A 12-ounce can of Red Bull contains about 114 milligrams of caffeine — more than three times the amount in a 12-ounce can of Coca-Cola. Prime Energy has more: 200 milligrams in each 12-ounce can. A 16-ounce can of Bang Energy Drink, the size typically sold in convenience stores, has 300 milligrams of caffeine.

In an email response to questions, representatives for Mr. Paul, the social media personality, and Prime Energy noted that the company’s cans labeled the drink as “not recommended for children under 18.” But parents and school officials are sometimes confusing the drink with Prime Hydration, a caffeine-free sports drink from the social media stars that is sold in bottles. That drink is also immensely popular, with more than $250 million in sales in its first year and customers waiting in line for hours to buy it at some grocery stores in Britain.

“Everybody thought Red Bull was the peak of caffeine in energy drinks,” said Dr. Ryan Stanton, an emergency physician in Lexington, Ky., who said he saw patients, especially around finals weeks at local colleges, come in complaining about feeling anxious and experiencing racing heartbeats after consuming too much caffeine. “Now, some of these drinks have two or three times the level of caffeine as Red Bull.”

Studies have shown that consuming caffeine may have health benefits, but that too much could result in cardiovascular and gastric issues. The Food and Drug Administration has investigated a handful of reports over the years involving people dying shortly after consuming energy drinks or five-hour energy shots. But the agency has never established a link between the two, a spokesman for the F.D.A. said in a response to emailed questions.

Adults are recommended to have no more than 400 milligrams of caffeine per day. Pediatricians recommend that youths ages 12 to 18 should not consume more than 100 milligrams of caffeine per day and that children under 12 should avoid caffeine completely.