Adolescence is associated with high-risk hyperglycemia. This study examines the phenomenon in a life course context.


A total of 93,125 people with type 1 diabetes aged 5 to 30 years were identified from the National Diabetes Audit and/or the National Paediatric Diabetes Audit for England and Wales for 2017/2018–2019/2020. For each audit year, the latest HbA1c and hospital admissions for diabetic ketoacidosis (DKA) were identified. Data were analyzed in sequential cohorts by year of age.


In childhood, unreported HbA1c measurement is uncommon; however, for 19-year-olds, it increases to 22.3% for men and 17.3% for women, and then reduces to 17.9% and 13.1%, respectively, for 30-year-olds. Median HbA1c for 9-year-olds is 7.6% (60 mmol/mol) (interquartile range 7.1–8.4%, 54–68 mmol/mol) in boys and 7.7% (61 mmol/mol) (8.0–8.4%, 64–68 mmol/mol) in girls, increasing to 8.7% (72 mmol/mol) (7.5–10.3%, 59–89 mmol/mol) and 8.9% (74 mmol/mol) (7.7–10.6%, 61–92 mmol/mol), respectively, for 19-year-olds before falling to 8.4% (68 mmol/mol) (7.4–9.7%, 57–83 mmol/mol) and 8.2% (66 mmol/mol) (7.3–9.7%, 56–82 mmol/mol), respectively, for 30-year-olds. Annual hospitalization for DKA rose steadily in age from 6 years (2.0% for boys, 1.4% for girls) and peaked at 19 years for men (7.9%) and 18 years for women (12.7%), reducing to 4.3% for men and 5.4% for women at age 30 years. For all ages over 9 years, the prevalence of DKA was higher in female individuals.


HbA1c and the prevalence of DKA increase through adolescence and then decline. Measurement of HbA1c, a marker of clinical review, falls abruptly in the late teenage years. Age-appropriate services are needed to overcome these issues.

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