I used to think I drank plenty of water, until a routine checkup ended with the doctor asking how much I actually had per day and me realizing the honest answer was “coffee, mostly.”

The tricky thing about dehydration is that by the time you feel thirsty, you are already behind. The earlier warning signs are easy to miss, but they are there if you know what to look for.

The signs that show up before thirst

Thirst is a lagging indicator. Your body flags the problem in other ways first.

• Urine color: pale yellow is good, dark amber means drink up
• Headaches: a dull headache in the afternoon is often just low fluid
• Dry skin: skin that stays tented when you pinch it is a classic sign
• Dizziness: lightheaded when you stand up can be fluid, not just blood pressure

The urine color test is the one I use every day now. It is gross but honest, and it tells you more than any app.

What I changed

I stopped trying to hit some heroic gallon-a-day target and just made water the default. A glass before every meal, a bottle on my desk, and a rule that I refill it whenever it is empty. Nothing fancy.

One thing that helped more than I expected: drinking before I am thirsty, especially in hot weather or after exercise. By the time the thirst signal fires, you have already lost a chunk of what you need.

And yes, coffee counts a little, but it is a mild diuretic, so it is not a one-for-one swap for water. Treat water as the main event.