Episode 17 — GLP-1 in Type 1 Diabetes: Beyond Weight Loss, Towards Metabolic Therapy

Released 15th September 2025

Guest: Professor Viral Shah, MD

Host: John Pemberton, RD

One of the key highlights: it’s time for type 1 diabetes care to move beyond insulin alone. GLP-1s are set to be the first agents to drive this shift towards a true multi-hormone approach.

From Diabetes Management 1.0 to 2.0—are GLP-1s the catalyst?

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This summary FAQ can be downloaded. It was published on September 10, 2025. Stay up to date with the live FAQ on GLP-1RAs for T1D.

GLP-1RA-GIP-in-Type-1-Diabetes-FAQ-10-9-25pdf

This FAQ was developed to bring together the full body of evidence, alongside Dr. Shah’s personal experiences and the shared insights of colleagues.

The FAQ represents the most effective and practical guide for people with type 1 diabetes to discuss with their healthcare team, helping ensure both safety and effectiveness.

What does this Podcast episode discuss?

Unique Challenges in Type 1 Diabetes

  • Insulin delivery mismatch: injected insulin goes to the periphery, not the portal vein, driving insulin resistance.
  • Excess circulating insulin: promotes weight gain and metabolic stress.
  • Low portal insulin → high glucagon: post-meal hyperglycaemia and increased insulin needs.
  • Cycle of resistance: higher insulin doses → more weight gain → harder control.

Further reading: Overcoming Insulin Resistance in T1D

How GLP-1 Therapies Work

  • Delay gastric emptying → reduce post-meal glucose spikes.
  • Increase satiety → reduced food intake.
  • Suppress glucagon → improve post-meal stability.
  • Potentially supports residual insulin secretion.

See also: Seven Ways to Combat Insulin Resistance

GLP-1s in Type 2 Diabetes and Obesity

  • Trials in type 2 diabetes show large weight loss and HbA1c improvements.
  • Semaglutide and tirzepatide are now widely approved for T2D and obesity.
  • Evidence base is clear: these drugs shift outcomes by 30–40%, not 5–10%.

Evidence in Type 1 Diabetes

Practical Take-Homes for People with Type 1 Diabetes

  • Insulin reduction strategy: start low, go slow. Target ~30% reduction, but individualise.
  • Basal vs bolus:
    • MDI: reduce both cautiously, monitor frequently.
    • Pump: algorithm may adapt, but still reduce manually.
    • AID: systems adjust, but watch for early hypoglycaemia.
  • Monitoring:
    • Adjust based on starting HbA1c.
    • CGM critical.
  • Nutrition:
    • Protein ≥1.5 g/kg to preserve muscle.
    • Pair with resistance training.
    • Multivitamin/mineral support if appetite falls.
  • Side effects: nausea, delayed gastric emptying, hypoglycaemia if insulin not reduced enough.

Guidance for Healthcare Professionals

  • Off-label prescribing: understand risk–benefit.
  • Titrate slower in type 1 than type 2.
  • Choose agent: semaglutide may carry lower hypo risk than tirzepatide.
  • Monitor labs: LFTs, pancreatic enzymes as baseline and follow-up.
  • Modelling long-term benefit: DCCT/EDIC legacy data shows HbA1c lowering reduces complications — GLP-1 may extend this.

Future Directions

  • Triple/quad agonists in development.
  • Reimbursement challenges — evidence is strong but RCTs limited in T1D.
  • Paediatric potential — currently approved in T2D from age 12, why not T1D?

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