Objectives: Since no studies have been published on how active smoking affects switching to insulin therapy, we aimed to investigate the role of smoking on switching to insulin therapy in type 2 diabetes mellitus patients.

Methods: A total of 617 type 2 diabetes mellitus patients, who started insulin treatment due to the inability to achieve glycemic control with maximum oral anti-diabetic treatment, were included in the study. The patients were divided into three groups according to their smoking status at the beginning of insulin therapy: smokers (n=143), ex-smokers (n=189), and non-smokers (n=285). Demographic and metabolic data, treatment regimens, and insulin start times were evaluated.

Results: The age of onset of diabetes was lower in smokers than non-smokers. Non-smoker duration of diabetes (p=0.001) and switching to insulin treatment (p<0.001) were statistically higher than smokers. HbA1c values of non-smokers were statistically similar to the other two groups.

Conclusions: Diabetes onset age and switching to insulin therapy is shorter in smokers than in non-smokers. These results reveal that glycemic control is impaired with smoking and patients have to switch to insulin treatment in a shorter time. Smoking cessation programs should also be offered to the diabetic population.

Keywords: Smoking, Type 2 Diabetes Mellitus, Diabetic Complications, Insulin Treatment, HbA1c.