When a patient can make their own decisions, no one else has that authority. But when someone becomes incapacitated, the right to make medical choices transfers to a specific person or set of people, determined by a combination of advance planning and state law. The answer depends on whether the patient named someone ahead of time, whether family members are available, and what type of decision needs to be made.
The Patient Comes First
A competent adult always has the right to accept or refuse medical treatment. Before anyone else can step in, a physician must determine that the patient lacks what’s called “decision-making capacity.” This isn’t a single yes-or-no test. Clinicians evaluate four specific abilities: whether the patient can understand the information being shared about their condition and treatment options, whether they can apply that information to their own situation, whether their choices reflect a logical reasoning process, and whether they can clearly communicate a decision.
All four must be present for a patient to retain decision-making authority. A patient who understands their diagnosis but cannot weigh the consequences of treatment options, for example, may lack capacity for that particular decision. Capacity can also fluctuate. Someone who is confused after surgery might regain full decision-making ability once the anesthesia clears. Losing capacity for one decision doesn’t automatically mean losing it for all decisions.
A Healthcare Power of Attorney
The strongest tool for controlling who makes your medical decisions is a healthcare power of attorney, sometimes called a durable power of attorney for healthcare or a healthcare proxy. This legal document lets you name a specific person, your “agent,” to make medical decisions if you become unable to make them yourself. The agent’s authority kicks in only when you lose capacity and typically ends when you regain it.
Requirements for a valid healthcare power of attorney vary by state, but most require a witness signature. In Illinois, for instance, the witness must be at least 18, cannot be the named agent, cannot be related to the patient by blood, marriage, or adoption, and cannot be the patient’s physician or an owner of the facility where the patient receives care. Some states require notarization; others, like Illinois, do not.
You can revoke a healthcare power of attorney at any time, even if you currently lack capacity to make medical decisions on your own. You can cancel it by telling your agent directly (verbally or in writing), informing your doctor or care facility, signing a new document naming a different agent, or simply taking any action that clearly shows your intent to revoke it. If your spouse is your agent and you divorce, the document is automatically revoked in many states.
How a Living Will Differs
A living will is a separate document that doesn’t name a decision-maker. Instead, it records your specific wishes about end-of-life treatment: whether you want to be resuscitated, placed on life support, given tube feeding, or kept on a mechanical ventilator. It can also state preferences for comfort care, palliative care, pain management, and organ donation. A living will only takes effect when you are both incapacitated and there is no realistic medical hope of recovery.
The two documents work best together. A living will covers the specific scenarios you can anticipate, while a healthcare power of attorney gives a trusted person flexibility to handle situations you didn’t predict. You can also give your agent authority to carry out or interpret your living will instructions if any ambiguity arises.
When No One Is Named in Advance
Most people never complete advance directives. For the majority who don’t, state law determines who steps in. Thirty-five states have what’s known as a “surrogacy ladder,” a ranked list of people authorized to make medical decisions for an incapacitated patient. The highest-priority person on the list who is available and willing to serve becomes the surrogate.
The top of the ladder is remarkably consistent across states. Nearly all place the spouse first, followed by adult children, then parents. Eight states also insert a domestic partner or “chosen adult” at or near the top of the list. After the top three or four rungs, states diverge significantly. Some include adult siblings, grandchildren, or close friends. Others stop the list short, leaving fewer options if immediate family isn’t available.
When a surrogate steps in without written instructions from the patient, they’re expected to follow one of two standards. The first is substituted judgment: making the decision the patient would have made based on their known values, past statements, religious beliefs, or lifestyle choices. A surrogate who knows the patient once said they would never want to be on a ventilator long-term, for example, would use that knowledge to guide the decision. The second standard, used as a last resort when nothing is known about the patient’s wishes, is the best interest standard. Here the surrogate (and the medical team) considers what a reasonable person in the patient’s situation would want, based on community norms and the expected benefits versus burdens of treatment.
Court-Appointed Guardians
When no surrogate is available through advance planning or the state hierarchy, or when family members disagree about treatment, a court can appoint a legal guardian. This process requires a formal petition filed in the probate court of the county where the patient lives. A medical professional must provide an expert evaluation stating that the patient is incapable of making their own decisions due to mental impairment, intellectual disability, physical illness, or chronic substance abuse.
After the application is filed, a court investigator visits the patient independently and assesses both the need for guardianship and whether the proposed guardian is suitable. The investigator submits a report, and the court holds a hearing where the applicant must prove that the patient is incapacitated and that the proposed guardian is a good fit. A guardian of the person receives broad authority over healthcare decisions, residential placement, and day-to-day care.
Courts are cautious about conflicts of interest. In Ohio, for example, a paid care provider generally cannot also serve as a patient’s guardian unless they are a family member and the court specifically approves the arrangement. Non-family members are strictly prohibited from serving as both guardian and paid provider for the same person.
Emergency Situations
In a medical emergency, physicians can treat a patient without consent from a surrogate or agent. The legal basis is implied consent: the law assumes that a reasonable person facing a life-threatening situation would agree to treatment. This applies when the patient is unconscious or otherwise unable to communicate, no surrogate is immediately reachable, and delaying treatment would risk death or serious harm.
The definition of “emergency” matters. Courts have defined it as narrowly as an immediate threat of loss of life or limb and as broadly as a situation of acute suffering with a condition that is objectively demonstrable. In psychiatric emergencies, courts have expanded the definition to include not just the risk of imminent violence or self-harm but also the potential for immediate, substantial, and irreversible deterioration of a serious mental illness where even the smallest delay would be intolerable. Once the emergency passes, however, the standard rules apply, and a surrogate or agent must be involved in ongoing treatment decisions.
Decisions for Minors
For children under 18, parents or legal guardians hold decision-making authority by default. But there are important exceptions. Every state has laws allowing minors to consent to treatment on their own for specific conditions, typically emergency care, sexually transmitted infections, substance abuse treatment, mental health care, pregnancy-related care, and contraception.
Beyond those statutory carve-outs, the “mature minor doctrine” recognizes that some adolescents are capable of making informed medical decisions. Courts and clinicians generally consider minors older than 14 capable of consenting to low-risk treatments when they demonstrate an adult-like understanding of the decision and its consequences. Emancipated minors, those who are legally independent from their parents through marriage, military service, or court order, have full authority over their own healthcare regardless of age.
How State Laws Vary
There is no single federal law governing medical decision-making for incapacitated adults. The Uniform Health-Care Decisions Act was designed to standardize the rules, but only a handful of states have adopted it, including California, Delaware, Hawaii, Maine, Mississippi, and New Mexico. The remaining states each have their own combination of advance directive statutes, surrogate consent laws, and guardianship rules. This means the specific hierarchy of surrogates, the requirements for a valid healthcare power of attorney, and the process for appointing a guardian can look quite different depending on where the patient lives.
If you’re planning ahead, the most reliable step is completing both a healthcare power of attorney and a living will under the laws of your state. These documents override the default surrogate hierarchy and ensure the person you trust most is the one making choices on your behalf.