Occasionally I have to get up very early for flights, surveys etc and only get a couple of hours sleep. As soon as I wake up, my throat feels completely dry and I am extremely dehydrated. The only way to put it right is to drink silly amounts of water.

But if I was to get a full 7/8 or so hours sleep rest (i.e. longer without water), I do not feel this and am not thirsty at all.

Any ideas why this happens?

1 Answer 1


The feeling of dehydration may be due to dry mouth, for example, due to stress related to getting up early. Feeling unrefreshed due to lack of sleep may also make you feel dehydrated. But this is not dehydration.

When you are actually dehydrated, you lose body weight. It is considered that you are mildly dehydrated when you lose at least 1% of body weight, so at least 0.7 kg (1.5 lbs) in a 70 kg (154 lbs) person (Defense Technical Information Center).

So, to check if you are really dehydrated, weigh yourself and compare your weight with what is your usual weight (checked in some "normal" morning when you think you are well hydrated, in same clothes, after emptying your bladder and bowel and before eating anything).

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