By Winnie Suen, MD, board-certified geriatrician · Last reviewed November 2026
The short answer: A doctor may decline to write a capacity letter because they don't have enough time, information, or specific training to give a reliable opinion about one particular decision. Many doctors also worry about being drawn into a family disagreement or a legal dispute. If that happens, you can ask what's missing, gather the right information, or ask for a specialist capacity evaluation.
Why this happens more often than families expect
You've been told your mom needs a "capacity letter" before she can update her will or sign a power of attorney. You ask her doctor, and the answer is no. That can feel frustrating, but it usually isn't a judgment about your family. Common reasons include:
A short visit isn't enough. Capacity is about a specific decision. Doing this well means reviewing records, talking with the person in depth, and often hearing from family. That rarely fits in a 15-minute appointment.
The doctor doesn't know the decision. A letter that says "she has capacity" without knowing whether the question is a will, a trust, or a financial POA isn't very useful, and a careful doctor knows that.
It feels outside their role. Some primary care doctors and specialists don't do these evaluations routinely and prefer to refer them out.
Concerns about conflict. If family members disagree, a doctor may be cautious about putting an opinion in writing that could be challenged later.
The doctor honestly isn't sure. Sometimes a person seems fine in a short visit but struggles at home. A responsible doctor won't sign something they can't stand behind.
What you can do next
Ask what would help. Sometimes the doctor just needs the actual question in writing ("Can Mrs. K understand and make the decision to update her will?") or a letter from the attorney.
Bring the right information. A current medication list, recent records, and specific examples of what you've noticed (with dates) all help.
Talk with the attorney. They can explain what the specific legal decision requires.
Ask for a specialist capacity evaluation. A geriatrician who does these evaluations can take the time to review records, meet with your loved one, focus on the specific decision, and write a clear opinion.
What a good capacity evaluation looks at
A clinician looks at whether the person can:
Understand the information about the decision
Appreciate how it applies to them
Reason through the options
Communicate a consistent choice
Memory problems alone don't automatically mean someone lacks capacity. Someone with mild memory loss may still be able to update a will. And making a choice others disagree with doesn't mean a person lacks capacity either.
How Discover Health can help
Dr. Winnie Suen provides capacity evaluations for medical and financial powers of attorney, will updates, and trusts for patients in Hawaii. She usually meets with your loved one at home, takes the time the evaluation needs, and gives families and attorneys a clear written opinion. Learn about Capacity Consultation or call (202) 670-8838.
This article is general information, not medical or legal advice for a specific situation.