Two coffees and a headache at three

Seven o'clock, a coffee. The first one is the good one. Ten o'clock, at your desk, another, because someone's going to the machine and it would be odd not to. Lunch, a sandwich, and if there's a drink it's a can of something or nothing, because you're eating at the desk and getting up is a thing. Two o'clock, a biscuit from the tin because there's a tin. Three o'clock, a headache, dull, at the front, and a heaviness that makes the screen harder to read than it was at eleven. You go for a third coffee, and it helps for twenty minutes, and then it doesn't. Four o'clock, another biscuit. Half five, you're home, and the first thing you drink that isn't coffee is a glass of wine or a cup of tea. When you go to the loo before bed, what's in the bowl is dark yellow.

That's a day of about a litre of fluid, most of it coffee, and one of those days is nothing. The trouble is that it's every day. The headache at three has been there so often that it's become "my afternoon headache", a fact about you rather than a thing with a cause. The flatness after lunch is "the post-lunch dip", which everyone gets, so it can't be helped. The biscuits are a separate problem you'll deal with separately. The coffee is a separate problem again.

These are invented, but I'd guess yours is close, give or take the biscuit. Some words. The dry day is a day like that one, where what you drink is mostly coffee and mostly before eleven. The quiet signal is thirst, which turns out to be steadier and quieter than hunger, and easier to ignore. The flat hour is the stretch after lunch when the headache and the heaviness arrive. The stand-in is whatever you reach for at the flat hour instead of a drink, the third coffee, the biscuit, the crisps. The pair is a glass of water alongside every hot drink and every meal, which chapter 16 is about. The glass first is what happens at the flat hour, a glass before the coffee or the biscuit, which chapter 17 is about. And the pale check is looking at the colour of your pee once a day, which the NHS uses and chapter 18 explains.

Before you go on, do one thing. Write down everything you drank yesterday, with rough amounts, and the time of each. Coffee, tea, cans, the glass with dinner, the wine, all of it. Then next to the list, write what colour your pee was the last time you looked. Don't change anything yet. Most people who do this find that the list is shorter than they thought and stops earlier in the day than they thought, and that the second question is harder to answer than it should be.