In short, it would take at least six gallons of McDonald's coffee. In April, a coroner's report cited a New Zealand woman's consumption of Coca-Cola as being related to her death. But she reportedly had a number of other unhealthy habits, including smoking cigarettes and a poor diet.
But as Popular Science notes, individual reactions to caffeine intake vary from person to person and are heavily influenced by a number of other factors, including related health issues and the consumption of other substances, such as alcohol.
The Journal of Caffeine Research editor-in-chief Jack James tells PopSci that it takes "about" 10 grams of caffeine to achieve lethal levels. According to the Mayo Clinic, the average adult can safely consume 200 mg to 300 mg of caffeine per day, the equivalent of about 2 to 4 cups of coffee.
However, consuming more than 500 mg per day can begin to trigger side effects, including insomnia, fast heartbeat and muscle tremors.
You can read more of this article here.