Fasting during Ramadan and cystic fibrosis

Fasting during the month of Ramadan is one of the five pillars of Islam, and is required by every Muslim if they are healthy and able to do so. Fasting involves not eating or drinking from dawn to sunset. You might not have to fast if you are ill or have a medical condition like cystic fibrosis (CF), are pregnant or are travelling. However, fasting is a personal choice and we hope this information will help to support your decision making together with advice from your specialist CF team.

Each year, Ramadan moves back by 10 days, and therefore takes place at a different time each year. This means that some years the days will last for longer and people will need to fast for longer. If Ramadan takes place in the summer, the fast can be up to 18 hours long, and if it takes place in the winter it can be as short as eight hours.

Whether you have fasted for Ramadan before or not, your decision to fast may be impacted by your current health, the time of year and how you feel at the time.

Fasting can have an impact on CF diabetes (CFD), hydration, your CFTR modulators (if you take these) and your weight. This information explains how fasting might affect you and gives advice on how you can stay well.

This information was written by a team of CF dietitians, and reviewed by a Muslim hospital chaplain and Muslims living with cystic fibrosis. You can download the leaflet or read on below. 


  • What happens to my body when I fast?

    About eight hours after your last meal, your body will start to ‘fast’ and use energy stores to keep your blood sugar levels normal. For most people, fasting is not harmful. However, if you have a condition like CF, fasting might have an impact on your health.

  • How does fasting impact CF diabetes?

    If you decide to fast and have CFD, especially if you take certain tablets or insulin, you are at risk of hypoglycaemia (hypos for short). This is when your blood sugar levels become too low. The longer the fast is, the higher the risk.

    You might also experience high blood sugar levels after eating, if you eat larger meals during Ramadan at Suhoor and Iftar.

    If you are fasting it’s really important to check your blood sugar levels regularly throughout the day, and tell your diabetes team if you have any high or low blood sugar levels. Some medications for CFD might need to be adjusted if you fast so it’s really important to let them know you are planning to fast, before Ramadan.

    Choosing to fast during Ramadan is a very personal decision. For some people with CFD, fasting can be dangerous and could cause health problems. People with certain health conditions like CFD might be exempt from fasting, especially if they use insulin. Consider speaking to your Imam to see if you could delay your fast until the winter months when the days are shorter, or do something instead of fasting like donating food or money to charity, or sending money to charity to have someone fast on your behalf.

  • How does fasting impact hydration?

    It is very easy to become dehydrated during fasting, especially in warmer weather. If you become dehydrated you may experience headaches, tiredness, and difficulty in concentrating.

    If you have CF, staying hydrated can help to keep the mucus in your lungs thinner and make it easier to clear your lungs. It can also help your digestion and prevent constipation or Distal Intestinal Obstructive Syndrome (DIOS).

    There is some evidence that people with CF do not always feel thirsty, even when they need to drink. Relying on your sense of thirst is not a good indicator of how much you need to drink as you may already be dehydrated by the time you feel thirsty. Try to drink plenty of sugar-free liquids after breaking your fast. Try to avoid drinks with caffeine in like coffee or energy drinks as these can make you more dehydrated.

    Download the Trust’s nutrition leaflet on staying hydrated if you have CF to find out more about this topic. 

  • What if I am taking a CFTR modulator?

    Many people with CF are now taking CFTR modulators (also known as precision medicines), such as Kaftrio, Orkambi or Kalydeco. For these drugs to be as effective as possible, they should be taken 12 hours apart, twice a day with a food that contains fat, and pancreatic enzymes like Creon® (if required).

    If you are fasting it might be difficult for you to take your CFTR modulators correctly. Speak to your CF team before Ramadan starts to discuss this.   

  • What types of food should I eat before dawn (Suhoor)?

    You should eat complex starchy carbohydrates that release energy slowly. These include: wholegrain/multigrain bread, oat-based cereals, basmati rice, beans, pulses, lentils, fruits, vegetables, pitta bread, chapattis and semolina.

    Don’t overeat and remember to drink plenty of water to keep hydrated.

  • What types of food should I eat after sunset (Iftar)?

    It is usual to break the fast with more unhealthy foods that contain more fat and sugar. Eating healthily all year round is important, but also during Ramadan, especially if you put on weight easily or have CF diabetes. Eating complex starchy carbohydrates like those described above can help you to feel fuller for longer and help to control your blood sugar levels.

Speak to your CF dietitian for advice on maintaining a healthy weight during Ramadan. 

Remember, you know your own health and body best. Try to base your decision making on sound advice and what feels right to you during this time of setting good habits and introspection.

Whether you choose to fast or not, we wish you a healthy Ramadan and Eid Mubarak at Eid. 

Resources for CF professionals

We provide a number of different resources, programmes and awards to help support CF professionals to provide the best care possible to people with cystic fibrosis (CF) and their families.

Consensus documents

Our consensus documents are designed for clinicians and allied health professionals involved in treating patients who have cystic fibrosis.

Kareem's experience

Kareem, who is a member of our Youth Advisory Group (YAG), reviewed our information for Muslims with CF who are making decisions about fasting during the month of Ramadan. 

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