535-P: The Effect of Starting Blood Glucose Levels on Electrolyte Balance During and After Exercise in Type 1 Diabetes

ADA guidelines recommend that people with type 1 diabetes (PWT1D) start exercise with blood glucose (BG) levels of 7-mmol/L. Those fearing hypoglycemia often start higher, which may affect kidney function and electrolyte balance. We examined serum and urine electrolyte concentration during aerobic exercise (cycling 45 min at 60%VO₂peak) in PWT1D (10F/2M, mean±SD: age 29±7 years, VO₂peak 37.8±7.6 mL/kg/min, A_1C 7.6±0.8%) and age, sex, and fitness-matched controls. Control participants (CON) completed a single exercise session with BG in normal physiological range, while PWT1D completed two sessions with different starting BG levels: 8-mmol/l (MOD) , and 12-14 mmol/l (HI) .

Urine specific gravity, glucose and potassium were higher during exercise and recovery in MOD when compared to CON (effect of treatment p<0.05) , with only urine glucose being higher in HI when compared to MOD (effect of treatment p<0.05) . Serum sodium, potassium, magnesium, and calcium increased from pre to post exercise in all sessions, with sodium being higher, and magnesium and calcium being lower in MOD versus CON (effect of treatment p<0.05) . There was no difference in these electrolytes between MOD and HI sessions (effect of treatment p>0.05) in PWT1D. Serum glucose decreased during exercise in MOD and HI sessions (effect of time p<0.05) , with serum glucose being higher during the HI session (effect of treatment p<0.05) . The lack of significant differences in electrolytes between MOD and HI sessions suggests that exercise with higher BG levels does not pose immediate risk during exercise of moderate intensity and duration. Further studies should examine the impact of hyperglycemia on electrolyte balance during longer or more intense exercise sessions.