AIM – To show association between elevated Glycated Haemoglobin levels and its effect on pulmonary function test. INTRODUCTION Diabetes mellitus is a syndrome of hyperglycemia leading to micro as well as macrovascular complications. Diabetes is not directly interlinked with any specific pulmonary symptoms and hence periodic screening for lung disease is not done in diabetic patients. However an extensive micro-vascular circulation and an abundant connective tissue in the lung raise the possibility that the lung may also be a ‟target organ‟ in diabetic patients. MATERIALS AND METHOD-. 50 patients of both Type 1 and type 2 DM of the age group 20–70 years taking anti diabetic medications were randomly selected. Controls includes 50 non-diabetic apparently healthy individuals. RESULTS-The mean age for all cases was 45.84 ± 15.40 years. The percentage of the male and female in both the groups were 60% (30) and 40% (20) respectively. Out of 50 diabetes patients, 34 were diagnosed for 5 -10 years and 16 were diagnosed for >10 year. 2 were Type 1 DM and 48 were Type 2 DM. 3 cases were with well controlled diabetes (HbA1c ≤ 7) whereas 47 cases were having uncontrolled diabetes (HbA1c >7). The mean HbA1c was 9.75 ± 2.62. CONCLUSION- DM being a systemic disease, also affects lungs causing both restrictive and obstructive type of ventilatory changes probably because of glycosylation of connective tissues, reduced pulmonary elastic recoil, and inflammatory changes . So, we may conclude that patients with diabetes mellitus have underlying pulmonary dysfunction