Introduction Electronic cigarette use has grown substantially and the health effects are being closely monitored. Tracking the evolving market place and the profile of adult users is important for tobacco control efforts; however, several different ways of measuring current use have been reported. This paper examines how well a categorical definition aligns with days of use.

Methods Data from the 2018 Minnesota Adult Tobacco Survey assessed e-cigarette use based on days of use in the past month and currently using ‘every day, some days, or not at all’. Prevalence of current use and agreement of >1, >5 and >20 days of use with every day or some days were calculated.

Results The prevalence of e-cigarette use varied by category of use from 2.4% (≥20 days/30) to 6.0% (≥1 day/30). The highest prevalence was found among young adults reporting any use in the past 30 days (21.9%). Never smokers had low prevalence overall; however, 4.4% reported using in the past 30 days. Using at least 1 day in the past 30 days included a higher proportion of young adults (p<0.001) and never smokers (p<0.001) compared with other current use categories. Compared with every day or some days, the per cent agreement with days of use categories ranged from 89.7% to 94.4% and kappa ranged from 0.60 to 0.81.

Conclusions Prevalence and sociodemographics varied by definition of use. Asking ‘every day, some days or not at all’ in population-based studies has the advantage of aligning with cigarette smoking current use definition.