Ask the Doctors: CGM a useful tool for tracking blood glucose in real time

Dear Doctors: My best friend has diabetes. She used to do finger sticks, but now she has a wearable glucose monitor. How do they work? It’s got me wondering if it might be a good idea for me to use one, too. I’m 66, and, as I’m getting older, I worry more about developing Type 2 diabetes.

Dear reader: The risk of developing Type 2 diabetes increases with age. People who are 45 or older, overweight, sedentary or have a family history of diabetes are at increased risk.

Other contributing factors include poor diet, poor sleep and metabolic issues tied to insulin resistance.

Your concern about keeping your blood sugar within a healthy range is well-founded.

A continuous glucose monitor, also known as a CGM, is a wearable medical device that allows someone to track blood-sugar levels in real time. A tiny filament implants into either the upper arm or the belly and sits in the tissues just below the skin. It’s attached to a wireless transmitter that sends the data to the device.

Depending on the brand, that data can be read on a cellphone app, a smart watch or a dedicated receiver. Some CGM devices can be applied by the user at home. Others require a visit to a health professional. The length of time a sensor is meant to remain embedded ranges from a few days to a few months.

The sensor measures glucose levels in the cellular fluid where it is implanted. Unlike a finger stick, which requires a separate test for each new data point, a CGM lets you track blood-glucose levels in real time. That means you’re easily able to see how your body responds to different foods, periods of fasting and various types and levels of activity.

A CGM offers a more complete picture of how your body manages blood sugar throughout the day and night. While these devices can greatly reduce the need for finger sticks, they have not replaced them. Blood-based glucose readings are the gold standard for accuracy. They continue to be recommended for CGM users.

Though most CGM users have diabetes, we sometimes recommend the 14-day variety for certain non-diabetic patients as a one-time learning exercise. Seeing how specific foods and activities affect blood sugar helps them make more informed choices. Your doctor can help you decide if this would be useful for you.

Dr. Eve Glazier and Dr. Elizabeth Ko are internists at UCLA Health.