That jittery feeling is a sign to change course, not panic. Drinking too much coffee can overstimulate your nervous system, leading to jitters, anxiety, digestive upset, a racing heart, and sleep ...

While everyone’s tolerance is different, there is a limit to how much caffeine people can have in their systems. Jittery fingers and a racing heartbeat are common signs that you’re over-caffeinated.

Nick Blackmer is a librarian, fact-checker, and researcher with more than 20 years of experience in consumer-facing health and wellness content. Experts recommend capping your caffeine intake at 400 ...