One time I accidentally drank 1200mg of caffeine.
I bought a bunch of Celsius energy drinks in various flavors when they first came out and brought them home on the way to a party, thinking I'd store them in the fridge there and drink them the next morning. The party started, and I got tipsy, forgetting they were caffeinated. So I mixed them up with seltzers, drank all of them, and had a lot of alcohol. It felt great while the alcohol was still effective because they complemented each other.
I had a relaxed energy for a while, but then I got a strange urge to walk home at 2 a.m. I left without telling anyone and walked halfway across the city. No one bothered me, but I probably looked like an insane tweaker (which I basically was).
When I got home I curled up in bed, but I wasn't sleepy. My husband called me, asking where I'd been, which was fair. I told him I'd walked home, which he surprisingly took in stride (we both have pretty significant mental illnesses so we're somewhat used to each other doing odd shit sometimes). But then he asked about the energy drinks, and I said I didn't know what he was talking about. Then I checked my pulse, and it hit me.
I looked up the LD50 value for caffeine, which was like 10 times more than I'd consumed, plus I take propranolol as-needed for anxiety so I just took some of that too and was more or less ok. But the next six hours were spent in bed under a fan, tossing the blanket on and off, and occasionally running to the bathroom to shit straight liquid.
It was almost as bad as the time I took 300mg of THC as a first-time user who'd never even smoked before.️