Guidelines on GLP1RAs and Continuous Glucose Monitors are Among Biggest News in Diabetes

Irl B. Hirsch, MD


August 30, 2022

Many changes in the evolution of the treatment of diabetes have occurred during this year and 2021. Randomized controlled trials have resulted in updated guidelines for the use of new medications and changing technologies. This has included the use of glucagon-like-receptor agonists (GLP1RAs) and sodium-glucose co-transporter-2 inhibitors (SGLT2 inhibitors) for the treatment of cardiovascular disease and renal disease, in addition to the use of continuous glucose monitoring (CGM) to better manage glycemia. I am hoping my discussion about these major advances in this edition of Highlights will be helpful to those caring for patients with diabetes.


Irl. B Hirsch, MD

The first GLP1RA, exenatide, was released in April 2005. Since then, numerous daily and weekly drugs of this class have been developed. We’ve learned they are effective glucose lowering drugs, and the weekly agents dulaglutide and semaglutide have shown impressive weight reduction properties as well as cardiovascular benefits.

Secondary outcomes have also shown renal benefits to these agents, and studies for primary renal efficacy are pending. Due to all of these properties, the GLP1RAs are recommended as the first injectable for the treatment of type 2 diabetes, prior to insulin initiation.[1]

The next generation of these agents are a combination of a GLP1RA and a glucose-dependent insulinotropic polypeptide (GIP). GLP-1 stimulates insulin secretion, inhibits glucagon secretion, delays gastric emptying, and has central effects inducing satiety.

We now understand that GIP is the main incretin hormone in those without diabetes, causative of most of the incretin effects. But the insulin response after GIP secretion in type 2 diabetes is strongly reduced. It is now appreciated that this poor effect of GIP can be reduced when used in combination with a GLP1RA. This combination incretin, called by some a “twincretin,” is the basis for the drug tirzepatide which was approved by the Food and Drug Administration in May of 2022.

The data supporting this agent for both diabetes and obesity are impressive. For example, in a 40-week study with a baseline HbA1c of 8.0%, those randomized to tirzepatide at 5 mg, 10 mg, and 15 mg had HbA1c reductions of 1.87%, 1.89%, and 2.07% respectively.[2] Over 81% at all doses had HbA1c levels less than 6.5% at 40 weeks.

For the 5-mg, 10-mg, and 15-mg doses, weight change from baseline was 7.9%, 9.3%, and 11.0% respectively. Like older GLP1RAs, gastrointestinal side effects were the main problem. For the three doses, 3%, 5%, and 7%, respectively, had to stop the drug, compared with the 3% who stopped taking the placebo. In another study, tirzepatide was noninferior or superior at all three doses compared with semaglutide 1 mg weekly.[3]

In a population without diabetes, with 40% of patients having prediabetes, weight loss percentages for the three doses were 15.0%, 19.5%, and 20.9% respectively.[4] Discontinuation percentages due to side effects were 4%-7%. The exciting part is we now have a drug that approaches weight loss from bariatric surgery. The cardiovascular and renal outcome trials are now underway, but the enthusiasm for this drug is clear from the data.

Like other GLP1RAs, the key is to start low and go slowly. It is recommended to start tirzepatide at 2.5 mg four times a week, then increase to 5 mg. Due to gastrointestinal side effects, some patients will do better at the lower dose before increasing. For those switching from another GLP1RA, there are no data to guide us but, in my practice, I start those patients at 5 mg weekly.

Continuous glucose monitoring

Data continue to accumulate that this form of glycemic self-monitoring is effective to reduce HbA1c levels and minimize hypoglycemia in both type 1 and type 2 diabetes. The most important change to the 2022 American Diabetes Association (ADA) standards of care is recognizing CGM as level A evidence for those receiving basal insulin without mealtime insulin.[5] There are four CGMs on the market, but most of the market uses the Dexcom G6 or the Libre 2. Both of these devices will be updated within the next few months to newer generation sensors.

While there are similarities and differences between the two devices, by late 2022 and early 2023 changes to both will reduce the dissimilarities.

The next generation Libre (Libre 3) will be continuous, and “scanning” will no longer be required. For those who don’t have insurance coverage, the Libre will continue to be more affordable than the Dexcom. Alerts will be present on both, but the Dexcom G7 will be approved for both the arm and the abdomen. The Dexcom also can communicate with several automated insulin delivery systems and data can be shared real-time with family members.

For clinicians just starting patients on this technology, my suggestion is to focus on one system so both the provider and staff can become familiar with it. It is key to review downloaded glucose metrics, in addition to the “ambulatory glucose profile,” a graphic overview of daily glycemia where patterns can be identified. It is also helpful to ask for assistance from endocrinologists who have experience with CGMs, in addition to the representatives of the companies.

COVID-19 and new-onset diabetes

From the beginning of the COVID 19 pandemic in 2020, it was clear that stress hyperglycemia and glucose dysregulation was an important observation for those infected. What was not known at the time is that for some, the hyperglycemia continued, and permanent diabetes ensued.

In one study of over 2.7 million U.S. veterans, men infected with COVID-19, but not women, were at a higher risk of new incident diabetes at 120 days after infection compared to no infection (odds ratio for men = 2.56).[6]

Another literature review using meta-analyses and cross-sectional studies concluded new-onset diabetes following COVID-19 infection can have a varied phenotype, with no risk factors, presenting from diabetic ketoacidosis to milder forms of diabetes.[7]

The current thought is that COVID-19 binds to the ACE2 and TMPRSS2 receptors which appear to be located on the beta-cells in the islet, resulting in insulin deficiency, in addition to the insulin resistance that seems to persist after the acute infection. Much more needs to be learned about this, but clinicians need to appreciate this appears to be a new form of diabetes and optimal treatments are not yet clear.

Dr. Hirsch is an endocrinologist, professor of medicine, and diabetes treatment and teaching chair at the University of Washington, Seattle. He has received research grant support from Dexcom and Insulet and has provided consulting to Abbott, Roche, Lifescan, and GWave. You can contact him at

This article originally appeared on, part of the Medscape Professional Network.

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