SDM Hierarchy Ontario: Who Makes Medical Decisions When You Can't
The Province Picks Your Medical Decision-Maker — Unless You Do It First
If you become mentally incapable of consenting to medical treatment in Ontario and you have not signed a Power of Attorney for Personal Care, the Health Care Consent Act assigns someone to make decisions for you. You do not get to choose who. The Act uses a fixed nine-tier hierarchy, and the first available person who meets the requirements steps into the role automatically.
For many families, the person the law selects is not the person the patient would have chosen. And the consequences of that mismatch only surface during a crisis, when it is too late to change anything.
The Nine-Tier SDM Hierarchy Under the HCCA
Section 20 of the Health Care Consent Act sets out the priority order. When a healthcare provider determines that a patient lacks the capacity to consent to a specific treatment, they must turn to the highest-ranking available person on this list:
- Court-appointed guardian of the person — a judge has formally appointed this person to make personal care decisions
- Attorney named in a Power of Attorney for Personal Care — the person you chose and legally documented
- Representative appointed by the Consent and Capacity Board — the CCB has designated someone through a formal hearing
- Spouse or common-law partner — including same-sex partners who have cohabited for at least one year
- Child (age 16 or older) or parent — equally ranked, which is where sibling deadlocks happen
- Parent with only a right of access — non-custodial parents in family law contexts
- Sibling — also equally ranked among multiple siblings
- Any other relative — by blood, marriage, or adoption
- Office of the Public Guardian and Trustee (OPGT) — the absolute last resort when no one else is available or willing
The hierarchy is rigid. A sibling cannot override a spouse. An adult child cannot override a court-appointed guardian. And when the law reaches the OPGT at tier 9, the family loses all control over the decision.
Why Equal Ranking Creates Family Deadlocks
The hierarchy's most dangerous feature is that some tiers contain multiple people who share equal authority. If a patient has three adult children and no spouse, all three children are equally ranked SDMs at tier 5. They must make decisions unanimously.
If the siblings disagree about whether to consent to surgery, authorize palliative sedation, or approve a transfer to long-term care, the healthcare provider cannot break the tie. The physician cannot pick one child's opinion over another's. Instead, the clinical team must attempt mediation — often involving hospital ethicists and social workers — and if that fails, the decision gets referred to the OPGT.
The OPGT then makes the decision on behalf of the family. The public trustee charges regulated fees: 3% on receipts and disbursements plus 0.6% annually on managed assets. More importantly, the family has now lost the ability to direct their parent's care.
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How Capacity Works in Ontario
Capacity in Ontario is decision-specific and moment-specific. A person might be capable of deciding what to eat for dinner but incapable of consenting to a complex surgical procedure. The healthcare professional proposing the specific treatment is the one who assesses whether the patient can understand the relevant information and appreciate the reasonably foreseeable consequences.
This means a patient could have multiple different SDMs for different decisions throughout the same hospital stay — whoever is available and highest-ranking at the moment the specific treatment is proposed.
How to Override the Default Hierarchy
The only reliable way to override the statutory hierarchy is to sign a Power of Attorney for Personal Care while you are still mentally capable. This document places your chosen attorney at tier 2 of the hierarchy — above your spouse, your children, and your siblings. Only a court-appointed guardian (tier 1) ranks higher, and courts rarely appoint guardians when a valid POA-PC exists.
Your POA-PC can also include specific instructions about your treatment preferences, which your attorney is legally obligated to follow. Without these instructions, any SDM — whether your chosen attorney or the default person from the hierarchy — must make decisions based on your "last known capable wishes." If you never communicated any wishes, they fall back to "best interests," which is a subjective standard that frequently leads to family conflict.
What the SDM Must Actually Do
An SDM is not free to make whatever decision they personally prefer. Under section 21 of the HCCA, the SDM must make the decision the incapable person would have made based on their last known capable wishes — wishes they expressed while they were age 16 or older and had the mental capacity to form them.
If no wishes are known, the SDM must act in the patient's best interests, considering the patient's values, whether the treatment is likely to improve their condition, and the expected benefits versus risks.
Healthcare providers can challenge an SDM who appears to be acting outside these guidelines by filing a Form G application with the Consent and Capacity Board. The CCB can then order the SDM to comply or replace them entirely.
What to Do Now
If you have not signed a Power of Attorney for Personal Care, the statutory hierarchy is already assigned to your family. Whether that default matches your actual wishes is something only you can answer — and only while you still have the capacity to change it.
Our Ontario Advance Directive & Living Will Kit includes the complete framework for appointing your POA-PC attorney, documenting your treatment preferences so the SDM hierarchy never comes into play, and a sibling-deadlock prevention worksheet for families with multiple equally ranked decision-makers.
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