BackgroundIn 2004, Ghana started experimenting a National Health Insurance Scheme (NHIS) to reduce out-of-pocket payment for healthcare. Like many other social health insurance schemes in Africa, the NHIS is striving for universal health coverage (UHC). This paper examines trends and characteristics of enrolment in the scheme to inform policy decisions on attainment of UHC.MethodsWe conducted trend analysis of longitudinal enrolment data of the NHIS for the period, 2010–2017. Descriptive statistics were used to examine trends and characteristics of enrolment by geographical region and member groups.ResultsOver the 8-year period, the population enrolled in the scheme increased from 33% (8.2 million) to 41% (11.3 million) between 2010 and 2015 and dropped to 35% (10.3 million) in 2017. Members who renewed their membership increased from 44% to 75.4% between 2010 and 2013 and then dropped to 73% in 2017. On average, the urban regions had significantly higher number of new enrolments than the rural ones. Similarly, the urban and peri-urban regions recorded significantly higher number of renewals than the other regions. In addition, persons below the age of 18 years and the informal sector workers had significantly higher number of enrolment than any other member group.ConclusionsEnrolment in the NHIS is declining and there are significant differences among geographical regions and member groups. Managers of the NHIS need to enforce the mandatory enrolment provision in the Act governing the scheme, employ innovative strategies such as mobile phone application for registration and renewals and address delays in healthcare provider claims to improve enrolment.Electronic supplementary materialThe online version of this article (10.1186/s41256-018-0087-6) contains supplementary material, which is available to authorized users.