A checkweigher (10) for measuring the weight of a pre-metered dose of medicament in a pharmaceutical blister (12) is provided. The checkweigher comprises a rotatable blister support element (14) for supporting a plurality of blisters (12), an evacuation assembly (16) for sequentially accessing and removing the contents of the plurality of blisters (12) as the blister support element rotates, a load sensor (18) for weighing the blister support element (14) and the plurality of blisters (12), drive means (20) for moving the blister support element (14) to and from the load sensor (18), and a controller (22) for controlling the drive means (20). The plurality of blisters (12) may be provided as single blister units or as part of a blister pack.