Amelia WardActor James Norton will run the London Marathon on 26 April 2026 to raise funds for Breakthrough T1D, the leading charity funding research into Type 1 diabetes — a condition he and both his mother and sister live with. The Bukhman Foundation has pledged to double-match all donations raised. Norton's announcement, shared this week on Instagram, has put a spotlight on a question doctors and endocrinologists are asked frequently: is it safe to run a marathon with Type 1 diabetes, and what does responsible management actually look like?
Why This Is More Than a Celebrity Story
James Norton is best known for his roles in Happy Valley and Grantchester, but his Type 1 diabetes (T1D) advocacy is longstanding. T1D is an autoimmune condition in which the pancreas produces little or no insulin. Unlike Type 2, it is not caused by lifestyle factors and currently has no cure. In the UK, approximately 400,000 people live with Type 1 diabetes, according to Diabetes UK.
Marathon running with T1D requires intensive planning, real-time monitoring, and often a specialist medical team. When a public figure like Norton completes a marathon while managing T1D, it challenges a persistent myth — that the condition is a barrier to physical ambition. It is not. But it does require preparation that goes significantly beyond what the average runner needs.
What the Medical Evidence Says About Exercise and Type 1 Diabetes
Exercise has a well-documented double-edged effect on blood glucose in people with T1D. Aerobic endurance exercise — like marathon running — tends to lower blood glucose levels as muscles absorb glucose for energy. This creates a risk of hypoglycaemia (dangerously low blood sugar) during or after exercise. Conversely, high-intensity sprint efforts can briefly raise glucose due to stress hormone release.
For a marathon runner with T1D, this means:
- Pre-race planning is essential. Insulin doses typically need to be reduced on training days and race day. The exact reduction depends on baseline insulin sensitivity, current glucose levels, and individual physiology — which is why a one-size-fits-all approach does not work.
- Continuous Glucose Monitoring (CGM) changes the picture significantly. Modern CGMs, such as those approved by NHS England, allow runners to see their glucose trend in real time via a wristwatch or phone. Knowing whether glucose is rising, stable, or falling — rather than just the current number — allows much faster and safer decisions.
- Carbohydrate strategy needs to be calibrated against insulin. Most marathon runners fuel with gels containing rapidly absorbed carbohydrates. For T1D athletes, this fuelling must be coordinated with insulin activity. A sports physician or specialist diabetes nurse can model this for an individual runner's profile.
- Post-exercise hypoglycaemia is a real risk for up to 24 hours after a long run. This is sometimes called "delayed onset hypoglycaemia" and can occur overnight after a long training session. Knowing this — and adjusting evening insulin accordingly — is part of the standard advice from endocrinologists.
Disclaimer: This article provides general health information only and does not constitute medical advice. Management of Type 1 diabetes requires personalised care from a qualified healthcare professional. Always consult your GP, endocrinologist, or diabetes specialist nurse before starting a new exercise programme.
What a Specialist Can Do That a General Workout Plan Cannot
Many people with T1D find that standard fitness advice — from apps, personal trainers, or generic health articles — does not account for their condition. This is not a criticism of those resources; T1D is a specialist condition. But the gap between general fitness guidance and specialist diabetes care is significant.
An endocrinologist or specialist diabetes nurse can:
- Review your insulin regimen and advise on adjustments specific to your exercise type and intensity
- Help you set CGM alarm thresholds appropriate for exercise (often wider than day-to-day thresholds)
- Advise on carbohydrate targets for different training distances
- Identify whether your current technology — pump, CGM, insulin type — is optimal for your activity level
- Flag any cardiovascular risk factors that should be assessed before beginning endurance training
For many T1D patients in the UK, accessing this level of support through the NHS depends heavily on which trust you are registered with. Waiting times for specialist diabetes review have lengthened in recent years. For those who want timely, personalised guidance before starting marathon training, a private consultation with an endocrinologist or sports medicine specialist is increasingly common.
The Technology That Is Changing Exercise for T1D Athletes
James Norton's ability to prepare for a marathon safely is, in part, a story about medical technology. A decade ago, managing T1D during a marathon required frequent finger-prick testing and significant guesswork. Today's technology has transformed this:
Continuous Glucose Monitors (CGMs) — Devices like the Libre 3 and Dexacom G7 provide a glucose reading every five minutes with trend arrows. For runners, this means knowing if glucose is at 5.2 mmol/L and stable, versus 5.2 mmol/L and falling — two very different situations that require different responses.
Insulin pumps with closed-loop capability — "Hybrid closed-loop" or "artificial pancreas" systems automatically adjust basal insulin delivery based on CGM readings. Several are now available on the NHS through specialist centres. For marathon training, these systems can be set to a specific exercise mode that reduces insulin delivery pre-emptively before and during exercise.
Smartphone integration — Most modern CGMs sync with smartphones, allowing a support crew to monitor glucose remotely during a race. For a solo runner in a field of tens of thousands, this is a practical safety measure.
How to Find a Specialist Who Understands Your Activity Level
If you have T1D and want to pursue an endurance sport, the starting point is your GP or diabetes team. Ask specifically for a referral to a specialist who has experience with athletes — this is not a routine request, but it is a reasonable one. Many NHS diabetes clinics now have a lead for sport and exercise.
You can also seek a private consultation with an endocrinologist or a sports medicine physician who lists diabetes management as a specialism. Expert Zoom connects patients with specialist health professionals across the UK. The Tom Hanks Type 2 diabetes health story explored a different dimension of diabetes management — Type 1 and Type 2 require distinct clinical approaches, and it matters that your specialist understands which you have.
What James Norton's Marathon Means for the 400,000
For the 400,000 people living with Type 1 diabetes in the UK, James Norton running 26.2 miles is both a symbol and a prompt. The symbol: T1D does not define what your body can do. The prompt: are you getting the specialist support to help your body do it safely?
Breakthrough T1D funds research into treatments including islet cell transplantation, next-generation CGM technology, and ultimately a functional cure. Every donation is double-matched by the Bukhman Foundation — amplifying the impact beyond one April Sunday in London.
If you would like to speak to a specialist about exercise management, diabetes review, or accessing newer technology on or alongside the NHS, Expert Zoom can help you find a qualified specialist in your area.
