BackgroundTreatment plans fail if patients have poor medication adherence. Our aim was to compare medication adherence, reasons for non-adherence, and satisfaction with community support among type 2 diabetes mellitus patients who pay for their medications and those who receive it free.MethodsA descriptive cross-sectional study was conducted at Anuradhapura, Sri Lanka, among patients who were on oral anti-diabetic drugs for at least 3 months. They were grouped into two: universal-free group and fee-paying group. Three different scales were used to score medication adherence, reasons for non-adherence, and satisfaction with community support. Fisher’s exact test was performed to determine if there was a significant difference between the two groups (p < 0.05) concerning medication adherence and satisfaction with community support.ResultsThe median (IQR) medication adherence scores for fee-paying group and universal-free group were 3 (2-3) and 3 (3-3), respectively; the median (IQR) scores for satisfaction with community support were 5 (2–6) and 4 (4–6), respectively. Both the adherence and the satisfaction failed to show a significant difference between the two groups. Forgetfulness, being away from home, complex drug regime, and willingness to avoid side effects were common reasons of non-adherence for both the groups.ConclusionsThere was no significant difference in medication adherence between the universal-free group and fee-paying group, despite of having a significantly different income. The universal-free health service would be a probable reason.Electronic supplementary materialThe online version of this article (10.1186/s41043-019-0161-9) contains supplementary material, which is available to authorized users.