The present invention provides a fluorogenic composition for assaying complement activation that comprises a substrate for C3 convertase that is linked to a first fluorophore and a second fluorophore, wherein the fluorescence of the first and second fluorophores are mutually substantially quenched when the two fluorophores are present at a distance less than the characteristic distance for the two fluorophores. In one embodiment, the fluorescence of the first fluorophore is substantially quenched by the second fluorophore, and the second fluorophore emits heat upon quenching. The present invention also provides a method for assaying complement activation, wherein the method includes the steps of incubating a biological sample with a polymer to provide a polymeric biological sample, followed by incubating the polymeric biological sample with the fluorogenic composition, and measuring the fluorescence. The method may optionally include the step of measuring the optical properties of the biological sample prior to the incubation steps. The present invention further provides a kit for assaying complement activation that comprises the fluorogenic composition disclosed herein.