Right to Refuse Treatment Ontario: What the Law Actually Allows

Capable Patients Can Refuse Any Treatment

Under the Health Care Consent Act, a mentally capable patient in Ontario has an absolute right to refuse any medical treatment — including life-saving treatment. A physician who provides treatment without consent, or continues treatment after a capable patient has withdrawn consent, commits a battery under Ontario law. This right applies regardless of whether the physician considers the refusal unwise, irrational, or medically harmful.

The right is unconditional. A patient can refuse a blood transfusion, decline chemotherapy, withdraw consent to a ventilator, or reject surgery for a treatable condition. The physician's obligation is to ensure the patient understands the nature of the treatment, the expected benefits, the material risks, and the consequences of refusal. If the patient understands all of this and still refuses, the refusal stands.

What Happens When You Lose Capacity

The right to refuse treatment survives incapacity — but only through the substitute decision-maker framework. When a patient is found incapable of consenting to a specific treatment, their SDM steps in and has the same right to consent to or refuse treatment on the patient's behalf.

The SDM must base their decision on the patient's last known capable wishes. If the patient previously stated — while capable and at least 16 years old — that they wanted to refuse a specific treatment under specific circumstances, the SDM is legally obligated to honour that refusal, even if the SDM personally disagrees with it.

If no prior wishes exist, the SDM falls back to the "best interests" standard: weighing the treatment's expected benefits against its risks, considering the patient's values and beliefs, and choosing the least restrictive and intrusive option.

Documenting Treatment Refusals in Your POA-PC

The most reliable way to ensure your treatment refusals are honoured after you lose capacity is to document them in a Power of Attorney for Personal Care. General statements like "I refuse all life-sustaining treatment" are routinely challenged by physicians because they do not account for the range of clinical scenarios where life-sustaining treatment might be temporary, reversible, or clearly beneficial.

Effective refusal clauses distinguish between scenarios:

• Refusing CPR in the context of a terminal illness versus allowing it for a sudden cardiac event during an otherwise treatable condition
• Refusing long-term mechanical ventilation while accepting short-term ventilation as a bridge during post-surgical recovery
• Refusing artificial nutrition and hydration during active dying while accepting it during a temporary condition where recovery is expected
• Refusing specific treatments on religious or personal grounds regardless of the clinical context

Each refusal should include the reasoning behind it. Your SDM will face situations you did not specifically anticipate, and understanding your values helps them apply your documented refusals to novel circumstances.

When Refusal Gets Complicated

Two situations create friction in practice:

The physician believes the patient is incapable: If a patient refuses treatment and the physician suspects the patient lacks the capacity to make that decision — perhaps due to delirium, medication effects, or cognitive decline — the physician can find the patient incapable for that specific treatment decision and turn to the SDM instead. The patient can challenge the capacity finding by applying to the Consent and Capacity Board, which must hold a hearing within seven days.

The SDM refuses treatment the physician considers essential: When an SDM refuses treatment on behalf of an incapable patient, the physician faces a conflict if the physician believes the refusal does not align with the patient's prior wishes or best interests. The physician's remedy is a Form G application to the Consent and Capacity Board. The CCB will determine whether the SDM's refusal is consistent with the patient's wishes or, failing that, with the patient's best interests.

The Limits of Refusal

The right to refuse treatment does not include the right to demand specific treatments. A patient can refuse chemotherapy, but they cannot demand an experimental therapy the physician considers inappropriate. This distinction matters because families sometimes frame treatment demands as refusals of the alternative — "we refuse comfort care and insist on aggressive treatment" — which does not create an obligation on the clinical team to provide the demanded intervention.

The right to refuse also does not extend to public health measures that are imposed by law, such as involuntary isolation orders for certain communicable diseases. These are separate statutory frameworks that operate outside the HCCA's consent model.

Making Your Refusals Stick

Document your treatment preferences in a Power of Attorney for Personal Care with enough specificity that your SDM can apply them to the clinical decisions they will actually face. Have the conversation with your attorney so they understand not just what you want but why. And make sure the signed document is accessible — not locked in a safety deposit box that no one can reach during a weekend hospitalization.

Our Ontario Advance Directive & Living Will Kit includes treatment preference worksheets that walk through each major intervention category, help you articulate your refusals in clinically specific language, and provide scripts for the conversation with your POA-PC attorney.

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