AbstractAimsAmong adults with insulin‐ and/or secretagogue‐treated diabetes in the United States, very little is known about the real‐world descriptive epidemiology of iatrogenic severe (level 3) hypoglycaemia. Addressing this gap, we collected primary, longitudinal data to quantify the absolute frequency of events as well as incidence rates and proportions.Materials and MethodsiNPHORM is a US‐wide, 12‐month ambidirectional panel survey (2020‐2021). Adults with type 1 diabetes mellitus (T1DM) or insulin‐ and/or secretagogue‐treated type 2 diabetes mellitus (T2DM) were recruited from a probability‐based internet panel. Participants completing ≥1 follow‐up questionnaire(s) were analysed.ResultsAmong 978 respondents [T1DM 17%; mean age 51 (SD 14.3) years; male: 49.6%], 63% of level 3 events were treated outside the health care system (e.g. by family/friend/colleague), and <5% required hospitalization. Following the 12‐month prospective period, one‐third of individuals reported ≥1 event(s) [T1DM 44.2% (95% CI 36.8%‐51.8%); T2DM 30.8% (95% CI 28.7%‐35.1%), p = .0404, α = 0.0007]; and the incidence rate was 5.01 (95% CI 4.15‐6.05) events per person‐year (EPPY) [T1DM 3.57 (95% CI 2.49‐5.11) EPPY; T2DM 5.29 (95% CI 4.26‐6.57) EPPY, p = .1352, α = 0.0007]. Level 3 hypoglycaemia requiring non‐transport emergency medical services was more common in T2DM than T1DM (p < .0001, α = 0.0016). In total, >90% of events were experienced by <15% of participants.ConclusionsiNPHORM is one of the first long‐term, prospective US‐based investigations on level 3 hypoglycaemia epidemiology. Our results underscore the importance of participant‐reported data to ascertain its burden. Events were alarmingly frequent, irrespective of diabetes type, and concentrated in a small subsample.