Getting annoyed at those 5-Hour Energy commercials, I decided to do a little research. Might interest people to know that the drink boasts that it contains 2000%-8333% the daily recommended values of some vitamins. Some comparisons: it contains 30mg of B3 while the recommended daily value is 6mg, B6—40mg vs recommended 0.8mg, and 500mcg of B12 vs the recommended 2.4mcg. 5-Hour claims that these surpluses are safe, because the vitamins are water-soluble, and your body will easily flush them out. However, to flush out excess solutes like this, your body requires excess water, which most people don’t get.
Guess what? Contrary to what the 5-Hr Energy website so confidently boasts, it IS possible to overdose on these vitamins. Toxic levels can be indicated by numb hands and feet, headaches, dizziness, fainting, jaundice (yellowing of skin and/or eyes that indicates liver failure), and in extreme cases can also cause temporary nerve/brain damage.
Perhaps one shot ever now and then is safe, provided one drinks plenty of water— but it IS UNSAFE to consume more than one a day, or to take one daily for many consecutive days.