You are cranky and/or confused
If you find yourself cranky and/or confused, then you may be dehydrated.
Sit down, grab a big drink of water (aim for a litre) and see if the symptoms go away. If you are also feeling light-headed or dizzy, then it’s even more likely that your problem is lack of fluids. Get drinking. This is serious.
So how much should you drink per day?
The old ‘eight glasses per day’ thing may have once been a good guide, but nowadays, with people exercising more and doing all sorts of extreme sports, plus warm temperatures and less healthy diets, a better aim would be around twelve drinks per day.
This number could include a couple of cups of tea or coffee, and one alcoholic beverage – a beer, or a glass of wine. So aim for eight big glasses of water, and then your other normal drinks on top of that, and you should be in good territory.