A medical cartridge containing multiple doses of a medical drug is disclosed. An outlet end is arranged to be connected to an injection needle for delivering the medical drug. The medical cartridge comprises a one way valve arranged in an interior part of the medical cartridge at a position near the outlet end. The one way valve allows a fluid flow from the interior of the medical cartridge towards the outlet end, but prevents a fluid flow from the outlet end towards the interior of the medical cartridge. Thereby the risk of contamination of the medical drug remaining in the cartridge is minimized.
