Professional Role · Topic 6 of 21

Informed Consent & Decision-Making Capacity

Professional role · consent and capacity

Informed Consent & Decision-Making Capacity

Valid consent needs a capable patient, full disclosure and a free choice; capacity is decision-specific and judged by the treating clinician, not a court.

Key numbers

Capacity = understand, appreciate, reason, communicate4 abilities

01 · Defined byCapacity = understand, appreciate, reason, communicate

A patient has decision-making capacity when able to understand the information, appreciate how it applies to the patient's own situation, reason about the options in line with personal values, and communicate a clear choice.

02 · Defined byDisclose condition, options, risks, benefits, alternatives

Informed consent needs a capable patient choosing freely after disclosure of the condition and its untreated course, the proposed intervention, risks, benefits and burdens of each option including none, the clinician's recommendation, and uncertainties.

03 · The ruleEmergency exception: treat under presumed consent

When treatment is urgent, the patient cannot decide and no surrogate is available, treat under presumed consent unless there is evidence of refusal (POLST, DNR); inform the patient or surrogate at the earliest opportunity.

The rules

Know these

A capable patient may refuse any treatment must knowA patient with capacity may refuse any treatment, including life-sustaining care, even if death results; refusal is not suicide and is not by itself evidence of incapacity — a puzzling refusal calls for more discussion.

Higher-risk decisions need more capacityCapacity is decision-specific and the bar rises with the complexity and risk of the decision: a patient with dementia may consent to an IV line or name a surrogate yet lack capacity for high-risk surgery.

Treating clinician determines capacity; psychiatry optionalAny treating clinician authorized by state law can determine capacity and should document how; psychiatric consultation is optional but prudent with schizophrenia or delusional disorders, and the final determination stays with the treating team.

Capacity does not require the 'right' choiceA patient need not make the choice the clinician would make — only show a reasoned use of the information; a capable Jehovah's Witness refusing blood products is honored.

Bridge language barriers before obtaining consentFederal law requires reasonable steps to communicate with patients who do not speak English or have other communication barriers — arrange interpretation; whoever obtains consent must be able to explain the intervention and answer questions.

Presentation

What you'll see

When to formally assess capacityFormally evaluate capacity after an acute change in mental status, refusal of a clearly beneficial treatment, quick agreement to a risky procedure without weighing it, or risk factors such as dementia or chronic psychiatric illness.

Management

Orders

Treat reversible causes, then reassess capacityCapacity fluctuates: delirium, intoxication, hypoxia, metabolic derangement, medication effects and acute psychiatric illness can remove it temporarily — treat the cause and reassess before turning to a surrogate when the decision can wait.

Assess capacity in a structured sequenceAssess capacity stepwise: remove communication barriers (hearing, language, jargon), look for reversible causes, consider the patient's values and culture, then use a directed interview on the four abilities, adding a formal tool if still unclear.

Document the consent conversation, not just signatureDocument the informed consent discussion and the patient's or surrogate's decision in the record; a signed form, when obtained, is added to the record but does not replace the conversation.

No capacity: turn to the authorized surrogateIf capacity cannot be restored, a surrogate consents: a court-appointed guardian, the agent named in a durable power of attorney for health care, or the state-law default surrogate; still involve the patient.

Capacity or competence?

Commonly confused

Who determines it	The treating clinician
Scope	One specific decision
Over time	Fluctuates — treat reversible causes and reassess
When it is lacking	Agent or default surrogate decides

Commonly confused

Tell apart

Cognitive scores do not establish capacityFormal tools such as the Aid to Capacity Evaluation (ACE) improve accuracy; a cognitive screen such as the MMSE helps only at its extremes and cannot by itself establish or exclude capacity.

Implied consent only for routine low-risk careConsent may be implied for routine, low-risk care such as phlebotomy or a peripheral IV (the patient holds out an arm); invasive or risky interventions always need express informed consent.

More detail

Reference

Show 6 reference facts

Withholding pertinent information because disclosure seems medically harmful ("therapeutic privilege") is ethically unacceptable except in emergencies when the patient cannot make an informed decision; patients may, however, choose to delegate information and decisions.

Clinicians under-recognize incapacity, identifying only about 42% of patients found incapable on formal evaluation; incapacity affects about 26% of medical inpatients versus about 3% of healthy older adults.

Minors under 18 generally need a parent's or guardian's consent, but emancipated minors consent for themselves, and most states let minors consent to care such as STI treatment, contraception, substance use and mental health treatment.

When a patient judged clinically incapable still voices a preference, the clinician often cannot override it without a court finding of legal incapacity; supported decision-making agreements are a less restrictive alternative to guardianship.

If a refusal would harm others, such as a dependent minor child, seek ethics and legal consultation.

Patient decision aids (graphics, videos, interactive programs) improve patients' knowledge of options, harms and benefits and reduce decisional conflict.

Pearl

Capacity is judged one decision at a time — and disagreeing with the clinician is not incapacity.

Sources · Merck Manual Professional — Informed Consent (Pope, Aug 2025; updated Sept 2025) · Merck Manual Professional — Capacity (Competence) and Incapacity (updated Jan 2026) · Merck Manual Professional — Consent and Surrogate Decision Making (Aug 2025) · Barstow C, Shahan B, Roberts M. Evaluating Medical Decision-Making Capacity in Practice. Am Fam Physician 2018;98(1):40–46 · AMA Code of Medical Ethics Opinion 2.1.1 — Informed Consent · Appelbaum PS. Assessment of patients' competence to consent to treatment. N Engl J Med 2007;357:1834–1840 (cited by Merck; four abilities confirmed in AFP 2018) · AMA Code of Medical Ethics Opinion 2.1.3 — Withholding Information from Patients · Starter sheet built from the verified AGACNP fact map (facts reviewed 2026-10-15).