Diabetes Mellitus and Long-Distance Running: A Systematic Review.

Background Athletes with diabetes increasingly participate in endurance running, benefiting from physiological adaptations and technological advances like continuous glucose monitoring (CGM) for glycemic control. So far, no comprehensive review summarizing the current knowledge has been performed.Objective To identify the prevalence of long-distance runners with diabetes, their performance, methods used for blood glucose monitoring and glycemic control.Methods PubMed, Medline Ovid, Scopus, SPORTDiscus, Cochrane databases, CINAHL, and Web of Science were systematically searched until April 2024 using key terms related to long-distance running and diabetes. An updated search applying the identical strategy was conducted on May 3rd, 2026, to capture subsequently published literature. This study included original research articles, case reports, and case studies published in English or German in peer-reviewed journals, utilizing both quantitative and qualitative methodologies. Eligibility criteria encompassed runners with a confirmed diagnosis of diabetes mellitus, irrespective of type, who participated in endurance events of at least half-marathon distance, including half-marathons, marathons, ultra-marathons, and other ultra-endurance competitions. Patients with prediabetic state, gestational diabetes, or after pancreatic islet-cell transplantation were excluded. For quality assessment, we used the Joanna Briggs Institute of Analytical Cross-Sectional Studies or the Joanna Briggs Institute of Analytical Case Report critical appraisal tool.Results A total of 656 studies were identified, with 22 meeting the inclusion criteria, comprising 99 runners with diabetes (99.0% Type 1, 1.0% Type 2 diabetes mellitus). Among them, 50.0% used CGM, 27.2% had an insulin pump, 63.6% administered insulin via multiple daily injections, and the method of insulin application was not specified in 7.0% of runners. The weighted mean HbA1c was 7.4% (95% CI 6.9-8.1). Time-in-range varied by race distance: 40-100% for half-marathoners, 51.6% for marathoners, and 47-73% for ultra-marathoners. No cases of symptomatic hypoglycemia were observed during the races. However, asymptomatic late-onset hypoglycemia (occurring 6-15 h post-exercise) was reported in 27 runners. The most common insulin adjustment strategy before competitive races was a 50-80% reduction of basal insulin.Conclusion Despite limited research, evidence suggests that with proper preparation and multidisciplinary support, athletes with diabetes can safely participate in endurance events, including ultra-marathons, while maintaining stable glycemic control.Trial Registration PROSPERO-CRD42024539281.