Type 1 Diabetes Runners Finish Marathons Safely With CGM Guidance

Real‑Time Data Transforms Endurance Strategy

Researchers at the European Association for the Study of Diabetes (EASD) meeting in Milan this week presented data showing that athletes with type 1 diabetes can complete full‑marathon distances without serious glucose‑related incidents when they use continuous glucose monitoring (CGM) and follow a structured management plan. The study followed 112 runners, both men and women, aged 18‑45, who trained for and ran the 2025 Berlin Marathon under supervised conditions.

The investigators equipped participants with CGM devices that recorded glucose levels every five minutes throughout training and race day. Runners received individualized carbohydrate‑loading protocols, real‑time alerts for hypo‑ and hyper‑glycaemia, and a pre‑race insulin‑adjustment guide. Over 98 % of the athletes finished the 42.2‑kilometre course, and none experienced severe hypoglycaemia requiring medical assistance. Average glucose stayed within the target 70‑180 mg/dL range for 85 % of race time, a marked improvement over historic reports where uncontrolled glucose spikes led to drop‑outs and hospital visits.

Continuous monitoring allowed participants to see trends and act instantly. „When my CGM warned me of a dip at the 20‑kilometre mark, I took a quick sip of glucose gel and kept my pace,” said Elena Rossi, a 29‑year‑old runner from Turin. The study team noted that alerts prompted carbohydrate intake an average of 3.2 minutes before glucose fell below 70 mg/dL, preventing full‑blown hypoglycaemia. Moreover, the CGM data helped athletes fine‑tune insulin dosing during the weeks leading up to the marathon, reducing the incidence of post‑exercise hyperglycaemia that can impair recovery.

Can Marathon Training Be Safe for All Type 1 Diabetics?

Researchers also compared the CGM‑guided group with a control cohort that relied on traditional finger‑stick testing. The control runners experienced a 12 % higher rate of glucose excursions outside the safe window and a 5 % higher dropout rate. The findings suggest that CGM technology not only improves safety but may also enhance performance by stabilising energy availability throughout the race.

While the results are promising, experts caution that success depends on disciplined preparation and access to reliable CGM devices. „The technology is a tool, not a magic bullet,” said Dr. Marco Bellini, lead author of the study. „Athletes must still work closely with endocrinologists to tailor insulin and nutrition plans.” The study excluded participants with recent severe hypoglycaemia episodes or cardiovascular complications, indicating that individual health status remains a key factor.

Looking ahead, the team plans to expand the research to ultra‑marathon distances and to test integration of CGM data with wearable heart‑rate monitors for even finer control. If broader adoption follows, the barrier that type 1 diabetes has traditionally posed to endurance sports could diminish, opening doors for more inclusive athletic events worldwide.

Frequently Asked Questions

How does CGM differ from traditional glucose testing for runners? CGM provides continuous, real‑time glucose readings and alerts, allowing athletes to respond to trends instantly, whereas finger‑stick tests give only isolated snapshots.

Is a CGM device required for all type 1 diabetic athletes? While not mandatory, the study shows CGM markedly reduces the risk of dangerous glucose swings during long‑duration exercise, making it highly advisable for marathon training.

What precautions should runners take before attempting a marathon? They should consult their diabetes care team, follow a personalized insulin and carbohydrate plan, practice with CGM during long training runs, and have emergency glucose sources readily available.