A biosensor has been designed for measuring plasma fibrinogen concentrations based on an enzyme kinetic model. The values obtained correspond linearly to those of a clinical method but have a higher sensitivity within the normal range of fibrinogen. By using the disposable biosensor technology, this method is easy to follow, quick (within 2 min) and precise (with coefficients of variation to be as low as below 5%) and requires only a small amount of plasma sample (< 50 mu l). This biosensor technology also holds potential for use in point-of-care diagnostics.