If reasonable medical treatment is likely to alter the degree of impairment, the impairment should not be treated as stable at this time, with the effect that a final assessment cannot be made under S24.

For medical treatment to be considered 'reasonable' in this context, it must be reasonable in all the circumstances of the case and must not expose the member to any real risk of further significant injury. If, for example, a client was unwilling to undertake major surgery based on the inherent risks associate with the surgery, it would not be reasonable to defer making a determination under S24 on this basis alone. Another example can be found in the decision of the Tribunal in Re Sims and Comcare (1998) where it was considered reasonable for the employee to refuse to take anti-depressant medication because of the advice the employee had received regarding the treatment's low chance of success and the significant side effects of the medication itself. Where it is unreasonable to require further medical treatment, the assessment under S24 should be based on the full degree of compensable impairment suffered by the client.

In considering whether reasonableness should be judged by objective standards or by the subjective perceptions of the client, it is appropriate to adopt the approach taken by the High Court in Fazlic v Milingimbi Community Inc (1982). In that case, the Court had regard to what the employee knew about the proposed treatment and whether his or her concerns were reasonable, given that state of knowledge: They also stated it was necessary to take into account “all the circumstances known to...and affecting [the worker]” in addition to the medical advice they had received.

The Federal Court added in Filla v Comcare (2001) that “even if the worker has received medical advice to submit to an operation and even if that advice means that the worker knows of cogent factors favouring his submitting to that operation, still, other circumstances known to and affecting the worker may mean that the worker's refusal to submit to the operation is neither the result of baseless fear nor properly to be characterised as unreasonable”. They went on to include a worker's religious beliefs as something that could “repel any suggestion of unreasonableness in refusing to submit to that surgery”.