Objective: To study the sensitivity and specificity of IDRS in diagnosing glucose intolerance and DM amongst first degree relatives of patients with Type 2 Diabetes Mellitus (T2DM). Methods: 120 healthy first degree relatives of patients with T2DM, aged 18 years and above, were invited to participate in the study after a written consent. IDRS includes : age, waist circumference, family history of diabetes and physical activity. The individuals are classified as having high risk (score ≥ 60), moderate risk (score 30-50) and low risk (score < 30) out of a total score of 100. The IDRS was calculated and subjects were advised to come after an overnight fast for an Oral Glucose Tolerance Test (OGTT). Patient’s were then categorized as having Normal Glucose Tolerance (NGT : FBS < 100 mg/dl and PLBS <140 mg/dl), Impaired Fasting Glucose (IFG : FBS ≥ 100 and <126 mg/dl), Impaired Glucose Tolerance (IGT : PLBS ≥ 140 and < 200 mg/dl ) or Diabetes Mellitus (FBS ≥ 126 and/or PLBS ≥ 200 mg/dl) as per the ADA criteria. Results: There were a total of 62 males and 58 female subjects. Following the OGTT, 48(40%) subjects were found to have NGT. DM was diagnosed in 25 (20.8%) subjects all of whom had IDRS ≥ 60 giving a sensitivity of 100% and specificity of 28.4%; 13(10.8%) subjects had FBS ≥ 126 mg/dl, 22 (18.3%) had PLBS ≥ 200 mg/dl and 10 (8.3%) subjects had both values abnormal. IFG was diagnosed in 44 (36.7%) subjects and IGT in 30 (25%) subjects. IFG and IGT was present in 16 (13.3%) subjects. When the 64 (68.8%) subjects having glucose intolerance and IDRS ≥ 60 were analyzed, the sensitivity was found to be 88.9% and the specificity 39.6%. Conclusion: IDRS is a good tool to apply on first degree relatives of patients with T2DM for the diagnosis of glucose intolerance and DM.