A small observational study from the Poznań Marathon shows athletes with type 1 diabetes can safely finish races using individualized glucose and hydration plans.
On September 18, 2026, MedicalXpress reported on new clinical research scheduled for presentation at the upcoming European Association for the Study of Diabetes Annual Meeting in Milan. The small observational study examined 10 amateur marathon runners with type 1 diabetes during the 2025 Poznań Marathon. Researchers tracked their physiological responses alongside a control group of 10 amateur runners without the condition. The resulting data provides a fascinating look at how ambitious athletes with metabolic conditions can safely manage a standard 42 kilometer race.
Historically, fear of hypoglycemia has acted as a major barrier to physical activity. Study authors note that this fear affects up to 45 percent of people with type 1 diabetes. The primary conclusion from the researchers indicates that athletes with this condition can complete a marathon safely and perform on par with their peers. This positive outcome depends entirely on careful preparation and highly individualized risk management.
The research marks a shift away from treating marathon participation as categorically unsafe for athletes with type 1 diabetes. Instead, doctors now point to tailored insulin adjustments, precise carbohydrate planning, and continuous medical supervision as the foundation for safe endurance events. Safety in this context means having an effective management strategy rather than a complete absence of risk. The evidence remains preliminary, as it relies on a single event and has not yet been identified as a peer reviewed journal publication.
To understand these findings, we need to look at how the researchers set up the monitoring process. The study group with type 1 diabetes included eight men and two women. They had a mean age of 35.4 years, a median diabetes duration of 16.5 years, and a median HbA1c of 6.4 percent. All 10 runners with the condition successfully completed the standard 42 kilometer course.
Performance between the two groups remained remarkably similar. The runners with type 1 diabetes reported a median finishing time of 228 minutes. The control group finished with a median time of 248 minutes, and the researchers noted no statistically significant performance difference between the two cohorts. The methodology relied heavily on customized pre race insulin reductions based on how each runner delivered their medication.
Five participants used multiple daily injections, three utilized conventional insulin pumps, and two relied on automated insulin delivery systems. The clinical protocol set a pre race glucose target of 140 to 200 mg/dL. For athletes using multiple daily injections, doctors reduced basal insulin by 25 percent. Non hybrid pump users saw a 50 percent basal reduction, while hybrid closed loop systems were set to a specific 150 mg/dL target.
During the race, athletes underwent capillary glucose checks using a glucometer at five distinct stages. These manual checks occurred at the start line, the 10 kilometer point, the 19 kilometer mark, the 30 kilometer point and the finish. Median capillary glucose started at 183.5 mg/dL and eventually dropped to 108.5 mg/dL by the finish line. Other median readings included 119.5 mg/dL at 10 kilometers, 142.5 mg/dL at 19 kilometers, and 121.5 mg/dL at 30 kilometers.
Interestingly, the study highlighted a significant accuracy gap with continuous glucose monitors during prolonged exercise. The intermittently scanned systems differed from glucometer measurements by approximately 43 percent and overestimated capillary glucose by 32.2 mg/dL. Real time continuous glucose monitors performed similarly poorly during the race. These real time systems differed by 37 percent and overestimated glucose by 50.4 mg/dL.
Hitting my forties brought a harsh reality check. The track workouts were not getting slower, but the days after them felt significantly heavier. Instead of forcing my old Tuesday and Thursday intensity schedule, I looked at the data on Masters athletes and muscle protein synthesis. I pushed my second hard session to Friday, allowing an extra forty eight hours of low intensity recovery.
My total weekly volume stayed the same, but the quality of my intervals skyrocketed. That experience reinforced a core truth about endurance training that applies directly to this new clinical data. You cannot force a generic template onto a unique biological reality. Athletes with type 1 diabetes face a much higher stakes version of this concept.
The study authors explicitly warn that marathon outcomes depend heavily on individual factors. These factors include baseline glucose control, exercise experience, and diabetes duration. It is crucial to view the study as a conceptual planning template rather than a universal race day prescription. Every runner must take this preliminary framework to their medical team to build a personal strategy.
The data from the Poznań Marathon cohort offers a valuable starting point for structuring race nutrition. The median carbohydrate intake among the runners with type 1 diabetes was 53.5 grams per hour. This translated to 2.61 grams per kilogram of body weight over the duration of the marathon. Runners must test this intake rate during long training blocks to gauge their individual tolerance and glucose response.
Proper endurance fueling also requires comprehensive contingency planning. The study noted two hypoglycemic measurements in one participant, who began the race below the recommended 140 mg/dL target. That specific runner consumed 49.5 grams of carbohydrate per hour but still experienced a dangerous dip. Athletes must carry enough reserve nutrition to address both their planned hourly intake and any unexpected downward glucose trends.
Understanding fueling myths and the reality of how carbohydrates work helps athletes build a flexible response to mid race metabolic shifts. You should never try a new fueling volume or a different carbohydrate formulation for the first time on race morning. Instead, replicate the specific pacing and nutrition strategy repeatedly during weekend long runs. This methodical approach allows you to identify exactly how your body processes fuel under sustained aerobic stress.
One of the most critical practical takeaways for veteran endurance athletes involves the reliability of continuous glucose monitors. The clinical data clearly shows that sensor readings can lag or diverge substantially during a long, strenuous effort. Because these monitoring systems overestimated glucose by up to 50.4 mg/dL, relying solely on a sensor could lead to missed warnings. Athletes should never ignore physical symptoms just because a digital device displays a reassuring number.
The researchers strongly advise carrying a traditional glucometer during longer endurance events. Athletes must maintain a pre agreed backup measurement strategy and execute a capillary check when sensor readings conflict with perceived exertion. Managing a complex metabolic condition over 42 kilometers demands reliable, objective data to guide real time decisions. Agreeing in advance on specific checkpoint actions removes the guesswork from race day.
The most important element of the entire preparation strategy is continuous medical supervision. The study authors identify insulin management as the absolute linchpin of safe marathon execution. Endurance athletes should never improvise reductions in basal or mealtime insulin based purely on a published clinical protocol. The specific 25 percent and 50 percent reductions used in the study were tailored to the exact delivery mechanisms of the participants.
Every runner must sit down with their diabetes care team to agree on an individualized glucose, carbohydrate, and insulin plan. Hydration planning follows the exact same clinical rule. The report supports a highly individualized approach to fluid intake rather than providing one universal formula. Finding practical ways to manage electrolytes, much like the guidance provided when fourfive launched their hydro electrolyte tablets, requires testing sweat rates in training.
Before attempting a marathon, runners with type 1 diabetes should also discuss their overall cardiovascular health with their doctors. Athletes with diabetes related complications or uncertain cardiovascular status must obtain appropriate medical clearance. Balancing high ambition with medical reality takes patience and a willingness to adapt. Whether you are adjusting your training week for sustainable endurance or mapping out a complex insulin strategy, success comes from respecting the data.
The athletes in the Poznań Marathon proved that careful planning and respect for the body's limits can lead to excellent competitive outcomes.
The bottom line is that marathon running with type 1 diabetes requires an individualized, medically supervised plan that prioritizes capillary glucose checks and precise insulin adjustments over generic racing advice.
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