According to a letter from the FDA, there have been two deaths and one suicide among patients who used products containing semaglutide - the active ingredient in both Ozempic and the weight-loss drug Wegovy.
The FDA has not determined that the deaths or other suspected side effects were actually linked to taking the company's drug.
Novo Nordisk, which has been losing market share to U.S. arch-rival Eli Lilly for some time, says it will address the FDA's remarks quickly and from a holistic perspective.
Novo Nordisk shares, which have lost more than half of their value in a year, are down more than 2 percent after the FDA warning was reported.
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