An apparatus and method for irradiation of fluid with electromagnetic radiation, and in particular to an apparatus and method for irradiation of blood or other body fluids with ultraviolet radiation is provided. The apparatus (1) comprises a housing (2) having disposed therein at least one mount (6) adapted for receiving an ultraviolet radiation source (7) and at least one holder (8) adapted for receiving a container of the fluid. The housing (2) is adapted for operability between a first position, wherein the container (9) may be placed in the holder (8) and a second position, wherein the housing (2) may form a capsule. The apparatus further comprises a control assembly for powering the ultraviolet radiation source (7). At least a portion of the inner surface of the housing (2) is capable of reflecting the ultraviolet radiation.