The FDA’s release of a warning letter sent Dexcom Inc. (NSDQ:DXCM) this month reveals that the glucose monitoring company failed to report at least 4 incidents of low blood sugar requiring medical attention and at least 1 instance in which the device shocked a patient.

Dexcom disclosed the March 14 warning letter earlier this week, saying only that the letter flagged "deficiencies in filing medical device reports (MDRs) involving the company’s continuous glucose monitoring system."

The warning letter, published yesterday by the FDA, shows that San Diego-based Dexcom received 4 reports of "events where patients sustained an injury (i.e. hypoglycemia) while using your firm’s device. The patients were treated with glucose tablets or glucagon." The watchdog agency inspected Dexcom’s facility from Oct. 30, 2013, through Nov. 7, according to the letter.

"The referenced medical interventions to treat hypoglycemia are considered medical interventions necessary to preclude permanent impairment or a body function or permanent damage to a body structure. Your firm did not submit an MDR for each referenced event," according to the letter.

Dexcom also received a report that "reasonably suggests that your firm’s device malfunctioned (i.e. electrical shocks)," according to the letter.

"There is no information in your firm’s complaint file to justify why the referenced malfunction would not be likely to cause or contribute to a reportable death or serious injury, if it were to recur. Your firm did not submit an [medical device report] for the referenced event," according to the letter.

The FDA said it can’t determine whether Dexcom’s response to the problems found during the inspection is adequate. The company said it plans to be in compliance with FDA rules by the end of April.

"The adequacy of your firm’s response dated November 26, 2013, cannot be determined at this time. The response indicates that actions will be completed in the future to include a revised MDR procedure and retrospective review of complaints and submission of MDRs to FDA. No evidence of completion for the proposed actions were included in your firm’s response. Without this documentation in hand we cannot determine the adequacy of your firm’s response," according to the letter.