Somebody will write a care plan about you one day. It might be years away, it might be next month, and it will almost certainly be written by a person who met you a fortnight ago.

They will do a careful job. They will get your medication right, your allergies right, your mobility right. Then they will reach the part of the form that asks what matters to you, and they will write down whatever they have managed to work out, or whatever your daughter remembered under pressure in an office on the worst afternoon of her year.

That page is the one that decides what your days feel like. And it is the only page you can write in advance.

First, three different documents that all get called a care plan

Most of the confusion about this comes from the fact that people use one phrase for three separate things. It is worth separating them, because you can only write one of them yourself, and it happens to be the useful one.

1. The clinical care plan. This is the working document a care home, hospital or home care agency writes and keeps. It covers medication, moving and handling, skin integrity, nutrition, falls risk, personal care. It is a legal record, it belongs to the provider, and they must review and update it. You cannot write this, and you should not try. You can read it, question it and ask for things to be added, which is a right worth using.

2. The personal one, sometimes called an advance statement. This is where you write down who you are, how you like things done and what you would want if you could no longer say. It is not legally binding. It is, however, the thing the clinical plan gets built from, and in England and Wales anybody making a decision in your best interests under the Mental Capacity Act has to take your known wishes and feelings into account. Written down, dated and handed over, those wishes stop being hearsay. This is the one you write.

3. The legal documents. A lasting power of attorney for health and welfare says who may decide for you. An advance decision to refuse treatment says what medical treatment you refuse, and that one is legally binding when it is valid and applies to the situation. A will deals with everything afterwards. These are separate, they have their own rules, and a profile does not replace any of them. Get proper advice, and then record in your profile that they exist and where they are kept, because a document nobody can find helps nobody.

If you have ever filled in a This is Me leaflet from the Alzheimer's Society, or a hospital passport, you have already done a short version of number two. Both are good. Both are also deliberately brief, because they were designed to be filled in quickly at a hospital admission. What follows is the longer conversation those documents open.

Why you write it now, and not later

Because of when it gets asked for.

Nobody sits down calmly in June to write a care plan. It happens after a fall, or a hospital discharge that has to be sorted out by Friday, or a diagnosis that has knocked the whole family sideways. The form arrives at the point when everybody involved is exhausted, frightened and trying to make decisions at speed.

So the honest answers are missing. Not because anybody is careless, but because "what matters to your mother" is an enormous question to answer in a corridor. What gets written is the shortest true thing anybody can think of. She likes a cup of tea. She was a teacher. She is very independent.

The other reason is harder. If the condition anybody is worried about is dementia, then the person best qualified to write this is losing the ability to do it. There is a window, and it does not stay open. A profile written by somebody about themselves, while they can still be funny and difficult and specific about it, is worth ten written about them afterwards.

This is also true if you are perfectly well and forty-five. You are not writing it because you expect to need it. You are writing it so that it exists.

What actually goes in it

Not a life story. Not a medical history. The things that change what a shift feels like, and that nobody can guess.

How you are addressed

What you are called, and what you must never be called. Love, sweetheart, darling, pet. For some people that is warmth. For others it is the moment they stop being a person with a job and a history and become somebody being managed. Nobody can tell which you are by looking.

Who you are, and were

What you did for a living, and what it meant to you. What you could talk about for hours. Be specific. Not "gardening" but dahlias, and the show at Shrewsbury, and the year you finally beat your brother-in-law. Specific gives a stranger somewhere to start a conversation. General gives them nothing.

How your mind works

You do not need a diagnosis to describe this, and most people who write it have no label at all. Whether you need everything in sight or cannot bear clutter. Whether you have to know why before you will do a thing. How long you need to answer a question. Whether you have always found a room full of people exhausting.

That last one matters more than it looks. If you have never liked crowds, and you decline the singalong, that is you being yourself. Written down in advance, it stays that. Not written down, it can be read as becoming withdrawn, and withdrawn is a word that leads somewhere.

Your senses

Noise, light, temperature, texture, smell. What the covers should weigh. Whether the television being on in the corner is company or torture. These are the small physical things that decide whether a day is bearable, and they are the easiest to get right once somebody knows.

Your day, in order

What you do first in the morning and in what sequence. When you eat. When you want to be left alone. What you do last thing before bed. A care home has to run to a shared clock, and it can accommodate a great deal of somebody's own clock inside that, but only if it knows what it is.

How to tell when something is wrong

This is the page that prevents most trouble, and almost nobody writes it.

What do you look like ten minutes before anybody else would notice? Do you go quiet, go looking for something, get suddenly polite, start tidying? What makes it worse: being hurried, being corrected, being touched without warning, being told you are wrong? What actually helps: a particular person, a hot drink, going outside, being left alone for twenty minutes?

Then put a number on the recovery. "I need twenty minutes" is an instruction. "Give her some space" is a shrug.

What you want if you ever need care

Where. Who you would want near you. What you want in the room. What you want offered and what you never want served. How you want to be helped with personal care, and by whom. What would matter at the very end.

People leave this section for later. It is the section a care team most wants and has no way of finding out on its own.

Write it so it survives a shift change

This is the difference between a document that changes something and a document in a drawer.

A care home runs on handovers. Days, nights, the bank staff, the agency carer who has never met you. A line only works if a stranger can act on it at three in the morning without asking anybody.

So write instructions, not adjectives, and attach the reason. The reason is what makes a busy person keep doing it.

Instead of "likes her things around her":

I use visible objects to remember. Please do not tidy items from the windowsill or the top of the chest of drawers. This is how I keep track of things, not clutter. They may be dusted around and must go back exactly where they were.

Instead of "can get agitated in the evening":

If I am unsettled after about four o'clock, check whether I am too warm before anything else. Ask if I want to go outside. Do not ask me several questions at once. I need about twenty minutes on my own and then I am fine.

Instead of "likes music":

Play Moon River if I am distressed and looking for my husband. It was our song. It may make me cry, and that is all right, it settles me afterwards.

The second version of each survives the night shift. The first does not.

Where to put it once it is written

Give it away. A profile in your own filing cabinet has done nothing.

  • Give a copy to whoever would be called first. Not a mention of it, an actual copy.
  • If you are moving into a care home, hand it over before the move, with the admission paperwork. Ask for it to go in the care plan rather than the personal file.
  • Ask for one page to be copied onto the front of the plan, where staff look. If they will only take one, make it how to tell when something is wrong.
  • Take it to hospital. Ward staff have no history for you at all, and this is the only thing that will tell them.
  • Keep a copy in the room. It works as a conversation prompt as much as a record, and it is the most useful thing you can hand a new member of staff.
  • Date it, and look at it again in a year. People change.

Write yours, free

The Personhood Profile is the template I built for this. Fifteen sections, forty-nine questions, in your own words and in the first person, so that whatever ends up in front of a care team sounds like you rather than about you.

It is free, there is no account, and nothing you type ever leaves your device. It runs in your browser, saves on your own computer, and I could not read it if I wanted to. When you have finished, you print it or save the file, and what happens to it after that is entirely yours.

If you would rather write in pen, the same questions are in a paperback called Before You Read My Notes, in large print with room to answer properly. Some people fill it in on a screen. Some people want a book they can sit down with, or take into a relative's room and work through together. Both end up in the same place.

There is also a version for care homes, which builds the same profile about a resident with the family, and prints a one page care card for the front of the plan.

Somebody is going to write a plan about you. You do not get to write it. You do get to decide how much of it is guesswork.