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Cystic fibrosis

How is cystic fibrosis inherited?

Cystic fibrosis is an inherited condition. On this page, find out how cystic fibrosis is passed on. 

Cystic fibrosis (CF) is an inherited condition caused by a faulty gene. People with CF are born with the condition. You cannot catch CF because it’s not contagious.

People with CF have a problem with the gene that contains the instructions for a protein that helps to control the movement of salt and water in and out of the cells. This gene is called CFTR. 

Everyone has two CFTR genes, one from each parent. People with CF have two faulty CFTR genes – one faulty gene inherited from the biological mother and one faulty gene from the biological father.  

Most of the time, parents don’t have CF themselves but are carriers. This means they have one faulty CFTR gene and one normal CFTR gene. Carriers usually have no symptoms. About 1 in 25 of us carries the faulty CFTR gene, usually without knowing it.

If both biological parents are carriers, there is a: 

  • 1 in 4 chance their child will have CF 
  • 1 in 2 chance their child will be a carrier of CF 
  • 1 in 4 chance their child won’t inherit any faulty gene, and so won’t have CF or be a carrier 

Where can I find out more? 

You can get more information and support from the Cystic Fibrosis Trust

We use your comments to improve our information. We cannot reply to comments left on this form. If you have health concerns or need clinical advice, call our helpline on 03000 030 555 between 9am and 5pm on a weekday or email them.

Last medically reviewed: July 2022. Due for review: July 2025

This information uses the best available medical evidence and was produced with the support of people living with lung conditions. Find out how we produce our information. If you’d like to see our references get in touch.