Objective: To investigate rates and risk factors of hospital admission for diabetic ketoacidosis (DKA) or severe hypoglycemia in young patients with established type 1 diabetes. Design: In total, 31 330 patients with type 1 diabetes (median age 12.7 years) from the Diabetes Patienten Verlaufsdokumentation (DPV) Prospective Diabetes Registry treated between 2011 and 2013 in Germany were included. Methods: Admission rates for DKA (pH !7.3 or bicarbonate !15 mmol/l) and severe hypoglycemia (requiring assistance from another person) were calculated by negative binomial regression analysis. Associations of DKA or hypoglycemia with patient and treatment characteristics were assessed by multivariable regression analysis. Results: The mean admission rate for DKA was 4.81/100 patient-years (95% CI, 4.51-5.14). The highest DKA rates were observed in patients with HbA1c R9.0% (15.83 (14.44-17.36)), age 15-20 years (6.21 (5.61-6.88)) and diabetes duration of 2-4.9 years (5.60 (5.00-6.27)). DKA rate was higher in girls than in boys (5.35 (4.88-5.86) vs 4.34 (3.95-4.77), PZ0.002), and more frequent in migrants than in non-migrants (5.65 (4.92-6.49) vs 4.57 (4.23-4.93), PZ0.008). The mean admission rate for severe hypoglycemia was 1.45/100 patient-years (1.30-1.61). Rates were higher in migrants compared to non-migrants (2.13 (1.72-2.65) vs 1.28 (1.12-1.47), P!0.001), and highest in individuals with severe hypoglycemia within the preceding year (17.69 (15.63-20.03) vs patients without preceding hypoglycemia 0.42 (0.35-0.52), P!0.001). Differences remained significant after multivariable adjustment. Conclusions: The identification of at-risk individuals for DKA (patients with high HbA1c, longer diabetes duration, adolescents, girls) and for severe hypoglycemia (patients with preceding severe hypoglycemia, migrants) may facilitate targeted diabetes counselling in order to prevent these complications.