How to Make Decisions for Someone Who Lacks Mental Capacity in the UK
Imagine your elderly dad is no longer able to manage his finances. Or perhaps your friend has a serious illness and can’t make informed medical decisions. When someone loses the ability to make choices about their life, it can be overwhelming—and knowing what to do next is crucial. In the UK, there are clear rules and options to help guide you through this sensitive responsibility.
In this guide, we’ll walk you through how to make decisions for someone who lacks mental capacity, the legal tools available, and the steps you can take to protect your loved ones—all in simple, everyday language.
What Does “Lacking Mental Capacity” Mean?
Let’s start with the basics: What exactly does it mean when someone “lacks capacity”?
Mental capacity refers to a person’s ability to:
- Understand information relevant to a decision
- Retain that information long enough to make the decision
- Weigh up the options
- Communicate their choice
If someone can’t do one or more of these things—whether due to a condition like dementia, a brain injury, or even a temporary illness—they may be considered to lack the mental capacity to make certain decisions on their own.
Important: Capacity Can Vary
Mental capacity isn’t black and white. It can come and go. Someone might be able to decide what to wear or what to eat, but not how to manage their investments. That’s why the law says we need to assess capacity decision by decision.
Step One: Try to Help the Person Decide
Here's something many people forget: just because someone is struggling doesn’t automatically mean they can’t decide for themselves. Your first responsibility is to support them in making their own decision.
Ask yourself:
- Can I explain it in a simpler way?
- Would using pictures or examples help?
- Is this a good time of day for them?
- Are they calm and alert right now?
Sometimes all that’s needed is a bit of patience and a clearer explanation.
Step Two: Assess Their Mental Capacity
If you’ve tried everything to support them but they still can’t understand or make a decision, you’ll need to assess their capacity.
The test is based on the Mental Capacity Act 2005 and includes two parts:
- Is there an impairment or disturbance in how their brain or mind works (e.g., Alzheimer’s, stroke, or mental illness)?
- Does this mean they can't understand, retain, use or weigh information to make a decision, or communicate it?
Both parts must be true for someone to be considered legally lacking capacity.
Who Gets to Decide When Someone Can’t?
So what if the person truly can't decide—who steps in? That depends.
1. There's a Lasting Power of Attorney (LPA)
Good news—if they planned ahead and made an LPA, that person (called the attorney) can step in to make decisions on their behalf.
There are two types of LPAs:
- Health and Welfare: For decisions about medical treatment, care, or daily routine
- Property and Financial Affairs: For managing money, bills, and assets
The attorney must always act in the person’s best interests. That means putting their needs, preferences, and past wishes first—even if it’s hard or inconvenient.
2. No LPA? A Deputy Might Be Required
If there's no LPA and the person can’t decide for themselves, someone might need to apply to the Court of Protection to become a Deputy. This is often a close family member, but it can also be a professional like a solicitor.
The court will decide who’s best suited for the role, and the Deputy must regularly report how they’re managing things.
3. One-Off Decisions? The Court Can Help
If it's not practical to appoint a lasting Deputy, you can ask the Court of Protection to make a specific decision—like giving consent for a medical procedure or selling a property.
How Should You Make Decisions for Someone Else?
If you're in charge of making decisions for someone who lacks capacity, you must follow the five key principles of the Mental Capacity Act.
1. Presume Capacity
Always start by assuming the person can make their own decision—don’t assume otherwise just because of a diagnosis or age.
2. Support Decision-Making
Give them every chance to decide for themselves. Remember: Temporary confusion doesn’t mean permanent incapacity!
3. Respect Unwise Decisions
This one is tough—just because someone wants to do something risky doesn’t mean they lack capacity. We all make bad choices sometimes, right?
4. Make Decisions in Their Best Interests
Think beyond what’s easiest or cheapest. Consider what the person would want based on their values, beliefs, past decisions, and family input.
5. Choose the Least Restrictive Option
Always try to find the solution that allows the person as much freedom and independence as possible—while still keeping them safe.
Everyday Examples: What This Looks Like
Let’s look at real-life situations where this guidance comes into play.
Scenario 1: Elderly Parent with Dementia
Your mum has mid-stage dementia and keeps forgetting to pay her bills. She also can’t remember what the payments are for, even after they’re explained. You have an LPA for her finances, so you start managing her money to make sure her bills are paid and her account isn’t overdrawn. You still ask her opinion when something big comes up, like selling her car—even if the decision is ultimately yours.
Scenario 2: Brother with Learning Disabilities
Your brother has learning difficulties and wants to move into supported housing. He understands what it means and is excited about the independence. Just because others think he’s making a risky choice doesn’t mean you can override him—he has capacity and the law supports his right to choose.
Scenario 3: Friend in Hospital After a Stroke
Your friend, who hasn’t made an LPA, is in hospital unconscious after a stroke. The doctors need to decide on treatment, so they consult with next of kin—but they’re also guided by what your friend has said in the past, their known views, and medical advice. If a big decision comes up—like life support withdrawal—the court may step in.
What If There's a Disagreement?
Family members don’t always agree on what’s “best.” If there’s a serious conflict or someone seems to be acting against the person’s interests, you can get help from the Court of Protection. You can also involve the Office of the Public Guardian if an attorney or deputy isn’t doing their job.
Sometimes, mediation or a second opinion from social services can help avoid taking it to court.
Tips to Make Things Easier
Here are some practical steps you can take today, especially if you or someone you love is at risk of losing capacity in the future:
- Create a Lasting Power of Attorney early—don’t wait until it’s too late.
- Talk to your family about your wishes before you’re unable to express them.
- Write an advance statement to include in health care planning.
- Keep records of important decisions made on someone’s behalf to show you're acting in their best interests.
Final Thoughts
Making decisions for someone else isn’t easy—it comes with emotional, legal, and practical challenges. But the UK has solid rules in place to help protect vulnerable individuals and guide those stepping in to support them.
The key? Act with compassion, follow the law, and always consider what the person would want—not just what’s easiest for you.
Want to learn more, or need detailed forms and legal steps?
Visit the official guidance at: https://www.gov.uk/make-decisions-for-someone
