To investigate the usability of leuko-glycemic index (LGI) at chronic coronary syndromes (CCS) class 1 for determining the extent and severity of coronary artery disease (CAD). An observational study. Department of Cardiology, University of Pamukkale University Hospital, Turkey, between September 2021 and January 2022. One hundred and thirty-four patients, whose myocardial perfusion scintigraphy (MPS) was requested due to CCS class 1, and on whom a coronary angiogram (CAG) was performed due to evidence of ischemia, were analysed. Blood samples were taken from the patients during their hospitalisation before CAG. LGI was calculated as mg/dl.mm3 by multiplying both values and dividing by a thousand. The patients were analysed in two groups according to the critical stenosis and non-critical stenosis detected in the coronary arteries. The LGI was recorded as 480 mg/dl.mm3 (407-603) vs. 572 mg/dl.mm3 (433-877), p=0.006, and the Gensini score (6 (3-10) vs 40 (23-60), p<0.001) was significantly higher in the critical CAD group. A significant relationship has detected the increase in LGI and the extensity and severity of CAD (Unadjusted; OR (95% CI); 1.003 (1.001 - 1.004) p=0.002, adjusted; OR (95% CI); 1.002 (1.001 - 1.004) p=0.004). A high LGI was a predictor of CAD severity among CCS class 1 patients and was found to correlate with the Gensini score. The use of this simple and inexpensive index, together with other non-invasive tests before CAG, may provide some knowledge about the severity of CAD. Coronary artery disease, Leukocyte glucose index, Myocardial perfusion scintigraphy.