A method of 
factor XI-dependent blood coagulation enhancement in a subject in need of enhanced blood coagulation comprising administering a therapeutically effective amount of a composition comprising a non-
anticoagulant sulfated 
polysaccharide (NASP) to the subject. A method of 
factor XI-dependent blood coagulation enhancement in a subject in need of enhanced blood coagulation comprising: (i) selecting a subject that is not deficient for 
factor XI; and (ii) administering a therapeutically effective amount of a composition comprising a non-
anticoagulant sulfated 
polysaccharide (NASP) to the subject, wherein the NASP enhances blood coagulation in a factor XI-
dependent manner. A method of identifying a non-
anticoagulant sulfated 
polysaccharide (NASP) which is capable of enhancing blood coagulation in dependence on FXI, the method comprising: a) combining a blood or 
plasma sample comprising activation competent FXI with a composition comprising a sulfated polysaccharide and measuring the clotting or 
thrombin generation parameters of the blood or 
plasma sample; b) combining a corresponding blood or 
plasma sample deficient in activation competent FXI with a composition comprising the sulfated polysaccharide and measuring the clotting or 
thrombin generation parameters of the blood or 
plasma sample; and c) comparing the clotting or 
thrombin generation parameters of the blood or 
plasma samples as determined in steps (a) and (b) with each other, wherein a decrease in the 
clotting time of the blood sample or an increase in peak thrombin or decrease in peak time of the 
plasma sample comprising activation competent FXI compared to the 
clotting time of the blood sample or peak thrombin or peak time of the 
plasma sample deficient in activation competent FXI is indicative of a NASP which is capable of enhancing blood coagulation in dependence on FXI.