Is fasting safe for people with diabetes?
Fasting can be safe for some people with type 2 diabetes when it is planned carefully with medical supervision, but it can be risky—especially for people taking insulin or sulfonylureas, and for those with type 1 diabetes[2][5].
Many studies and reviews suggest fasting may improve insulin sensitivity, reduce body weight, and lower fasting glucose in some people, but benefits depend on the fasting method, medication changes, and consistent follow up with health professionals[5][2][8].
Why fasting affects people with diabetes differently
– Fasting reduces the incoming calories the body uses for energy, which can lower blood glucose levels and reduce the need for some diabetes medications[2][6].
– In people on insulin or insulin-stimulating drugs, skipping meals can cause dangerous low blood sugar, called hypoglycemia[1][2].
– Conversely, long or poorly managed fasts can trigger high blood sugar from stress hormones or, in people with little or no insulin (for example with type 1 diabetes), diabetic ketoacidosis[1][6].
Which groups should be especially cautious or avoid fasting
– People with type 1 diabetes generally face a higher risk of severe hypoglycemia or ketoacidosis and should not fast without expert endocrine care[4].
– People who use insulin or sulfonylureas need close dose adjustments and frequent glucose monitoring if they attempt fasting[2][1].
– Pregnant or breastfeeding people, those with advanced kidney disease, recent diabetic complications, or a history of severe hypoglycemia should avoid unsupervised fasting[1][2].
Potential benefits reported in studies
– Intermittent fasting and time‑restricted eating have been linked to weight loss and improvements in fasting insulin, insulin resistance, and some cardiometabolic measures when compared with usual diets in some trials[5][2].
– Some controlled fasting or fasting-mimicking approaches produced weight loss, lower blood pressure, and reduced body fat in small trials, outcomes that can help reduce diabetes risk or improve control when maintained[8][6].
Practical safety steps to consider before and during fasting
– Talk with your diabetes care team first so medications (especially insulin and secretagogues) can be adjusted and a monitoring plan made[2][1].
– Increase the frequency of blood glucose checks during fasting and breaking periods; consider continuous glucose monitoring if available and recommended by your clinician[6][2].
– Stay well hydrated and avoid excessive caffeine or diuretics while fasting to reduce dehydration risk[1][2].
– Begin with modest, shorter fasts (for example a supervised overnight or time-restricted eating window) rather than long or frequent multi-day fasts until safety is clear[1][2].
– Know the warning signs of hypoglycemia and hyperglycemia and have a plan for rapid treatment and when to stop the fast and seek care[1][2].
How providers manage medication and monitoring
– Clinicians may lower insulin doses, change timing of injections, or pause certain oral medications on fasting days; any change must be individualized and supervised[2].
– Regular follow up and lab checks (including A1C and kidney function) are important to ensure fasting does not cause harm over time[5][2].
Deciding whether to try fasting
– For people with well controlled type 2 diabetes, few other health problems, and close clinical support, a carefully planned intermittent fasting approach may be an option to explore[5][2].
– For people on intensive insulin regimens, with type 1 diabetes, pregnancy, advanced complications, or unstable control, fasting is generally contraindicated without specialized care[4][1].
– The American Diabetes Association has not issued universal endorsements for intermittent fasting in diabetes, and the evidence is still evolving; individualized medical advice is essential[2][5].
Sources
https://www.goodrx.com/well-being/diet-nutrition/intermittent-fasting-diabetes
https://www.massgeneralbrigham.org/en/about/newsroom/articles/pros-and-cons-of-intermittent-fasting
https://timesofindia.indiatimes.com/life-style/fasting-diabetes-benefits-risks-and-safety-tips/articleshow/126030950.cms
https://www.science.org/content/article/five-day-fasting-diet-could-fight-disease-slow-aging
https://www.healthshots.com/brand-stories/fasting-and-diabetes-how-an-age-old-practice-is-finding-its-place-in-modern-care/
