Fasting may support weight loss for some people with prediabetes, but it can also trigger dangerous blood sugar swings and dehydration, particularly for those using insulin or sulfonylureas.
For people with prediabetes or diabetes, fasting is not a simple yes-or-no decision. It may be manageable for some, but it can also disrupt blood sugar control, alter medication needs and increase the risk of dehydration, according to an article from India Today based on guidance from Dr Ashok Kumar Jhingan, principal director at BLK-Max Super Speciality Hospital in Delhi. The National Institute of Diabetes and Digestive and Kidney Diseases similarly warns that anyone with diabetes should treat fasting as a medical issue, not merely a lifestyle choice.
The key question is not only whether a person has diabetes, but how well it is controlled, which medicines they take and how long they plan to go without food. People with prediabetes who are not using glucose-lowering drugs generally face a lower immediate risk of low blood sugar, yet prolonged fasting and poor fluid intake can still cause dizziness, weakness and other problems. For people with established diabetes, especially those using insulin or sulfonylureas, the risk rises because skipped meals can trigger hypoglycaemia, while reduced medicines or rebound eating can push glucose too high. Cleveland Clinic also advises that fasting should not begin without a discussion with a clinician.
Intermittent fasting has attracted attention because it can help some people lose weight and improve insulin sensitivity. India Today reported that Jhingan said it may be useful for people with prediabetes, particularly if it leads to sustained weight loss and less visceral fat, the deep abdominal fat linked with insulin resistance. But the evidence does not suggest fasting is uniquely powerful: he said its benefits are broadly comparable with conventional calorie restriction, a view echoed by other clinical guidance that stresses overall diet quality, physical activity and sleep as the foundations of metabolic health. Research summaries have also suggested that time-restricted eating can modestly improve fasting insulin and A1C in some people with prediabetes, although results depend on what is eaten and whether the pattern can be maintained.
The main medical dangers are low blood sugar, high blood sugar and dehydration. Hypoglycaemia is the most immediate concern for people taking insulin or sulfonylureas, because the usual dose may become too strong if meals are skipped. Hyperglycaemia can develop if medication is missed, fluid intake falls or people overindulge in sugary or refined foods when the fast ends. Severe cases can become emergencies, including diabetic ketoacidosis in vulnerable patients. Mayo Clinic and the NIDDK both underline that dangerous swings in glucose can cause serious illness, and that dehydration makes the picture worse, particularly if kidney function is already impaired.
Meal planning matters before and after the fasting window. The advice from India Today is to eat a balanced meal beforehand, built around complex carbohydrates, protein, fibre and healthy fats, rather than refined starches and sugar. When breaking the fast, the safer approach is a moderate meal with vegetables, a protein source and controlled portions of whole grains or pulses. That is especially important because large, sugary meals can send glucose sharply higher after a long gap without food. During non-fasting hours, regular fluid intake is essential; during dry fasting, when even water is restricted, the risk of dehydration increases further.
Not everyone should attempt fasting. India Today said fasting may be unsafe for people with poorly controlled diabetes, recent severe hypoglycaemia, impaired awareness of low blood sugar, advanced kidney disease, a recent episode of diabetic ketoacidosis, frailty or serious acute illness. Pregnant women with diabetes, people with type 1 diabetes and those on multiple daily insulin injections need particularly careful specialist advice. Medication must never be altered on one’s own, and any plan should be agreed in advance with a doctor. If blood glucose falls below 70 mg/dL or rises above 300 mg/dL, the fast should be broken immediately; warning signs such as confusion, trembling, severe weakness or signs of dehydration call for urgent medical help.
Disclaimer: This content is for informational purposes only and is not intended to be a substitute for professional medical judgment, advice, diagnosis, or treatment.
