Shares in the Danish company which makes Ozempic and Wegovy plunged 18%, as its boss warned things would get worse before they improve following steep price cuts.
Novo Nordisk had reported it expected profits and sales to fall by as much as 13%, and on Wednesday chief executive Maziar Mike Doustdar called pricing pressures "unprecedented" and "painful".
Novo said the situation had been "amplified" by a deal the firm and its rival Eli Lilly made with US President Donald Trump to lower the cost of weight-loss drugs for Americans.
The company has faced turmoil in recent months, announcing thousands of job cuts amid warnings of increasing competition and the impact of patents expiring.
Doustdar, who was appointed chief executive last summer, said he hoped the price reduction in Wegovy would be "an investment for our future" and open up access to the drug to more people.
