BACKGROUND: The transradial approach (TRA) is preferred for coronary procedures due to improved outcomes and lower complication rates. However, complications such as radial artery stenosis (RAS) and occlusion (RAO) post TRA require investigation. This study aimed to explore the link between whole blood viscosity (WBV) and RAS/RAO after TRA coronary angiography. METHODS: A retrospective analysis of 215 TRA coronary angiography patients was conducted. Doppler ultrasonography assessed RAS/RAO one month post procedure. WBV, calculated from haematocrit and total plasma protein (TP), was evaluated at low (LSR) and high shear rates (HSR). RESULTS: RAS/RAO incidence was 15.3%, with 7.4% of patients experiencing RAO. Patients with RAS/RAO showed significantly elevated HSR, LSR and TP levels, with lower blood urea nitrogen levels. Multivariable analysis identified body mass index, HSR and LSR as independent RAS/RAO predictors. CONCLUSIONS: This study established WBV association with RAS/RAO after TRA, suggesting WBV as a potential predictor and aiding pre-TRA risk assessment for alternative angiography routes.