Our patient was a Caucasian man with long-lasting type 1 diabetes (age 31 years, body mass index 23.8 kg m−2, C-peptide 0.00 nmol L−1, glycosylated hemoglobin A1c 60 mmol mol−1 [7.6%], diabetes duration 24 years) was switched to insulin degludec (Tresiba®; Novo Nordisk, Bagsvaerd, Denmark) for study purposes (once-daily injection, 19 U/day in the evening) [4]. Here, INS is linked to type 1 diabetes mellitus.