Apple. Table. Flag.

I've been here before - sitting in a psychogeriatrician's consulting room with a parent. The last time was with my mother while my father rode shotgun. This time it's my father who is in the hot seat while I have taken on his role as protector/interpreter.

I remember so clearly that day with my mother. 'Do you know what this is?' the doctor asked her, showing her his watch. She shook her head. 'And this?' he held up a pen. 'Do you know what this is for?' She didn't. He should have asked her if she knew who I was. That was a question she could have answered. That day at least. She comforted me there in the consulting room when I cried at her plight.

Sitting beside my father in the specialist's rooms I don't cry. I save my tears until later. Right now I am in competent mode, paying attention to my father's feelings and to what we need from this doctor.

The doctor asks us what we have come for, how he can help us. My father doesn't answer; he has no idea. He's here because he trusts me and I have brought him. I tell the doctor that my father has memory problems and that he barely sleeps at night, getting up, wandering around, confused and disoriented.

My father stares at me, his forehead furrowed in disbelief. 'I sleep very well,' he says. 'And I have a very good memory. I never forget anything.' My father is always loving and kind to me so he's not going to be rude but he's clearly puzzled and even shocked at my words.

'You don't mind if I test your memory?' the doctor asks.

'Not at all.' Actually there is some more conversation here and my father speaks slowly but articulately. Maybe he's not as bad as I feared. Maybe he's right and I'm wrong.

The doctor opens a printed test booklet. 'What's the date today?' he asks.

Dad concentrates but can't come up with an answer. This is not too bad. He's retired and spends most days at home. There's no reason for him to keep track of the exact date.

'That's fine. How about the month?'

Again Dad wracks his brain but can't find the answer. This is worse. It's easy to lose track of a day, but a whole month is a different dimension of forgetfulness.

'Now,' the doctor says, 'I'm going to say three words and ask you to remember them. Is that OK?'

My father nods. He's confident he'll be able to do this.

'Apple. Table. Flag.'

These are easy words. He'll remember them with no difficulty, especially because his oldest granddaughter grows apples on her organic farm. I say the words to myself, committing them to my own memory.

'Could you spell the word world backwards for me?' the doctor asks.

This is hard but Dad can't even manage one letter. He doesn't even try.

Now we're back to those words. Apple. Table. Flag. Does he remember them?

My father shakes his head. He doesn't say that one was a type of fruit and one was a piece of furniture, that they're on the tip of his tongue. He has no idea at all.

There are other tests but he fails them all. After a while the doctor says to me that he won't continue with the test; there's no point. It would only be upsetting.

We don't discuss the diagnosis. It's clear my father is suffering from dementia.

The doctor writes a prescription for a low dose of an anti psychotic to mitigate the sundowner effect that is common amongst dementia sufferers and that has my father confused and agitated in the late afternoon, and to help him sleep at night. At this point my father has fallen asleep in his chair.

We make another appointment. The doctor wants to give Dad some blood tests and see how he's going on the medication. Dad offers his hand, thanks the doctor who has been gentle and kind, and we leave.

At home I google the medication. Its side effects can include weight gain, dry mouth, drowsiness and even stroke or sudden death.

This is not what I want for my father but at the moment he dozes on and off all day and virtually doesn't sleep at all during the night. He gets agitated and aggressive with his carers and even with my older brother whom he adores. His behaviour is hard on him and even harder on his carers.

But I still feel I have failed him, that I should be able to find a way to manage him without resorting to these drugs.

And worse, I feel that I have caused the dementia. I took him to this doctor. It's because of me that he had these tests, which have led to a diagnosis, exposed his weakness to the world. If I hadn't taken him it wouldn't be true. He wouldn't have dementia. He'd just be old.

I know that what I have done is the responsible thing, that in fact I should have done it earlier. But in my heart I feel guilty of taking a lamb to the slaughter.

It's too early to tell how well the medication will work for my father. But the best I can expect is that he is calmer and sleeps better at night. That he's more 'manageable'. I feel cruel and even evil, though I don't know what else I can do.

There'll be more assessments and blood tests and I'm looking into respite care for a short period while two of his main carers are away, though he may not agree to go.

I just wish I could do better. I just wish I knew how to do this better. That's all.