I use to love coffee. I mean, I still do; but I can't tolerate it anymore. Every since I went through menopause coffee makes me jittery and irritable, which sucks. I can drink about 1/4 cup without too much side effects. Any more than that, they'd have to take me to the ER for caffiene overdose.
This did happen to a nurse that I worked with. She had stopped and got some of those energy pills. There were about four pills in the pack. She took the whole pack, not knowing that she was only supposed to take one. She became extremely irritable, she turned bright red, and had tachycardia. They rushed her to ER...dx caffiene overdose. Yep!
Anyway, back when I worked night shift. I could drink coffee all night. I'd start my shift with a Grande Vanilla Latte from Starbucks! I can't do that anymore. I miss drinking coffee.