How much caffeine is too much?

Mayo Clinic reports 400mg a day as a safe amount for healthy adults.

Mayo Clinic reports 400 mg a day as a safe amount for healthy adults.

When I heard on the news that an 18 year old had died from a caffeine overdose, the image that immediately came to mind was a stack of empty energy drinks.  That, however, is not what happened.  The high school senior had consumed a teaspoon or more of powered caffeine, 16 times the recommended dose.

The Mayo Clinic reports 400 milligrams of caffeine a day as a safe amount for healthy adults.  Adolescents should consume no more than 100 mg.

To put this into perspective, check out these numbers from Consumer Reports:

5-hour Energy Extra Strength 242 milligrams
Rockstar Energy Shot 229 milligrams
NOS High Performance Energy Drink 224 milligrams
Monster X-presso 221 milligrams
Full Throttle 210 milligrams
8 oz cup of StarBucks coffee 165 milligrams
Monster Energy 92 milligrams
Red Bull Energy Drink 83 milligrams
Standard cup of coffee 100 milligrams


Basically these are saying that if you consume two or more of the high end energy drinks you are way over the recommended safe amount and are putting yourself at risk.  The same for four or more cups of regular coffee.

According to WebMD caffeine works by stimulating the central nervous system (CNS), heart, muscles, and the centers that control blood pressure.  If you take too much, blood vessels can constrict, decreasing blood flow to the heart.  This can result in the following symptoms:

  • Insomnia
  • Nervousness
  • Restlessness
  • Irritability
  • Stomach upset
  • Fast heartbeat
  • Muscle tremors

A large dose of caffeine can result in heart attacks and seizures.  That’s what happened to the high school senior.  His autopsy revealed he had died of seizures and cardiac arrhythmia, or an abnormal heartbeat, brought on by a caffeine overdose.

So this week, as you reach for that Monster or cup of joe, take a moment to consider how much caffeine you’ve consumed.  Perhaps it’s time for decaf….

Submitted by Tina Comston, M.Ed.

Reviewed by Mary Lynn Kiacz, MD