A treatment injury is the most typical compensable injury. A compensable treatment injury is a bodily injury which was caused by an examination, treatment or other similar action performed on the patient, or the failure to do so. The term "other similar action" refers to, for example, a vaccination and blood or organ donation. An injury caused by an erroneous prescription or dosage of drugs may also be compensated for as a treatment injury.

A prerequisite for compensation is that an experienced medical professional could have performed a different procedure in the examination or treatment situation in question, thereby avoiding the injury. Consequently, a treatment injury may be, for example, a post-operative complication, such as a nerve injury or a delay in diagnosis, which could have been avoided by an experienced professional.

The content and level of proficiency required by experienced healthcare personnel varies. For example, a general practitioner at a healthcare centre and a specialist at a university hospital have different requirements.

The majority of rejected claims are due to the fact that regardless of appropriate treatment, the injury could not have been entirely avoided. It is not always possible to achieve satisfactory treatment results, for example, due to the serious nature of an illness or trauma. Such consequences are not compensated for if the procedures were in line with the standards required of an experienced medical professional, and yet the injury could not be avoided. Injuries may, however, be compensated for as an unreasonable injury in cases where the injury is caused by a severe and sudden consequence of the treatment.

Even if a sufficient level of competence is not always achieved by a medical professional, this does not necessarily mean that a patient will incur a compensable bodily injury as a result. For example, a correct diagnosis is occasionally reached only after some delay, even though proper examinations could have enabled an earlier diagnosis. The injury is not compensable if the delay has not affected the content, the prognosis or the end result of the treatment.