When is dehydration dangerous?

I've been dehydrated multiple nights in a row due to rapid weight loss this week, I have lost around 3 pounds since my barbecue on Sunday and it is now Thursday, on Tuesday, I had gained 2 pounds after the barbecue from digesting the food I ate there. As of Thursday, I am 1 pound skinnier than I was before the barbecue happened. My weight loss supplement helps me lose weight but it also leads to thirst, sometimes the thirst is so intense it affects my sleep.

When is dehydration dangerous?
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