Adherence to pharmacological therapies are keys to effective treatments in diabetic patients. Previous reviews found that most adherence measurement studies on chronic diseases used a self-reported scale. However, there is no consensus on the best scale to measure adherence in diabetic patients. The purpose of this systematic review was to identify the potential self-reported scale that could be considered for measuring medication adherence in diabetic patients and to provide recommendations for researchers or clinicians to determine appropriate adherence self-reported scales in diabetic patients. This review follows general guidelines in the implementation of systematic reviews. After further review, it was found that 33 studies met all inclusion criteria from 4 databases (Wiley, Science Direct, Scopus, and PubMed). The articles were done by the PRISMA, while the keywords were determined by the PICO method. Most research was conducted in Asia (69.7%) and America (18.2%) on patients with type 2 diabetes (81.3%), patients in hospitals (54.5%), suffering for 1–6 months (54.5%), and using a cross-sectional study design (78.8%). HbA1c clinic data (57.6%) were used in most studies as biological markers of adherence. The measurement scales of medication adherence in diabetic patients are MMAS-8 (57,.5%), MMAS-4 (12.1%), BMQ (9%), MCQ (6%), ARMS (3%), ARMS-D (3%), GMAS (3%), LMAS-14 (3%), and MARS-5 (3%). This review provides information on the different self-reported scales most widely used in diabetic medication adherence research. Various aspects need to be considered before choosing the scale of adherence.