A medical injection system comprising an injection device and a dose limiter module, - wherein the injection device is configured for setting and injecting set doses of a drug from a reservoir and comprising a) a housing and b) a rotatable dose setting member, and wherein the injection device is configured so that: i) during dose setting, the dose setting member is rotated in a first rotational direction from a first rotational position to a second rotational position in accordance with the size of a dose to be injected, and ii) during dose injection, the dose setting member is rotated counter to said first rotational direction back to said first rotational position, - wherein the dose limiter module is adapted for being releasably coupled to the injection device to define a coupled state where the dose limiter module is attached to the injection device and to define a decoupled state where the dose limiter module is detached from the injection device, the dose limiter module comprising: - a dose limiter base, - a limiter arranged relative to the dose limiter base so that the relative position between the limiter and the dose limiter base is adjustable to set an adjusted dose limiting position, - wherein, in the coupled state, the limiter cooperates with the dose setting member to define a blocking means (260,250,240,168,268,263,253,,257,247) for preventing rotation of the dose setting member beyond the adjusted dose limiting position when the dose setting member is rotated in the first rotational direction, characterized in that the dose limiter module comprises a user operable lock (210,212,232,223,243) configured for operation between a locked state and an unlocked state to respectively prevent and enable adjustment of the position of the limiter relative to the dose limiter base, the lock (210,212,232,223,243) being configured for maintaining the lock (210,212,232,223,243) in the locked state at least when the dose limiter module is in the decoupled state. - wherein the injection device is configured for setting and injecting set doses of a drug from a reservoir and comprising a) a housing and b) a rotatable dose setting member, and wherein the injection device is configured so that: i) during dose setting, the dose setting member is rotated in a first rotational direction from a first rotational position to a second rotational position in accordance with the size of a dose to be injected, and ii) during dose injection, the dose setting member is rotated counter to said first rotational direction back to said first rotational position, - wherein the dose limiter module is adapted for being releasably coupled to the injection device to define a coupled state where the dose limiter module is attached to the injection device and to define a decoupled state where the dose limiter module is detached from the injection device, the dose limiter module comprising: - a dose limiter base, - a limiter arranged relative to the dose limiter base so that the relative position between the limiter and the dose limiter base is adjustable to set an adjusted dose limiting position, - wherein, in the coupled state, the limiter cooperates with the dose setting member to define a blocking means (260,250,240,168,268,263,253,,257,247) for preventing rotation of the dose setting member beyond the adjusted dose limiting position when the dose setting member is rotated in the first rotational direction,