GLP-1 add-on doubled time in range: Ramadan

A CGM-based observational study published in Diabetes Research and Clinical Practice on 10 June 2026 found that adding a GLP-1 receptor agonist or dual GIP/GLP-1 agonist to basal-bolus insulin roughly doubled time in range during Ramadan fasting, from 36.8% to 74.4%^[1]. The study tracked 54 adults with diabetes across Ramadan 2025 using continuous glucose monitoring (CGM) and reported no increase in hypoglycaemia.

What the study measured

Researchers at Imperial College London Diabetes Centre in Abu Dhabi enrolled 54 participants from an initial pool of 140 screened individuals. They divided them into three matched cohorts of 18: one group on basal-bolus insulin alone (type 2 diabetes), a second on basal-bolus insulin plus incretin-based therapy (semaglutide or tirzepatide), and a third cohort of adults with type 1 diabetes on basal-bolus insulin^[1].

All participants wore CGM sensors throughout Ramadan. The primary outcome was time in range (TIR), defined as the percentage of the day spent between 70 and 180 mg/dL. Secondary measures included glucose management indicator (GMI), post-iftar hyperglycaemic area under the curve, and hypoglycaemia frequency^[1].

Key results

The incretin-adjunct group achieved 74.4% time in range, compared with 36.8% in the insulin-only type 2 cohort (p = 0.007). That gap was driven primarily by a 61% reduction in post-iftar glucose excursions - the spikes that typically follow the large evening meal breaking the fast^[1]. Hypoglycaemia rates did not differ between groups, and no participant in the adjunct arm discontinued treatment during the study period.

The type 1 diabetes cohort, which did not receive incretin therapy, showed intermediate TIR values. The authors noted that the post-iftar spike is the dominant glycaemic challenge during Ramadan, and that GLP-1-based agents blunt it through delayed gastric emptying and glucose-dependent insulin secretion^[1].

International consensus statements generally recommend a minimum 70% TIR for adults with type 2 diabetes. The insulin-only group fell well short of that benchmark at 36.8%, while the adjunct group exceeded it. Glucose management indicator, a CGM-derived estimate of average blood sugar, also favoured the adjunct arm, though the authors highlighted the post-iftar excursion data as the most clinically relevant finding^[1].

Why Ramadan fasting is difficult for insulin-treated patients

Ramadan requires abstaining from food and drink between dawn and sunset, typically 14 to 18 hours depending on latitude and season. For people on insulin, this creates a dual risk: daytime hypoglycaemia from extended fasting, and sharp post-iftar hyperglycaemia from large evening meals. The International Diabetes Federation and the Diabetes and Ramadan International Alliance classify insulin-treated patients as moderate-to-high risk and recommend pre-Ramadan assessment, medication adjustment, and structured monitoring^[2].

A 2025 systematic review and meta-analysis pooling 754 participants across four studies found that GLP-1 receptor agonists reduced symptomatic hypoglycaemia by 62% (risk ratio 0.38) compared with non-GLP-1 regimens during Ramadan, while also producing greater HbA1c reduction and about 2 kg more weight loss^[3]. The current study extends that evidence to insulin-treated patients specifically, a group often excluded from fasting studies because of higher perceived risk.

Both semaglutide and tirzepatide are approved for type 2 diabetes and, in some jurisdictions, for chronic weight management. Neither is specifically approved or labelled for use during religious fasting. The IDF-DAR guidelines recommend that clinicians evaluate each patient's fasting risk several weeks before Ramadan and adjust doses of insulin and any add-on therapy accordingly^[2]. GLP-1-based medications carry a well-documented gastrointestinal side-effect profile, including nausea and reduced appetite, that could affect tolerability during long fasting hours, though no participants in this study reported such problems.

Limitations to keep in mind

The sample was small (18 per arm) and drawn from a single centre in Abu Dhabi, so the findings may not generalize to populations in different climates or with different fasting durations. The study was observational, not randomised, meaning the incretin-adjunct group may have differed from the insulin-only group in ways beyond the treatment itself^[1].

The authors did not separate semaglutide from tirzepatide outcomes within the adjunct arm, so we cannot say which agent contributed more to the TIR improvement. Tirzepatide acts on both GIP and GLP-1 receptors, and whether that dual mechanism offers additional benefit during fasting conditions is unknown from this data alone.

A 2025 real-world CGM study of 702 adolescents and young adults found that time in tight range varied widely by treatment strategy, from 23.6% with multiple daily injections to 62.3% with advanced hybrid closed-loop systems^[4]. That suggests device-level differences could matter as much as medication choice, something the current study did not control for.

CGM data from a single Ramadan in a single location can show a pattern, but it cannot prove that incretin-based adjunct therapy will produce the same benefit across all climates, fasting durations, and patient profiles. Larger, multi-centre, randomised studies are needed before these findings can be translated into firm clinical guidance.

These results do not constitute a recommendation to change treatment before Ramadan without medical supervision. Anyone with insulin-treated diabetes who plans to fast should consult their healthcare provider well in advance to discuss risk stratification, medication adjustments, and monitoring plans.