BGCs can help identify subclinical hypoglycemia, but large day-today variation, in addition to hypoglycemia missed during the night, can complicate interpretation. Continuous glucose monitoring systems (CGMs) that record glucose readings over multiple days can help identify problems during the night and allow better assessment of day-to-day trends.

The FreeStyle Libre (FSL) is a CGM system that measures interstitial glucose concentration every 15 min for up to 14 days. Successful use of the FSL has been reported in both dogs and cats.^41–43 A 2019 study also reported their use in hospitalized patients with diabetic ketoacidosis.⁴⁴ Although not calibrated for veterinary patients, they appear to be generally accurate.

However, there are significant discrepancies between the FSL and AlphaTrak 2 in some patients, and variation in patients with low glucose readings may be more common and more clinically significant. Confirming low FSL glucose readings with an AlphaTrak 2, particularly when clinical signs of hypoglycemia are not evident, is recommended.

Sensors are easily placed, even in less agreeable patients, and are generally as affordable as a BGC, with significantly more useable information. FSL readers and sensors can be purchased from a veterinary distributor or from a human pharmacy. Clients should be aware that sensors do not always stay functional and attached for the full 14 days, but the information gained from even a few days of use is usually more helpful than a single BGC.