¹Department of Clinical Pharmacy, Faculty of Pharmacy, Acıbadem Mehmet Ali Aydınlar University, Ataşehir 34752 İstanbul, Turkey DOI : 10.29228/jrp.473 Turkey had the highest prevalence of diabetes in Europe and approximately 60,000 people pass away because of diabetes mellitus (DM) in Turkey each year. It is essential to provide education to increase knowledge and awareness regarding DM and to motivate patients for the disease management. The aim of this study was to assess the diabetes knowledge levels of diabetes patients using insulin and to evaluate the impact of education provided by pharmacist on their diabetes knowledge level. 64.8% of the participants were having diabetes for more than 5 years and about half of the participants (51.4%) even did not know what type of diabetes they had. 64.86% of the 37 patients have never had education regarding DM or medicines used for the treatment before. The participants’ total mean score from Revised Diabetes Knowledge Test (DKT2) was significantly increased from 13.57±5.57 to 19.08±5.05 after patient education (p=0.000). Even though the number of diabetic patients is continually increasing, there is still a dearth of knowledge regarding DM in Turkey. On the other hand, the significant increase on the DKT2 score after education clearly demonstrates the effectiveness of pharmacist-driven education. Pharmacists have an impact to make important contributions on increasing patients’ awareness and knowledge regarding DM. This was a cross-sectional, pilot study conducted among diabetes mellitus patients who came to a community pharmacy in Istanbul. A structured, validated questionnaire was used to assess diabetes knowledge level and impact of patient education by pharmacist. Keywords : Diabetes mellitus; patient education; knowledge; DKT2