The prevalence of diabetes is constantly growing and an ever increasing number of diabetics travel to moderate (1500-2000 m, 5000-6500 ft.) or high altitude (>2500 m, >8000 ft) for recreational purposes. Stays at moderate altitude are very well tolerated for a majority of diabetics, but can be limited by hypoxia or equipment failure due to freezing temperatures, or by the occurence of altitude-specific pathologies, as acute mountain sickness, which can mimick hypoglycemia in the diabetic. Beyond 2500 m, freezing, remoteness, hypoxia-induced anorexia, side effects of medications and the higher incidence of mountain sickness can make diabetes control difficult. A well informed and prepared diabetic patient, with sufficient and adequatly kept equipment, and a reasonably good fitness level, can enjoy and master mountaineering.