Fasting is an important spiritual aspect of many religions. But not eating (or drinking) for long periods of time can cause major health problems if you have diabetes. This is more likely if you take insulin or other medication that can cause hypos (low blood sugar).
This page has tips and information for people living with diabetes who are thinking about fasting for a religious festival.
We have a separate page on fasting during Ramadan – one of the longest periods of religious fasting.
Fasting and religion
There is a tradition of fasting in various religions. As well as not eating food (and sometimes not drinking), fasting is also usually a time of prayer, reflection and purification.
Depending on the religion and occasion, fasting can last for different lengths of time. In Christianity, Hinduism and Judaism there tends to be individual days of religious fasting. In the Jewish calendar, for example, Yom Kippur is the holiest day when many Jews undertake a 25-hour fast. It is known as the Day of Atonement and takes place every year on a day in September or October.
Exemptions to fasting
Anyone who is putting their health at risk by fasting is usually exempt (doesn't have to take part). For example, if you have diabetes, you won't usually be expected to take part in religious fasting if:
- you treat your diabetes with insulin
- or you have diabetes complications such as damage to your eyes, kidneys or nerves in your hands and feet.
For health reasons, you aren't usually expected to fast if you're a child, elderly, pregnant or unwell.
Can you fast if you have diabetes?
Yes, in some circumstances, but it depends on your health. Deciding whether to fast or not is ultimately a personal choice. If you aren’t sure if you should fast, seek advice. Speak to your healthcare team about the possible impact on your health and ask your spiritual leader for guidance.
Preparing for a fast
If you choose to fast, talk to your doctor or healthcare team for advice on the following:
- how to manage your blood sugar levels
(for example, your doctor or healthcare team may advise you to change the time, type or dose of medication) - if you have enough medication and testing supplies
- when to check your sugar levels
- if you need to check for ketones – a chemical your body can produce if it starts to break down fat for energy
- when to break the fast
- who to contact if you become unwell.
You can also use our tips and advice below.
How to stay well when fasting
- Before the fast, eat foods that will help keep your blood sugar levels stable
This includes more slowly absorbed carbohydrate foods (that have a lower glycaemic index). But do be mindful of portion sizes of foods containing carbohydrate. You should also eat fruits, vegetables and salads. - Check your blood sugar levels more often
That way you will be able to spot if your sugar levels go too low (known as hypoglycaemia or hypo) or too high. This is more likely if you treat your diabetes with insulin or certain medications. - If you have a hypo, break the fast and treat it
If your sugar levels go too low or you have the symptoms of a hypo, such as feeling shaky, sweaty and disorientated, you must break the fast immediately and treat it with your usual hypo treatment, like glucose tablets, a sugary drink or GlucoGel, followed by a snack such as a sandwich or a bowl of cereal. - If you have high blood sugar levels break the fast and treat it
If you have high blood sugar levels (hyperglycaemia or hyper) and are also not drinking as part of your fast, it is important to break the fast by drinking water to keep yourself hydrated.
You should also treat the hypo as you normally would, such as giving insulin correction doses if you’ve been advised to do this. This will reduce the risk of dehydration and a serious condition called diabetic ketoacidosis (DKA) which would require hospital treatment. Symptoms of high blood sugar levels include feeling very thirsty, passing a lot of urine or extreme tiredness. - If you have to break your fast for any reason do not return to the fast
Continue your meals as normal for that day. You may be able to make up the fast at a later date or make a donation to help provide meals for those in need.
If you require urgent medical help you can use the NHS 111 online service.
What to eat or drink when you break a fast
When the fasting period is over or if you are breaking the fast for any reason, try to eat foods from all the food groups.
Include only small quantities of sugary and fatty foods that are often eaten as part of the celebration after the fast.
You can always try to make a healthier version of your favourite treats by choosing wholegrain options and using less oil in cooking. Try grilling, baking or dry frying food using a non-stick pan or air fryer.
To avoid dehydration, drink sugar-free and decaffeinated drinks, such as water, diet fizzy drinks or no-added sugar squashes. If you like sweet drinks, then use a sweetener instead of sugar.
