Enzyme dosing in cystic fibrosis 

In cystic fibrosis (CF) sticky mucus blocks the passages from the pancreas to the small intestine which stops the enzymes working, so the food cannot be digested or absorbed by the body.

How many enzymes?

  • „„Everybody needs a different amount of enzymes depending on how much food is eaten and how much fat, protein and carbohydrate is in the food.  
  • „„High fat meals, such as those containing cheese or fried foods, need more enzymes.
  • „„High fat snacks may need as many enzymes as a meal.

Which foods do not need enzymes?

  • „„A few foods do not need enzymes.
  • These are mainly sugary foods containing very little fat or protein:
    • fruit
    • fruit juice and squash
    • jam
    • fizzy drinks
    • jelly
    • boiled or
    • chewy sweets
    • ice lollies
    • most vegetables

Handy tips…

  • „„Enzymes are best swallowed whole.
  • „„Do not chew or crunch enzymes as this stops them working properly.
  • „„Store enzymes in a cool dry place, away from heat and sunlight.
  • „„Keep a pot of enzymes with you (in your lunchbox, on the kitchen table) to remind you to take them.

Looking at labels to work out enzyme doses

  • „„Food labels contain nutrition information. Looking at the amount of fat per serving or portion tells us how many enzymes are needed.
  • „„On some packets fat is given per serving, sometimes it is given per 100g of food.
  • To work out how much fat is in a portion: Look at the amount of fat per 100g, divide this figure by 100, then multiply by the portion size.
  • Example: 35g packet of crisps contains 30g fat per 100g so 30/100 x 35g = 10g fat per portion.
Compiled by: 
The Cystic Fibrosis team in collaboration with the Child and Family Information Group
Last review date: 
April 2014


Please read this information sheet from GOSH alongside the patient information leaflet (PIL) provided by the manufacturer. If you do not have a copy of the manufacturer’s patient information leaflet please talk to your pharmacist. A few products do not have a marketing authorisation (licence) as a medicine and therefore there is no PIL.

For children in particular, there may be conflicts of information between the manufacturer’s patient information leaflet (PIL) and guidance provided by GOSH and other healthcare providers. For example, some manufacturers may recommend, in the patient information leaflet, that a medicine is not given to children aged under 12 years. In most cases, this is because the manufacturer will recruit adults to clinical trials in the first instance and therefore the initial marketing authorisation (licence) only covers adults and older children.  

For new medicines, the manufacturer then has to recruit children and newborns into trials (unless the medicine is not going to be used in children and newborns) and subsequently amend the PIL with the approved information. Older medicines may have been used effectively for many years in children without problems but the manufacturer has not been required to collect data and amend the licence. This does not mean that it is unsafe for children and young people to be prescribed such a medicine ‘off-licence/off-label’. However, if you are concerned about any conflicts of information, please discuss with your doctor, nurse or pharmacist.