CGM in diabetes: From evidence to practice

Continuous glucose monitoring (CGM) is transforming diabetes care in both type 1 diabetes (T1D) and type 2 diabetes (T2D), with or without insulin use, said Dr Pratik Choudhary, Honorary Consultant and Professor at the University of Leicester, UK, during an Abbott-sponsored symposium at ATTD-Asia 2025 in Singapore.

He noted that clinical guidelines emphasise the importance of tools and strategies that encourage positive behaviours to enhance diabetes self-management. “This involves medication adherence, physical activity, healthy eating, and the use of diabetes technologies to achieve the best health outcomes for our patients,” Choudhary said.

CGM systems allow continuous, real-time, painless glucose monitoring 24/7, eliminating the need for frequent finger-prick tests, which can be painful.

CGM lowers HbA_1c

Compared with conventional treatment, CGM use for 26 weeks resulted in lower HbA_1c among patients with inadequately controlled T1D treated with multiple daily insulin injections. [JAMA 2017; 317:379-387]

“One thing,” said Choudhary, “is that CGM should be worn and readings reviewed as much as possible. It is an awesome tool, but it is not perfect. Patients are telling us there are too many alerts, so we need to adjust the settings.”

He pointed out that “we cannot change what we cannot measure … CGM makes the invisible visible, enabling clinicians to conduct micro-experiments. It reinforces patients’ positive behaviours, prompting action, and improves communication with the healthcare team.”

Choudhary offered simple rules for CGM use, using the acronym CHIEF – Check glucose when it helps with decisions, Inject insulin if needed, Eat, and then Forget about it.

CGM impacts lifestyle choices

A survey found that 90 percent of CGM users felt that its use supported the adoption of a healthier lifestyle. Eighty-seven percent of respondents modified their food choices based on CGM results, 47 percent reported being more likely to go for a walk or engage in physical activity after a post-meal high-glucose reading, and 42 percent increased their activity. [Clin Diabetes 2020;38:126–131]

Choudhary then presented a case of a 47-year-old male patient with T2D for 5 years and a BMI of 26 kg/m². His HbA_1c was 7.4 percent, and he was taking metformin and dapagliflozin. CGM readings showed that a high-fat meal kept his glucose elevated overnight, whereas post-meal exercise helped lower it. Additionally, a lower-carbohydrate, lower-fat evening meal flattened his overnight glucose profile.

“With the addition of smart connected pens, the patient can now see the insulin doses he’s taken and those he’s missed, helping him make decisions,” he added.

More evidence for CGM

Compared with self-monitoring of blood glucose (SMBG), CGM is superior at improving glycaemic control in individuals with T1D, particularly those with uncontrolled glycaemia. The authors reported that those with an HbA_1c of 8 percent are most likely to benefit from CGM. [Diabetologia 2022;65:604-619]

In a more recent study, both CGM and intermittently scanned CGM (isCGM) reduced HbA_1c in individuals with T2D. [Diabetes Care 2024;47:169-179] Swedish adults with T2D on insulin who used isCGM also had a significantly lower HbA_1c and fewer hospital admissions for diabetes-related complications vs those using blood glucose monitors. [Diabetologia 2025;68:41-51]

However, discontinuing CGM after 8 months in adults with T2D on basal insulin led to roughly a 50-percent reduction in the initial improvement in time in range observed with CGM use. [Diabetes Care 2021; 44:2729-2737]

Choudhary concluded his talk by urging clinicians and diabetologists to ensure the use of appropriate and safe systems. “We need to upskill and be competent in the use of these technologies to support patients and onboard others.”