From espresso shots to energy gum, it seems as though caffeine comes in many forms these days. Promising two times more caffeine than regular coffee, Death Wish is an "extreme" coffee brand dubbed as "the world's strongest coffee."

A regular 16-ounce cup of coffee has about 320 milligrams of caffeine, according to the American Beverage Association.

"Death Wish Coffee is the most highly caffeinated premium dark roast organic coffee in the world. This is Extreme Coffee, not for the weak. Consider yourself Warned," the website says.

Regular coffee is made with Arabica beans that have a mild flavor. Made with fair-trade Robusta beans that are organically grown, Death Wish coffee beans are dark roasted to help soften their stronger flavor.

If the coffee has double the amount of caffeine per cup, and if the standard is 16 ounces, "That means that Death Wish is giving 660 mg. Case reports have shown toxicity at about 700 mg," said Dr. John Spangler, professor of family medicine at the Wake Forest School of Medicine in Winston-Salem, N.C.

Spangler referred to two cases in which the patients suffered from acute caffeine intoxication and low potassium after taking herbal supplements.

The company's Facebook page has loyal fans and tons of requests for the product.

"I'd say one cup of this is comparable to about 5 shots of espresso … but with an outstanding taste, no cream, sugar, or anything of the like necessary. I felt like superman on steroids. Welp, off to save the world folks!" Diedrick Nagle wrote on the Death Wish testimonial page.

The company is so confident in the potency of its product that it offers to buy it back if you find a stronger product. It costs $19.99 per pound, compared to the average coffee bag, which is less than $10.

Phil Broughton, a UC-Berkeley radiation-safety expert, made Death Wish even stronger and documented it on his blog. Broughton created a concentrate through a cold-water steeping and vacuum extraction that he called Black Blood of the Earth (BBotE.)

BBotE has about 40 times the amount of caffeine in coffee. No more than one shot at a time is recommended. A 750-milliliter bottle of BBotE is sold on his website for $40.

(Image Credit: Death Wish Coffee)