The invention relates to an apparatus for self treatment of diabetes. The apparatus is particularly advantageous by comprising a plurality of devices each of which has its own dedicated function corresponding to a number of acts which a diabetic must perform on himself. The individual devices are mutually interconnectible, and the combination comprises at least a body fluid analyser and a dosing apparatus for administering a predetermined dose of insulin to the patient. Each of the devices may be provided in several sizes so that the user himself may combine the relevant devices of the relevant size with respect to the current need. This reduces the risk of forgetting parts of the equipment, and the confidence of using the equipment is enhanced because it is evident to the user that it is a complete apparatus consisting of unified parts.