The reports were first detailed by the New York Times on Wednesday.
The news follows the FDA's disclosure last month that it was investigating reports of five deaths that may be related to Monster Beverage's namesake drinks.
The highly caffeinated beverages are the fastest-growing type of soft drink in the United States, with sales increasing 17 percent last year to about $9 billion, according to Beverage Digest.
FDA spokeswoman Shelly Burgess said that 5-hour Energy, sold by Living Essentials, has been mentioned in some 90 FDA filings since 2009, including more than 30 that involved serious or life-threatening events like heart attacks, convulsions, and in one case, a spontaneous abortion, the New York Times reported.
The Times said another federal agency, the Substance Abuse and Mental Health Services Administration, reported late last year that more than 13,000 emergency room visits in 2009 were associated with energy drinks alone.
But Elaine Lutz, spokeswoman for Living Essentials, the company that distributes 5-hour Energy, said in a statement that the product "is not an energy drink" (the so-called shot comes in a bottle that holds less than 2 ounces).
"Living Essentials," the statement went on, "takes reports of any potential adverse event tied to our products very seriously. We fully comply with all of our reporting requirements." The company was "unaware of any deaths proven to have been caused by the consumption of 5-hour Energy."
Currently the FDA does not publicly disclose adverse event filings about dietary supplements, including energy shot drinks.