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Keeping kidneys healthy during fasting

This information is for anyone who is preparing to observe a period of fasting, for example during a religious time.

What happens to the body 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.

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.

Fasting remains a personal choice

Fasting is an obligation for Muslims and if you choose to fast it's important to be prepared. Speak with your healthcare team in advance of fasting for a risk assessment and plan for any medication changes and monitoring that may be required in order to fast safely.

"Muslims believe their bodies are a gift from God and we have a responsibility to look after it so while fasting can be challenging, it should never be detrimental to our health." Dr Sahira Dar

Being exempt from fasting

People can also be exempt from fasting if they:

  • are children (under the age of puberty)
  • are elderly
  • are sick or have a certain health condition
  • have learning difficulties
  • are travelling
  • are pregnant or breastfeeding
  • menstruating.

If you’re showing any symptoms of Covid-19, it is advisable not to fast. If you're fasting during Ramadan, getting the coronavirus vaccine does not break your fast.

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 is key to keeping your body in good shape. You have a shorter window than usual to fit in the advised water intake, about 2 litres (2litres=8 glasses). 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.


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.

Fasting 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 Ramadan 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.

Risks of fasting

Although fasting has been shown to improve fatigue, mood, and quality of life in people with and without chronic health conditions, adjustment of drug regimens may be necessary in many conditions.

There is concern that if you have chronic kidney disease (CKD) you can experience electrolyte imbalance and worsening of renal function but evidence shows that if you seek medical advice and adhere to an agreed plan those risks are reduced.

Recommendations for kidney patients

Kidney experts from across the UK including Dr Shafi Malik have researched the impact of fasting on kidney patients and have made the following recommendations.

Categorizing risk based on IDF-DAR risk categories


*Categorizing risk based on IDF-DAR risk categories - table from Effects of fasting on patients with chronic kidney disease during Ramadan and practical guidance for healthcare professionals.


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.

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.

  • People may partake in the non-fasting elements of Ramadan, which is also a time of charity, spirituality, and communal prayers.
  • If the length of a summer fast is the prohibitive factor, then patients can alternatively fast during the winter months.
  • 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.
  • If advised you're unable to fast, even in the future, then an alternative is fidaya (feeding the poor).

Further advice and information

The Muslim Council of Britain has the latest guidelines and advice for Muslims fasting during the month of Ramadan to help them make the most of the blessed month. This information is also useful for the friends, neighbours and colleagues of Muslims.

Effects of fasting on patients with chronic kidney disease during Ramadan and practical guidance for healthcare professionals. Shafi Malik, Amir Bhanji, Husham Abuleiss, Rizwan Hamer, Shahzad H Shah, Rafaqat Rashad, Naushad Junglee, Salman Waqar, Nazim Ghouri. Clinical Kidney Journal, Volume 14, Issue 6, June 2021, Pages 1524–1534.

Advising patients with existing conditions about fasting during Ramadan - this paper in The BMJ is aimed at healthcare professionals, however it includes some useful information for patients who are looking to fast.

Reviewed March 2022

If you are from a South Asian background, you are five times more likely to get kidney disease.

We have supported research in the field of health inequalities since 2001, and have invested around £2.4 million in this research so far.

Research has found that South Asian babies are born with smaller kidneys, which could be more prone to damage over a lifetime. A research project funded by Kidney Research UK is studying children at age 8-11 to see whether kidney size at birth is a factor in developing kidney disease later.

Jelina's story.

Award winning human rights lawyer, Jelina Berlow-Rahman built her own law firm whilst also managing a gruelling dialysis regime.

Jelina’s kidneys started failing at the age of 18. Aching hands and painful lesions on her lips and tongue led her to have tests which revealed she had an aggressive form of lupus.

"I donate to Kidney Research UK every Ramadan to help the fight against kidney disease. I do this for people like me that have been affected and for people that can’t take part due to ill health." Jelina Berlow-Rahman

After four punishing years on dialysis, Jelina had a successful kidney transplant in December 2009. Today, Jelina continues her brilliant career, is a staunch supporter of Kidney Research UK and proud mother to Aliyah.

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