The invention relates to a method for indirectly determining the blood-clotting status. The inventive method comprises the following steps: a) collecting body fluids which contain a protein that can be modified by a vitamin K-dependent .gamma.-carboxylase, b) determining at least two concentrations selected from a group consisting of a first concentration C1 of carboxylated protein, a second concentration C3 of decarboxylated protein and an entire concentration C3 of carboxylated and decarboxylated protein, whereby the first concentration C1 is determined using a first antibody A1, the second concentration using a second antibody A2 and the third concentration C3 using a third antibody A3, c) generating a first quotient Q1 from the first C1 and second C2 concentration or generating a second quotient Q2 from the third C3 and first C1 concentration or generating a third quotient Q3 from the third C3 and second concentration C2, whereby a concentration C1, C2, C3 which has not been determined in step b) and which is required for generating the first Q1, the second Q2, or the third quotient Q3 is calculated according to the following relation: C3-C2=C1 and d) the first, second or third quotient Q1, Q2, Q3 are correlated with the blood-clotting status.