Adults with type 1 diabetes (T1D) have an elevated risk for cardiovascular disease (CVD) compared with the general population. HbA1c is the primary modifiable risk factor for CVD in T1D. Fewer than 1% of patients achieve euglycemia (<5.7%HbA1c). Ketogenic diets (KD; ≤50g carbohydrate/day) may improve glycemia and downstream vascular dysfunction in T1D by reducing HbA1c and insulin load. However, there are concerns regarding the long-term CVD risk from a KD. Therefore, we compared data collected in a 60-day window in an adult with T1D on exogenous insulin who consumed a KD for 10 years versus normative values in those with T1D (T1D norms). The participant achieved euglycemia with an HbA1c of 5.5%, mean glucose of 98[5]mg/dL(median[IQR]), and 90[11]%time-in-range 70-180mg/dL (T1D norms: 1st percentile for all); and low insulin requirements of 0.38±0.03IU/kg/day (T1D norms: 8th percentile). Seated systolic blood pressure (SBP) was 113mmHg (T1D norms: 18th percentile) while ambulatory awak