The GNL Podcast

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

Professor Viral Shah joins John Pemberton to explore the growing evidence for GLP-1 receptor agonists in type 1 diabetes — from the underlying mechanisms to clinical trial findings and what comes next.

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Released 15 September 2025.

A live FAQ on GLP-1 receptor agonists for type 1 diabetes is kept continuously updated. A downloadable PDF summary FAQ was published on 10 September 2025.

About the Guest

Guest: Professor Viral Shah MD, Professor of Medicine and Director of Diabetes Clinical Research, Center for Diabetes and Metabolic Diseases, IU School of Medicine. Author of multiple clinical trials and consensus guidelines on GLP-1 therapies in type 1 diabetes.
Host: John Pemberton, The Glucose Never Lies.

One key theme running through the conversation: it may be time for type 1 diabetes care to move beyond insulin alone. GLP-1 receptor agonists are emerging as a potential first step towards a true multi-hormone approach.

Unique Challenges in Type 1 Diabetes

The episode opens by exploring why insulin alone has structural limitations in type 1 diabetes:

  • Peripheral insulin delivery: injected insulin reaches the periphery before the portal vein, which tends to drive insulin resistance over time.
  • Excess circulating insulin: higher insulin levels promote weight gain and metabolic stress.
  • Low portal insulin and high glucagon: this combination tends to produce post-meal hyperglycaemia and increased insulin requirements.
  • A self-reinforcing cycle: higher insulin doses can lead to more weight gain, which in turn makes management harder.

Further reading: Overcoming Insulin Resistance in T1D

How GLP-1 Therapies Work — The Mechanism

GLP-1 receptor agonists work through several complementary mechanisms:

  • Delayed gastric emptying, which tends to reduce post-meal glucose spikes.
  • Increased satiety signals, leading to reduced food intake on average.
  • Glucagon suppression, which improves post-meal stability.
  • Potential support for any residual insulin secretion (C-peptide dependent).

Evidence in Type 1 Diabetes

What the Evidence Tends to Show — Exploration Points

The following reflects what current evidence tends to show at a population level. Individual responses vary significantly and this is worth exploring with a diabetes care team.

Insulin Adjustment Pattern

Studies suggest targeting around a 30% reduction in insulin doses as a starting point, with slow titration and close monitoring. Individual adjustment is essential. Basal and bolus requirements may both change, in different proportions depending on the therapy used.

Monitoring Approach

CGM is described as critical during GLP-1 initiation. Adjustments based on CGM data help identify how individual glucose patterns are changing. Starting HbA1c influences how aggressively monitoring is needed early on.

Nutrition During GLP-1 Use

Because GLP-1 therapies reduce appetite significantly, ensuring adequate protein intake (discussed in the evidence as approximately 1.5 g per kg) to preserve muscle mass is a practical consideration. Resistance training alongside is often recommended. Multivitamin and mineral support may be worth discussing if appetite falls substantially.

Side Effects to Be Aware Of

The most common side effects discussed in the literature are nausea, delayed gastric emptying, and hypoglycaemia if insulin is not adjusted sufficiently. These are worth discussing with a diabetes care team before starting.

Future Directions

  • Triple and quadruple agonist agents are in development and may offer further metabolic benefits.
  • Reimbursement remains a challenge: the evidence base is growing but large randomised controlled trials in type 1 diabetes remain limited.
  • Paediatric potential: currently approved in type 2 diabetes from age 12, the evidence picture in type 1 diabetes is evolving.

Related GNL Resources

Evidence References

Consensus and guidelines:

This content is for educational exploration only. It describes average responses and general principles. It is not medical advice and cannot replace individual clinical guidance from your diabetes care team.

GLP-1 therapies for type 1 diabetes remain off-label in most settings. All decisions about starting, adjusting, or stopping any therapy should be made with your diabetes care team.

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