Can people with diabetes or prediabetes fast safely? Doctor explains

Fasting is often associated with religious observances, weight management, and potential metabolic benefits. However, for people with prediabetes or diabetes, going without food for extended periods can affect blood sugar levels, hydration, and medication requirements. While some people may be able to fast safely, others could face complications that require medical attention.The risks also differ depending on whether a person has prediabetes or established diabetes, the type and duration of the fast, and whether they take medicines that lower blood sugar.Dr. Ashok Kumar Jhingan, Principal Director, Centre for Diabetes, Thyroid, Obesity & Endocrinology, BLK-Max Super Speciality Hospital, Delhi, explains that fasting can be safe for some people, but it requires an individual assessment, particularly for those already diagnosed with diabetes.CAN PEOPLE WITH DIABETES AND PREDIABETES FAST?People with prediabetes generally have a lower immediate risk of fasting-related hypoglycaemia, or low blood sugar, particularly if they are not taking glucose-lowering medication. However, prolonged fasting, inadequate fluid intake, and overeating after a fast can still affect blood sugar regulation. For people with established diabetes, the risks may be greater, especially if they use insulin or sulfonylureas, a class of medicines that can cause blood sugar levels to fall too low when meals are skipped."Fasting can be safe for some people with prediabetes and diabetes, but its safety depends on their metabolic health, medications, duration of fasting, and the presence of complications," Dr. Jhingan explains. People with diabetes may experience hypoglycemia, high blood sugar, or dehydration during fasting. In certain circumstances, particularly when insulin levels are insufficient, diabetic ketoacidosis can also occur, making medical assessment essential before undertaking prolonged or religious fasts.For those with prediabetes, sustainable dietary changes, weight management, and regular physical activity remain important ways to improve metabolic health. People with diabetes should consult their treating doctor before changing meal timings or attempting extended fasting.CAN INTERMITTENT FASTING IMPROVE INSULIN SENSITIVITY?Intermittent fasting involves alternating periods of eating and fasting. It has gained popularity as a strategy for weight management and improving metabolic health, but its benefits depend on how it is practised and the individual's health status.According to Dr. Jhingan, intermittent fasting may improve insulin sensitivity in people with prediabetes, particularly when it helps them achieve sustained weight loss and reduce excess visceral fat. These changes can improve glucose regulation and may lower the risk of progression to type 2 diabetes.However, fasting is not necessarily more effective than other dietary approaches."The benefits are not exclusive to fasting. Evidence suggests that intermittent fasting is generally comparable to conventional calorie restriction for weight loss," he says.Diet quality, physical activity, adequate sleep, and the ability to maintain healthy habits over time remain important.For people already living with type 2 diabetes, intermittent fasting may help with weight reduction and improve some measures of blood sugar control. However, medication adjustments may be needed to prevent low blood sugar.People with type 1 diabetes require particular caution and specialist supervision. Intermittent fasting should not be considered a replacement for prescribed diabetes medication.THREE MAJOR RISKS OF FASTING FOR PEOPLE WITH DIABETESThe three main concerns associated with fasting are hypoglycaemia, hyperglycaemia and dehydration. The likelihood of these complications depends on the person's glucose levels, medication, kidney function, other health conditions, and the duration of the fast.Low blood sugar: Hypoglycaemia is a significant concern for people taking insulin or sulfonylureas. Skipping meals while continuing the usual medication dose can cause blood sugar levels to drop dangerously low. Symptoms may include sweating, trembling, palpitations, dizziness, hunger and confusion. Severe cases can lead to seizures or loss of consciousness.High blood sugar: Hyperglycaemia may occur when people reduce or skip medication without medical advice, become dehydrated or consume large amounts of sugary foods and refined carbohydrates when breaking the fast. Severe hyperglycaemia can lead to medical emergencies, including diabetic ketoacidosis in susceptible individuals.Dehydration: Dry fasting, during which both food and fluids are restricted, can increase the risk of dehydration. High blood sugar can also cause frequent urination and fluid loss. Certain medications and underlying kidney problems may further increase the risk.People with prediabetes who do not take glucose-lowering medication generally have a lower risk of medication-related hypoglycemia. However, prolonged fasting and dehydration can still cause weakness, dizziness, and other complications.WHAT SHOULD PEOPLE WITH DIABETES EAT BEFORE AND AFTER FASTING?Meal planning depends on the type of fast. Intermittent fasting, religious fasting, and dry fasting have different requirements, particularly when it comes to fluid intake.Before a fast, Dr. Jhingan recommends a balanced meal containing complex carbohydrates, protein, fiber, and healthy fats. Options may include oats, whole grains, pulses, vegetables, and suitable protein sources. Meals should provide adequate nutrition without excessive refined carbohydrates, sugar, or salt.When breaking a fast, people should avoid compensating for missed meals by overeating or consuming excessive sweets, fried snacks, and sugary drinks.A moderate, balanced meal containing vegetables, a suitable protein source, and controlled portions of high-fiber carbohydrates, such as whole grains or pulses, can help support more stable blood sugar levels.During intermittent fasting, water should be consumed regularly. Unsweetened tea or black coffee may be suitable for many adults, depending on individual medical circumstances. During religious or dry fasting, fluid restrictions require additional precautions, particularly for people with diabetes."If blood glucose falls dangerously low, the fast must be broken and hypoglycemia treated immediately," Dr. Jhingan cautions.People should also maintain adequate fluid intake during periods when drinking is permitted. Portion sizes, meal timing, and food choices should be tailored to individual glucose levels, medication, and nutritional needs.WHO SHOULD AVOID FASTING?Fasting may be unsafe for people with poorly controlled diabetes, recurrent or recent severe hypoglycemia, impaired awareness of low blood sugar, a recent episode of diabetic ketoacidosis, advanced kidney disease, significant frailty, or serious acute illness.Pregnant women with diabetes should not undertake fasting without specialist guidance. People with type 1 diabetes, those requiring multiple daily insulin injections, and individuals with significant diabetes-related complications also need particularly careful assessment.Medication management is another important consideration. Insulin and sulfonylureas may require adjustments to reduce the risk of hypoglycemia, while other medicines may need changes in timing or additional precautions depending on the type of fast."Medication should never be stopped, reduced, or rescheduled independently," Dr. Jhingan advises.People should discuss their fasting plans with their treating doctor beforehand, including whether their medication schedule, blood sugar monitoring and fluid intake need to change.WHEN SHOULD YOU BREAK A FAST IMMEDIATELY?People with diabetes who choose to go fast need to monitor their blood glucose as advised by their healthcare team. Checking blood sugar is an important safety measure and does not, by itself, make a fast unsafe.According to Dr. Jhingan, the fast should be stopped immediately if blood glucose falls below 70 mg/dL or rises above 300 mg/dL. A reading below 70 mg/dL requires prompt treatment for hypoglycaemia, while a reading above 300 mg/dL warrants ending the fast and following the person's medical action plan, including seeking urgent medical advice when indicated.A blood glucose reading between 70 and 90 mg/dL early in a fast should be rechecked promptly, with further action guided by the individual's medical plan.Other warning signs include dizziness, sweating, trembling, confusion, unusual weakness, symptoms of significant dehydration or feeling acutely unwell. Severe symptoms, loss of consciousness or suspected diabetic ketoacidosis require emergency medical attention.Physical activity also needs consideration. Strenuous exercise during prolonged fasting, particularly towards the end of the fasting period, may increase the risk of hypoglycemia and dehydration. Gentle movement may be appropriate depending on an individual's health and medical advice.Fasting is not automatically unsafe for everyone with prediabetes or diabetes, but neither is it suitable for everyone. The potential benefits depend on the person's health, dietary choices and ability to maintain sustainable habits, while the risks are influenced by medication, hydration and glucose control.For people with prediabetes, a balanced diet, weight management and regular physical activity remain important priorities. For those with diabetes, medical assessment, appropriate blood sugar monitoring and medication planning are essential before attempting a prolonged or religious fast.As Dr. Jhingan emphasises, fasting should be a medically informed decision, not a test of willpower. Maintaining safe blood sugar levels and preventing complications must always take priority over completing a fast.- Ends