Looking after your kidney health during fasting
This information is for anyone who is considering fasting, for example, during a religious time. It includes fasting advice, information and personal experiences.
In partnership with the British Islamic Medication Association we have produced a factsheet about fasting with kidney disease during Ramadan. This is available in English, with other language options soon to be published.
What happens to the body and kidneys during fasting
For the first 4-6 hours after your last meal your body uses up all the energy supplied by that meal. After this point, the liver starts to make more glucose, which produces new energy.
If you are healthy and are not taking medication that affects your hydration, your kidneys should not be affected by careful fasting. Fasting can in the summer months be as long as 20 hours and some with underlying health conditions may not be able to fast for such long periods. The key is to understand your body health before deciding to fast, and being aware of any changes to your health during the period of fasting.
Good preparation and planning can avoid problems during fasting. Dehydration can have a negative impact on the kidneys, building up a waste and acids in the body, and potentially leading to kidney stones, urinary tract, kidney damage and disease if left untreated. Similarly, certain foods can put extra strain on the organs meaning that an appropriate diet is even more necessary while fasting.
Choosing whether to fast
Before you fast, it can be reassuring to know that you are in the best health possible for you. Underlying conditions that you may not be aware of can have a serious impact on your health during fasting if you are unprepared.
Many mosques offer pop-in clinics, why not drop in and get yourself a free health MOT as you prepare for Ramadan?
Helping to protect your kidneys
Even if you are not a kidney patient, you can take steps ahead of Ramadan to help protect your kidneys:
- If you have a family history of diabetes (the most common cause of kidney disease), make sure you have an annual check for diabetes yourself.
- High blood pressure is another common cause of kidney disease. Get your blood pressure tested; you can buy home kits or many pharmacies offer this service.
- If you are being treated for high blood pressure, consult your doctor before fasting and get your kidney function checked. Some medications can affect hydration, which can become all the more serious during fasting.
Things to consider if you're a kidney patient
If you are a kidney patient it is important to check in with your healthcare team to see how you are currently managing your kidney disease. This can help you to understand how fasting can affect you and your kidneys, how to reduce any risks and stay as healthy as possible.
Those with health conditions such as kidney disease may be able to fast with medical supervision while others may be exempt. It is important to discuss the safety and suitability of fasting with a healthcare professional in plenty of time before commencing fasting.
How to fast safely
It is important to have a plan to help you fast safely; if you have a healthcare team they can help you develop this.
Following any necessary medication or dialysis treatment changes, it is advised to consider a trial of fasting for a few days prior to the start of Ramadan with close monitoring to establish safety and tolerability.
Consider your kidneys while fasting
Remember, it’s a fast, not a feast! When breaking your fast, try not to go overboard. Watch portions and calories; food should be balanced and healthy.
- A high glucose-containing food to start off with will give you the burst of energy you’ll be needing, such as fruit juice or a salad.
- Space out your food and drinks during the period in which you can eat – go for small meals including complex carbohydrates (whole grains like brown rice, starchy vegetables and non-starchy vegetables, beans and legumes like lentils, kidney beans and chick peas).
Hydration
Hydration is key to keeping your body in good shape. Drink the recommended amount of water (six-eight glasses) between sunset and dawn. If you have been advised a fluid restriction it is important to stick to it. Your hydration levels should be fine provided you do consume that amount between sunset and sunrise. A good plan for doing this is:
- break your fast by first drinking one or two glasses of water before you eat
- another two glasses after your iftar meal
- two more glasses during nightly prayers
- two more glasses with your suhoor meal.
Sleep
Don’t underestimate the importance of sleep. Changes to your sleep routine can be more impactful than fasting. Having the right quality of sleep allows for your body to refresh, reenergise and heal, and that allows for things like your gut, your kidneys to rest and recuperate. Quality is more important than quantity. Really consider how to build in enough rest (if not actual sleep). Different options work for different people:
- Can you nap after your early suhoor meal and start work later?
- Would you prefer to start your day early and build in a midday siesta?
- Perhaps a nap before starting preparations for the iftar meal and prayers works best.
Watch a video from Dr Sahira Dar about the importance of sleep.
Is fasting good for your kidneys? How to fast safely as a kidney patient
If you are a kidney patient, it’s important to have a plan to help you fast safely – your healthcare team can help you with this. You may wish to consider a trial of fasting before with close monitoring to make sure your medications and treatments are suitable to keep you as healthy as possible.
Do speak to your healthcare team about the kind of foods that you may need to avoid and how to keep your hydration at the right level.
Recommendations for kidney patients
Kidney experts in the UK along with Islamic scholars have developed the following recommendations when fasting.
Patients at low-moderate risk:
- People with chronic kidney disease stages 1, 2 or 3, with stable kidney function.
- Chronic kidney disease patients who get frequent urinary tract infections or kidney stones.
- Kidney transplant patients with stable kidney function, optimized immunosuppression and not in the below categories.
Recommendation: listen to medical advice
Patients at high risk:
- People with chronic kidney disease stages 1,2 or 3, with unstable kidney function (usually rapidly declining eGFR, experience fluid overload and/or are frail).
- Chronic kidney disease patients with electrolyte abnormalities (usually high potassium or low sodium).
- Patients at risk of dehydration due to fluid restriction or are taking diuretics (water tablets)
- Patients on specific medications such as: ramipril, losartan, dapagliflozin and spironolactone (these are some examples).
- Kidney transplant patients with reduced kidney function (those with eGFR 30-60 ml/min.).
Recommendation: Should not fast
Patients at very high risk:
- Patients on all forms of dialysis.
- Patients with chronic kidney disease stages 3-5 with a history of cardiovascular disease.
- Patients with chronic kidney disease stages 4-5 who are not on dialysis – except those who discussed risks and had counselling from their specialist taking into account how well their kidneys are functioning, their fluid balance, potassium level among other factors.
- Kidney transplant patients who underwent a transplant in the last 12 months.
- Transplant patients with unstable kidney function, recent rejection or atypical infections.
Recommendation: Must not fast
Notes to consider:
Risk of fasting needs to be individualised, some in the high-risk category may be able to fast with careful guidance and monitoring by a specialist.
Transplant patients on twice daily immunosuppression were considered very high risk in the peer reviewed paper written by the same authors of this guidance. This was based on fasting during summer months. Although fasting whilst on twice daily dosing is now possible, patients will need an individualised approach with their transplant specialist to avoid significant risk.
Fasting during Ramadan
Ramadan is a religious holiday celebrated by Muslims and runs for 29 or 30 days, it ends with Eid al-Fitr.
The majority of Muslims will choose to fast and follow special nightly prayers during the month of Ramadan. Fasting means no eating or drinking from sunrise to sunset each day of Ramadan, which can impact on some of our bodily functions. Find out more and discover how you can maintain the health of your kidneys during this special time in the factsheet we have devised with the British Islamic Medication Association.
People who are ill or have underlying health conditions can be religiously exempt.
If you are exempt from fasting, or choose not to fast, there are alternative ways to observe Ramadan.
- If the length of a summer fast is the prohibitive factor, then patients can alternatively fast during the winter months when days are shorter and cooler
- If you are concerned fasting may make your condition worse, consider non-consecutive fasts - such as alternate days or a one day break after every two to four fasts.
- People may partake in the non-fasting elements of Ramadan, which is also a time of charity, spirituality, and communal prayers.
- If advised you're unable to fast, even in the future, then an alternative is fidaya (religious donation).
Consider speaking to your local imam, scholar or trusted religious authority for more advice on alternatives to fasting.
Reviewed February 2025
Fasting factsheet
In partnership with the British Islamic Medication Association we have produced a factsheet about fasting with kidney disease during Ramadan.
Versions in additional languages are in development and will be added to this page shortly.
Rayhan's experience
Rayhan was diagnosed with IgA nephropathy in 2022. At just 16 years old, he began dialysis treatment.
For Rayhan and his mother, several changes have become necessary in the way they study, work, eat, drink, socialise and practice their religion, including how they observe Ramadan.