Shares of Tandem Diabetes Care (TNDM) plunged a staggering 33.6% in pre-market trading on Thursday, following the company's weaker-than-expected fourth-quarter results and a gloomy outlook for the current fiscal year.

The medical device maker reported an adjusted operating loss of $30.2 million for Q4, significantly wider than analysts' estimate of a $17.6 million loss. Additionally, the adjusted net loss for the quarter stood at $28.8 million, missing the consensus estimate of a $14.9 million loss. The disappointing results were primarily driven by weaker-than-expected sales and higher costs.

Exacerbating the investor concerns, Tandem Diabetes Care provided a lackluster outlook for 2025, forecasting an adjusted net loss of $1.20 per share on revenue of $1.01 billion. This guidance fell short of analysts' projections, with the revenue forecast being largely flat compared to the previous year. The company cited "muted seasonality" and "shipping delays" as factors that led to softness in demand for its insulin pumps towards the end of Q4, and expects salesforce disruptions to continue impacting the business.