Aims:
This study re-analysed data from the HypoDE trial to assess the prevalence of nocturnal hypoglycaemia, evaluate the impact of continuous glucose monitoring (CGM) on nocturnal and daytime hypoglycaemia, and explore their influence on severe hypoglycaemia (SH).

Methods:
The HypoDE trial was a randomized controlled trial involving 141 adults with type 1 diabetes, impaired hypoglycaemia awareness, or prior SH. Participants were randomized to CGM (Dexcom G5) or self-monitoring of blood glucose (control). Outcomes included the percentage of time spent in hypoglycaemia (<3.9 mmol/L, <3.0 mmol/L), episode duration, and SH incidence.

Results:
At baseline, nocturnal hypoglycaemia (<3.0 mmol/L) exposure exceeded daytime by 1.4 percentage points (95 % CI 0.6–2.2; p < 0.002), with episodes lasting 30.7 min longer (CI 21.5–39.9). Using CGM, these differences disappeared (<3.0 mmol/L: 0.3 percentage points, CI 0.7–1.3), while they persisted in the control group. Daytime hypoglycaemia significantly increased SH risk (IRR 1.10 per percentage point, CI 1.01–1.21; IRR 1.04 per minute, CI 1.01–1.07).

Conclusions:
CGM effectively reduced nocturnal and daytime hypoglycaemia. Without CGM, nocturnal hypoglycaemia contributes to daytime risks, while daytime hypoglycaemia elevates SH risk. Expanding CGM access and addressing nocturnal hypoglycaemia in resource-limited settings are critical.

Trial registrationClinicaltrials.gov: NCT02671968.