How many mg of caffeine is enough to induce a dangerous arrhythmia within a 24 hour period?

Depends on sensitivi: Answer depends on your own personal body composition & sensitivity to caffeine. (Are you genetically a slow caffeine metabolizer? Were you ever tested?). The human LD50 (amount to make 50% of us die) from caffeine is estimated to be ~150-200 mg/kg of body mass or roughly 40-50 mugs of coffee for an average adult. Though achieving lethal dose of coffee is difficult, be wary of caffeine pills!