Tandem Diabetes Care Inc. experienced a significant 24-hour plunge of 7.04% in extended trading, following the company's announcement of a proposed private placement of convertible senior notes.

The insulin pump maker revealed plans to offer $200 million in convertible notes due 2032, with an option for initial purchasers to buy up to an additional $30 million. This capital raising move typically creates downward pressure on stock prices due to investor concerns about potential dilution when the notes are converted into shares and the increased debt burden on the company's balance sheet.

The offering announcement comes after the stock had shown strong performance recently, having closed up 15% in the previous trading session and jumping 33% last Friday following better-than-expected fourth-quarter results. The company plans to use the net proceeds for general corporate purposes, including potential acquisitions, strategic investments, working capital, and operating expenses, while also allocating a portion to fund capped call transactions designed to help offset potential dilution.