Health Library
Cystic Fibrosis in Children

What is Cystic Fibrosis?

Cystic fibrosis is a lifelong disease that affects the respiratory, endocrine, reproductive and digestive systems. About 35,000 children and adults in the United States have CF. This disease is caused by a defective gene that makes the body produce very thick, sticky mucus. This mucus:
  • Clogs the lungs and leads to lung infections
  • Blocks the pancreas and prevents normal breakdown and use of food by the body, as well as inhibits the body’s ability to produce insulin
  • Affects bowel function, leading to constipation or loose stools, due to the increased mucus in the intestines
  • Clogs a part of the male reproductive system (vas deferens), or the vas deferens is absent altogether, making most males with CF sterile

Cystic Fibrosis Symptoms

People with CF can have a variety of symptoms, including:

  • Salty-tasting skin
  • Daily cough, at times with mucus
  • Lung infections
  • Shortness of breath
  • Poor growth or slow weight gain even with a good appetite
  • Frequent greasy, bulky, foul-smelling stools or trouble having a bowel movement

Cystic Fibrosis Causes

  • Cystic fibrosis is a genetic disease. This means that people inherit it from their parents through genes (or DNA). 
  • To have cystic fibrosis, a person must inherit two copies of the defective CF gene, getting one copy from each parent. Carriers are not affected.

Recessive inheritance of CF.

© 2011 CF Foundation
Printed with permission from the Cystic Fibrosis Foundation

Cystic Fibrosis Diagnosis

Most people are diagnosed with CF at birth with newborn screening, or before 2 years of age. A doctor who sees the symptoms of CF will order a sweat test or a genetic test to confirm the diagnosis.

A sweat test is the most common test used to diagnose CF. It is a painless test. A small electrode (disk) is placed on the skin (usually on the arm) to get the sweat glands to make sweat. The sweat is collected, and the amount of chloride (a part of salt) is measured. An elevated level of chloride means that the person has cystic fibros 


Children less than
6 months old 
Less than 30 mmol/L  Between 30-59 mmol/L  60 mmol/L or higher 
Children over
6 months old 
Less than 40 mmol/L
Between 40-59 mmol/L  60 mmol/L or higher 


  • Mmol/L is a measure of concentration. The new range for all ages is less than 30 is normal and 30-59 is borderline, 60 and above is high.
  • Borderline chloride levels are reviewed on a case-by-case basis.

The best place to get a sweat test done is at a Cystic Fibrosis Foundation-accredited care center.

How Do You Treat Cystic Fibrosis?

Because the severity of CF differs from person to person, and CF lung infections flare up from time to time, there is no “typical” day. However, each day most people with CF:

  • Take pancreatic enzyme supplement capsules with every meal and most snacks to help digest fat and protein. Even babies who are breastfeeding may need to take enzymes.
  • Take multi-vitamins, especially the fat-soluble vitamins A, D, E and K.
  • Make sure they get plenty of salt by adding salt to food or eating salty snacks.
  • Eat a high-calorie, high-protein diet.
  • Clear the lungs at least twice and sometimes up to four or more times a day. This is done using techniques called “Airway Clearance.” In infants, it is done by clapping on the chest in a certain way. In toddlers, children, and adults, it is done using a variety of approaches, such as a therapy vest that shakes the chest wall. This helps move the thick mucus out of the lungs and lessens the chance of lung infection.
  • Take liquid medicines that are made into a mist or aerosol and then inhaled through a nebulizer (called aerosolized medicines). There are several types of aerosolized medicines with different actions including thinning the mucus, opening the airways, and fighting infection.

Each child’s doctor will decide which, if any, of these medicines and treatments are needed.

Last Updated 10/2023

Reviewed By Jayne Massengale, RN, MSN, CPN