What Happened?

Shares of diabetes technology company Tandem Diabetes Care (NASDAQ: TNDM) jumped 20.3% in the afternoon session after the company reported third-quarter results that surpassed analyst expectations for both revenue and earnings per share. 

For the quarter, Tandem posted revenue of $249.3 million, a 2.2% year-over-year increase, which was well ahead of the consensus estimate of $236 million. The company's loss per share came in at $0.31, narrower than the $0.32 loss that analysts had predicted. The results were also bolstered by an improvement in operational efficiency, as the company's operating margin increased to -9.2% from -10.7% in the same period a year ago. Overall, it was a strong quarter that significantly exceeded Wall Street's expectations.

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What Is The Market Telling Us

Tandem Diabetes’s shares are extremely volatile and have had 42 moves greater than 5% over the last year. But moves this big are rare even for Tandem Diabetes and indicate this news significantly impacted the market’s perception of the business.

The previous big move we wrote about was 1 day ago when the stock dropped 5.1% on the news that analyst projections for its third-quarter 2025 earnings pointed to a year-on-year revenue decline. For the quarter, analysts expected revenue to fall 3.3% to $236 million, a sharp reversal from the 31.4% increase the company posted in the same period of the previous year. The company was also projected to report an adjusted loss of $0.34 per share. Compounding these concerns, the company had missed Wall Street's revenue estimates twice over the past two years. This outlook followed a challenging period for the company, which in August 2025, had announced a voluntary medical device correction for some of its t:slim X2 insulin pumps due to a speaker-related issue.

Tandem Diabetes is down 54.7% since the beginning of the year, and at $16.24 per share, it is trading 56.7% below its 52-week high of $37.53 from January 2025. Investors who bought $1,000 worth of Tandem Diabetes’s shares 5 years ago would now be looking at an investment worth $154.97.

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