Device for obtaining cell-free and sterile serum made from whole blood, wherein the device comprises: - a blood bag for holding whole blood and for coagulating the whole blood into a solid portion containing the cell components of the blood and into a fluid containing serum, wherein the blood bag has an outlet for discharging the fluid from the blood bag; - a filter module with a fluid connection to the blood bag by means of the outlet of the blood bag; wherein - the blood bag has a barrier in the area of the outlet, which barrier is suitable for retaining at least a large part of the solid portion and for enabling the fluid to flow through; - the filter module has a housing with an interior and an inner wall bordering the interior in which a semi-permeable membrane suitable for retaining solid portions contained in the fluid is arranged, which membrane subdivides the interior into a retentate space and a permeate space; - wherein the semi-permeable membrane of the filter module is a bundle of hollow-fiber membranes and the retentate space is formed by the lumens of the hollow-fiber membranes and the permeate space is formed by the outer space bordering the inner wall of the housing and surrounding the hollow-fiber membranes; - wherein the semi-permeable membrane enables a separation of the fluid discharged from the blood bag into serum as a permeate and into retentate, in which particular components potentially contained in the fluid are retained, and has a transmembrane flow in a range of from 15,000 to 30,000 L/(m 2 ·h·bar), as well as a nominal pore size of 0.2 μm; and - wherein the filter module has an inlet device for introducing the fluid discharged from the blood bag into the retentate space and a permeate outlet for discharging the serum from the permeate space; as well as - at least one collection container for serum which has an inlet opening, wherein the permeate outlet of the filter module and the inlet opening of the at least one collection container are connected by means of a connection line; - a blood bag for holding whole blood and for coagulating the whole blood into a solid portion containing the cell components of the blood and into a fluid containing serum, wherein the blood bag has an outlet for discharging the fluid from the blood bag; - a filter module with a fluid connection to the blood bag by means of the outlet of the blood bag; wherein - the blood bag has a barrier in the area of the outlet, which barrier is suitable for retaining at least a large part of the solid portion and for enabling the fluid to flow through; - the filter module has a housing with an interior and an inner wall bordering the interior in which a semi-permeable membrane suitable for retaining solid portions contained in the fluid is arranged, which membrane subdivides the interior into a retentate space and a permeate space; - wherein the semi-permeable membrane of the filter module is a bundle of hollow-fiber membranes and the retentate space is formed by the lumens of the hollow-fiber membranes and the permeate space is formed by the outer space bordering the inner wall of the housing and surrounding the hollow-fiber membranes; - wherein the semi-permeable membrane enables a separation of the fluid discharged from the blood bag into serum as a permeate and into retentate, in which particular components potentially contained in the fluid are retained, and has a transmembrane flow in a range of from 15,000 to 30,000 L/(m 2 ·h·bar), as well as a nominal pore size of 0.2 μm; and - wherein the filter module has an inlet device for introducing the fluid discharged from the blood bag into the retentate space and a permeate outlet for discharging the serum from the permeate space; as well as - at least one collection container for serum which has an inlet opening, wherein the permeate outlet of the filter module and the inlet opening of the at least one collection container are connected by means of a connection line;