Objective: We aimed to determine the correlation between blood viscosity and cerebral blood flow in people acclimated to chronic hypoxia who have high blood viscosity levels. Materials and methods: A Prospective observational study was conducted in asymptomatic young adults living in Cusco (3399 m altitude). All participants were examined at low and high shear rates (75 and 300 s−1) for simulating the dynamic component of blood viscosity. A transcranial Doppler study of the middle cerebral artery was performed to measure systolic, diastolic, and mean flow velocities (FVs), as well as resistance and pulsatility indexes (PIs). Results: One hundred and thirty-one participants were included. Median viscosity levels were 5.01cP (interquartile range [IQR]: 4.45–5.73cP) at 300 s−1 and 6.16 cP (IQR: 5.58-7.20 cP) at 75 s−1, mean FV was 57 cm/s (IQR: 50–65 cm/s), and the PI was 0.91 (0....