OBJECTIVES: Hypoglycaemic events are proven to have a negative impact on the health-related quality of life (HRQoL) of patients with diabetes. The negative impact of hypoglycaemia on HRQoL may be evaluated via disutility scores. The aim of this study was to assess the marginal impact of non-severe hypoglycaemic events on HRQoL and to investigate the functional form of the disutility of hypoglycaemic events. METHODS: Published disutility values from a large-scale, web-based time-trade-off study (TTO) conducted in UK, USA, Canada, Germany and Sweden with 8,286 respondents, were used as a basis for the analysis of non-severe daytime and nocturnal hypoglycaemia. Non-linear regression curves were fitted to the total disutility of different frequencies of hypoglycaemic events. A weighting scheme was used to allow each data point (one event quarterly, one monthly, one weekly or three weekly) to reflect the range of hypoglycaemic frequencies the data point represented. Non-parametric bootstrapping was applied to characterise the uncertainty of the marginal disutility. RESULTS: Power function regression curves were estimated at Ud=0.0141x0.3393 and Ud=0.0221x0.3277, where Ud is disutility and x is the annual hypoglycaemic event rate, for non-severe daytime and non-severe nocturnal events. An increase from 0 to 1 hypoglycaemic events per year, produced a utility decrease of 0.0141 for non-severe daytime, and 0.0221 for non-severe nocturnal, whereas an increase of one hypoglycaemic event per year for a patient who experiences 25 hypoglycaemic events per year produces a marginal impact of 0.0006 and 0.0008 for non-severe daytime and non-severe nocturnal, respectively. CONCLUSIONS: If patient-level data are available, non-linear functions estimated with TTO data might improve the precision of the measured impact of hypoglycaemic events. The results seen here illustrate diminishing marginal disutility with increasing numbers of hypoglycaemic events. This fits with the phenomenon of “first being worst” with regards to hypoglycaemia.