The advent of continuous glucose monitoring (CGM) has been a boon to people with insulin-dependent diabetes, providing a method to keep better track of glucose levels while eliminating the discomfort of frequent finger sticks needed to self-monitor glucose levels.

CGM uses subcutaneous sensors to measure glucose levels in interstitial fluid. CGM can be done two ways: intermittently scanned (isCGM), where patients scan the sensor transmitter on demand using a receiver or their smartphone, or in real time (rtCGM), where the transmitter automatically sends glucose values to the patient's receiver or smartphone every one to five minutes, along with alerts when blood glucose levels fall outside accepted parameters.

Studies have found that both isCGM and rtCGM improve glycemic control in patients with type 1 diabetes who require multiple injections of insulin daily. However, questions remain about their use in those with type 2 diabetes and about whether patients with type 1 diabetes using isCGM would benefit from switching to rtCGM. A trio of recent studies sought to answer those questions.

In a multisite randomized controlled trial, Visser and colleagues compared the time blood glucose levels were in target range (70 to 180 mg/dL) in patients with type 1 diabetes using isCGM who then were switched to rtCGM with those who continued to use isCGM. Six months after the switch, time in range was significantly higher in patients using rtCGM compared with patients who continued to use isCGM (59.6% versus 51.9%). The patients using rtCGM also had lower glycated hemoglobin (HbA_1C) levels and reported less worry about hypoglycemic events.

In a retrospective study of 41,753 patients with insulin-treated diabetes, both type 1 and type 2, Karter and colleagues found that patients who initiated rtCGM had a 0.40% greater drop in HbA_1C levels and fewer ED visits or hospitalizations for hypoglycemia than when they self-monitored glucose levels. Those with type 2 diabetes showed greater improvement. Similar results were found in a randomized controlled trial from Martens and colleagues of the use of CGM in patients with insulin-dependent type 2 diabetes. Compared with patients using traditional blood glucose meter monitoring, those using CGM had a significantly greater decrease in HbA_1C levels (-1.1% versus -0.6%) and more time in the target glucose range.

Results of these studies provide compelling evidence of the benefit of CGM for patients with insulin-dependent diabetes, both type 1 and type 2, and the specific benefit of rtCGM. As Peek and Thomas noted in a JAMA editorial accompanying two of the studies, policy and institutional changes "that promote [CGM] in primary care will go a long way to improving diabetes control and reducing complications," particularly among disadvantaged populations with more comorbidities and high rates of complications due to poor glycemic control.-Karen Roush, PhD, RN, FNP-BC, news director