The following criteria that have been deemed to be necessary to reach to a decision by the patient with regard to proposed line of treatment have been defined: Assessment of these criteria for decision-making capacity is an essential part of the process of informed consent.

Understanding: Is the patient able to grasp or comprehend the meaning of the information provided to him/her by the doctor and retain that knowledge? This includes information about the disease condition, the proposed treatment or alternative treatments, the associated benefits and risk of proposed treatments, alternative treatments as well as no treatment. The ability to understand the relevant facts has a great role in the decision making ability of the patient because if the patient does not understand the information given, he/she cannot decide on information that is relevant to their situation.

The information must be simple and clear and imparted in language, which the patient can understand, avoiding too many medical terms. Memory problems, intelligence can affect understanding of the information.

Expressing a choice: Is the patient able to clearly communicate to the doctor his/her choice of preferred treatment option from the multiple proposed treatment options? Is the patient able to maintain a relatively stable decision regarding treatment choice for it to be implemented?

Patients may often change their mind about their treatment choice and withdraw consent at any time. This does not mean that the patient lacks the capacity to make a decision if the patient is able to give a justifiable rationale for the change in decision. But, too many changes in decision making may put a question mark on the capacity of the patient to come to a decision.

Appreciation: Mere understanding of the facts given to a patient does not suffice. Is the patient able to relate the information about the proposed diagnostic and treatment intervention and the likely consequences to himself/herself directly? Whether the patient understands the consequence of refusal of treatment?

Reasoning: Is the patient able to rationally use the relevant information and give reasons for selecting a particular treatment option keeping his best interests in mind? Reasoning is the process by which the patient arrives at a decision and not the final decision as chosen by the patient. If a patient lacks reasoning, he/she will not be able to compare the benefits and risk of various treatment options in a rational or logical manner. Conditions like psychosis, depression, any phobia, dementia affect reasoning.