • Arrive 15 minutes before your appointment time. Please call 573-884-4522 if you are unable to make your appointment or if you are running late.
  • Patients who are late by more than 15 minutes with no notice will be required to reschedule.

Sweat Collection Procedure

  • Patient or guardian will need to sign a consent for testing.
  • Typically, testing takes 90 minutes, but it might take up to three hours.
  • Patient's arms and/or thighs will be cleaned with alcohol and water.
  • A cold, wet gel disc will be placed on the cleaned testing site. The area will be stimulated by an electrical current for 5 minutes.
  • Patient's arm/thigh will be cleaned again with water and then dried.
  • A collection device will be fastened to the area to collect the sweat.
  • Patient will be wrapped in a blanket and kept warm during collection for about 30 minutes
    • Patient may eat, drink/nurse during this time. If wanted, you may bring small toys or tablets for entertainment during the collection time.
  • After sweat is collected, the device will be removed, and the patient's arm/thigh will be cleaned again.
  • Testing is repeated on a different arm/thigh.

Potential Adverse Reactions

  • The test is very safe, and the risk of harm is small.
  • The procedure might produce a tingling, itchy or scratchy sensation.
  • The area that was stimulated might remain red for a few hours after the test.
  • Rarely, the stimulated area might blister.
  • Burns are very rare but can happen.


  • Results will be given to your doctor within 24 hours of testing

Please contact your doctor or the Women’s and Children's Hospital Lab at 573-884-4522 with any questions or concerns.