I have a slight suspicion that every time I consume something with caffeine it has a specific effect on me.
A good cup of black or green tea: Slight headaches at some times.
A cup of coffee (from work coffee machine): Depending on strenght slight attention issues or headaches.
A cup of coffee from a coffee shop which roasts its own coffee: One time a bit of stronger attention issues than the work coffee.
I usually notice it right away after consuming.
But I also have a very strong issue with staying hydrated.
Usually drink 0.5-1l per day until I notice the usual dehydrated-headache or when I am really focused and loosing it at times.
Usually it’s less prevelant at evening/night times.
No, if you’re a regularly consume caffeine, it has very minimal to no dehydration effects except in extreme cases, such as consuming significantly more caffeine in a day than you usually do. IIt was like 10+ years ago that I really dug into this, so my memory may be a bit fuzzy, but the general idea is that caffeine basically irritates the bladder causing you to pee more frequently, but the total volume of water loss is the same.
Searching for “caffeine dehydration” brings up tons of other articles saying that the dehydration thing is a myth. Here’s a scientific study comparing effects of caffeine on hydration:
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3886980/