The affected cartridges may be at risk for leaking. This could potentially result in the device delivering too much or too little insulin, which can lead to a serious adverse event.

Tandem president and CEO Kim Blickenstaff noted the safety of the company’s customers is its top priority.

"For that reason, even after our previous announcement Tandem’s team continued to perform further testing. Based on this work we recognized that additional cartridge lots could also be at risk for leaking and so we are expanding the scope of this recall.

"We are confident that we have identified all of the affected cartridge lots that may have been shipped to customers or distributors and that we have implemented appropriate corrective actions to prevent this from happening in the future," Blickenstaff added.

The affected lots shipped to customers or distributors represent an aggregate of approximately 13,000 boxes of cartridges (10 cartridges per box). The affected lots announced on 10 January 2014 were shipped from 17 December 2013 to 10 January 2014. The affected lots announced on 20 January 2014 were shipped prior to 16 October 2013.

All other cartridge lots shipped to customers or distributors and the t:slim insulin pump are not affected by this recall.

The Company has determined that under certain conditions a specific piece of equipment used in the cartridge test process caused the affected cartridges to be at risk for leaking. Tandem has already implemented modifications to the cartridge manufacturing test process to prevent this issue from occurring in the future, and the Company’s manufacturing facility is able to support ongoing customer demand.

The company is working with its customers and distributors to replace cartridges subject to the recall. Based on the periods during which the affected lots were shipped, the company believes a significant number of the affected cartridges have already been used and therefore will not be exchanged.

In addition to the expenses associated with replacing affected cartridges, the company may also incur additional logistical shipping fees and other recall coordination costs. Tandem is also in the process of evaluating additional cartridges still in the company’s internal inventory to determine whether they will be usable, and may incur expenses with those that are unusable.