Would you pay $19 a pound for a coffee bean that is more than twice as strong as Starbucks’ dark roast? Customers in 22 countries around the world are answering that question with a resounding “yes!”

Unfortunately, that choice could have unintended consequences, including heart palpitations, experts say.

“Black Insomnia,” dubbed the world’s strongest coffee, is now available in the United States. Just one cup will put you over the daily recommended caffeine limit.

"If you want to stand out, you need to be the 'est' — the biggest, smartest, strongest, or cheapest," said Black Insomnia founder Sean Kristafor. "So when we wanted to compete in coffee, as a caffeine product, we had to be the strongest, but obviously, we don't exceed the world guidelines."

Black Insomnia started in South Africa and has since caught on across the globe, now selling five to six tons of coffee a month. The company uses the “robusta” bean, which Kristafor has tested chemically against his competitors.

Black Insomnia contains 58.5 milligrams of caffeine per fluid ounce, while Starbucks’ dark roast packs 21.25 mg. A shot of black insomnia is within the Food and Drug Administration’s recommended limits for daily caffeine consumption. But a large cup — which could be 702 mg of caffeine — is way over the FDA threshold of 400 mg of caffeine daily.

"For the same amount of coffee, you will get double the amount of caffeine," said Mary Sweeney, who researches the effects of caffeine at Johns Hopkins School of Medicine.

"This makes it easier to consume more caffeine than you intend to and effects can range from mild to severe, for example, jitteriness, nervousness, restlessness and trouble sleeping. The most serious effect would be cardiac arrhythmia (irregular heartbeat)."

Experts note that it’s not just Black Insomnia that may contribute to such symptoms. Simply drinking too much regular coffee can have those effects as well.

Ted Kallmyer, editor of consumer information site Caffeine Informer, says the amount of caffeine in Black Insomnia is still much higher than what most experts would recommend for daily consumption.

“This group of people has, over time, built up their caffeine tolerance and/or their livers process caffeine really well so it doesn’t affect them adversely,” he says. “However, the problem with these products is that they can inadvertently be consumed by people who are not in the targeted category.”

Kristafor says he and his team are very aware of the limits to drinking Black Insomnia and points out that there are clear warnings on the labels.

"On Caffeine Informer, they say that if you drink more than 20 cups of Black Insomnia, you win the Darwin Award ... an award for people who pass away for doing stupid things."

Black Insomnia isn’t the only brand in the hyper-caffeinated space. The makers of Death Wish, whose coffee is 54.2 mg of caffeine per fluid ounce, says they’re not scared of the new competition.

"We're the leader in the strong coffee category and are not letting up anytime soon. Our coffee is much different than the competition, due to the fact that our roast is USDA [U.S. Department of Agriculture) Certified Organic and Fair Trade Certified as well,” Caiden Tuller, who works customer service for the company said.

Amazon sells both products. The commerce company requires all the products it carries to follow Food and Drug Administration regulations.

That includes accreditation of the roasting facility, packaging and labeling. But the FDA considers caffeine a natural chemical — not a nutrient. If caffeine is added separately, then it has to be listed on the product label.