The present invention relates to a device for separation of plasma or serum from a blood sample from a small blood volume (e.g. capillary blood). The device comprises a separation member, an extraction member and a housing. The extraction member comprises a base and one or more microstructures protruding from and being integrally formed with said base, wherein said one or more microstructures are configured to extract plasma or serum from said separation member by capillary forces. The present invention further provides methods for separating plasma or serum using the device according to the present invention. Similarly, also methods for analyzing one or more proteins and/or metabolites contained in plasma or serum that is separated using a device according to the present invention are provided.