When a lesion occurs in a blood vessel, a series of mechanisms are activated to stop hemorrhage by increasing blood viscosity at the wounded place. If a sample of blood extracted of the human body is illuminated with coherent light, a time varying speckle pattern is observed. It is show high activity at the start and decreases with time until it finally stop. The analysis of these patterns shows a degree of correlation between speckle activity and the temporal evolution of the clot. These preliminary results are promising for the continuation of studies aiming to the application of biospeckle techniques to the analysis of coagulation times.