A microfluidic passive device and method for determining clotting time are described, of a fluid medium such as blood, of low production cost which can therefore be disposable. When optimised to determine blood clotting time, it requires a minimal whole blood sample (<；15 µL) and it is particularly suited to INR or PT determination, which can be used autonomously by patient without venipuncture. Monitoring, and processing means to interpret the results are comprised in an external device. A production method for the fabrication of the microfluidic device is also provided.
