Fill a bottle in the morning and set a timer. That is the trick. It sounds too simple to work, and I ignored it for years, but my 3pm headaches stopped within a week of starting.

The problem was invisible

I was not thirsty. That is the thing about dehydration headaches, they show up before you feel thirsty, usually in the afternoon after a morning of coffee and screens. I blamed stress, screens, sleep, everything except water. My doctor asked how much I drank and I said, “Enough,” which was a lie. I drank maybe two glasses a day.

The system that worked

I bought a 32 ounce bottle and made three rules:

1. Fill it first thing in the morning, before coffee.
2. Finish one bottle by noon and the second by 5pm.
3. Drink a full glass whenever I take my afternoon break, not a sip, a glass.

The bottle size matters. A giant bottle in front of you is a visual reminder, and the two-bottles-a-day target is easy to track. Sips from a small glass vanish into the day and you have no idea how much you drank.

What changed

Week one, I still had a headache, but it was lighter. Week two, no afternoon headache for the first time in months. Week three, my afternoon slump got noticeably shorter. I did not change anything else, same sleep, same coffee, same desk. Just water. I was honestly annoyed at how well it worked, because it meant I had been doing something stupid for years.

If you hate plain water

Add a slice of lemon, a few frozen berries, or a splash of juice. Cold water with something in it goes down much easier. Herbal tea counts too. Just skip the soda, which is mostly sugar and caffeine and makes dehydration worse in the long run.

I still get the occasional headache, but the regular 3pm one is gone. The bottle lives on my desk now, and I refill it out of habit.