"The amount you said is not toxic for an adult, or likely even for a
child. The LD50 dose is 525 mg for every kilogram of your body weight.
But in English/American units, this turns into about 240 mg for every
pound of your body weight. If you are over 100 pounds in weight, then
you would need over 24000 mg of lithium carbonate to be at the LD50
dose. Incase you don't know, "LD50" means the amount of toxic
substance required for you have a 50/50 chance of being killed."
Looks like that substance would take a zillion pills for you to
overdose on it. You would need to ingest something like 500 pills.
That's crazy dude.