It’s not likely that you could eat so much chocolate to suffer from theobromine toxicity. A toxic dose in humans is 1,000 milligrams (or 1 gram) of theobromine for each kilogram of body weight. For someone weighing 150 pounds, that’s 68,000 milligrams (68 grams) of theobromine.
An ounce (28 grams) of dark chocolate with 70 to 85% cacao has 227 milligrams of theobromine and 23 grams of caffeine. To eat enough chocolate to have theobromine toxicity, you’d need to eat 300 ounces of chocolate. That’s 764 squares of Ghirardelli chocolate or 85 Lindt Excellence chocolate bars. Eating just half that might make you sick just from the caffeine because 150 ounces of that same chocolate will put 3,450 milligrams of caffeine in your system. That’s like drinking 34 cups of coffee in a single sitting.
Milk chocolate doesn’t have as much theobromine or caffeine as dark chocolate. A standard 1.5-ounce milk chocolate bar has 90 milligrams of theobromine and about 9 milligrams of caffeine. Theobromine could reach toxic levels in your system if you eat about 755 chocolate bars.