Blood Glucose and Altitude
I am 72 years old and have had diabetes for 15 years. At sea level in Southern California, with a moderate activity level and normal eating habits, I need between 140 and 150 units of Humalog each day. When I exercise, my blood sugars rise, and I need insulin to come back down. I keep my blood glucose in check by measuring 4 to 6 times per day, and I use both a needle and a pump. I control to between 70 and 110 and have an A1C of 6.2. I currently live in Aspen/Snowmass, Colo., at an altitude of 8,200 feet. Although I do exercise more, my insulin requirement is between 40 and 50 units each day. In addition, when I exercise, my blood sugars drop, so I can only ski or bike starting at an elevated blood sugar level. Quite the opposite from sea level. The dawn phenomenon that I experience requires me to take an additional 15 units of insulin at sea level, but only an additional 6 units when I am at a higher altitude. I have not found an explanation yet for this phenomenon. William McArthur, Aspen/Snowmass, Colorado
Henry Rodriguez, MD, responds: It sounds like the increase in exercise that you engage in when at a higher altitude in Colorado is the major factor causing the decrease in your insulin requirement. In children's diabetes camps I've seen that a cut of 20 to sometimes 50 percent of kids' normal insulin allotment is required to address the physical activity of camp, depending on the child's baseline activity. And where I'm located in Indiana, altitude is definitely not a factor!
However, at a higher altitude, combined with the element of increased exercise, the heart rate is higher and insulin may be absorbed more rapidly. My colleague, H. Peter Chase, MD, Professor of Pediatrics at the Barbara Davis Center for Childhood Diabetes at the University of Colorado, assists in a pediatric diabetes camp located in Colorado at an altitude of about 8,500 feet. He has observed similar effects in the children who attend. The medical staff has to decrease everyone's insulin dosages by 20 percent. Again, this is largely due to the children's increased activity level. Over time, we would expect the effect of altitude to dissipate.