Tandem's t:slim X2 speaker wiring can stop insulin delivery mid-use

In July and August 2025, Tandem Diabetes Care issued a voluntary medical device correction for select t:slim X2 insulin pumps. A wiring issue with certain pumps' speakers could trigger an error presenting as a 'Malfunction 16' alarm that stops insulin delivery and terminates communication between the pump, the continuous glucose monitor and the companion app.

The consequence was loss of insulin and of live glucose data, with a risk of hyperglycemia severe enough that some patients required medical intervention. By the time of the announcement Tandem had tallied 700 confirmed adverse events, 59 reported injuries and no deaths.

Tandem said it notified customers starting 22 July 2025, would release a software update for early detection of speaker failure and persistent vibration alerts, and asked users to complete the update when notified. The FDA posted the correction on 12 August 2025.

The decision under review was a component's failure mode reaching production: a cheap speaker whose wiring could fail in a device patients rely on to stay alive, caught only after hundreds of adverse events rather than in design review.