The Ins and Outs of a Continuous Glucose Monitor

Written by Stephanie Thurrott, interview quotes and information provided by Jordan R. Wagner BSN, RN, CDCES

If you have diabetes, you know how important it is to keep a close eye on your blood glucose levels. A continuous glucose monitor (CGM) could help you get tighter control over your blood sugar and spot worrisome spikes or drops before they reach dangerous levels. Jordan Wagner, a diabetes educator at Banner University Medical Center - Phoenix, knows firsthand how helpful these monitors can be. As someone who is living with type 1 diabetes himself, he uses a CGM. Here, he explains what CGMs are, how they work, and why they can give you better information than fingerstick blood tests.

Continuous glucose monitors give you detailed data

After your doctor prescribes a CGM, you insert a small sensor under your skin, usually on your abdomen or the back of your arm, in the comfort of your own home. The sensor reads glucose levels from the fluid just outside your cells and transmits it to a receiver or to your cell phone every five minutes. “This data allows you to see trends in your sugars, which is very valuable for figuring out where the ‘problem’ spots are in your sugar control,” Wagner said. A CGM tracks your glucose levels 24/7 for seven to 14 days. (Some people may qualify for a 90-day monitor.)

The value in a wider view of your blood sugar

“CGMs give you the advantage of being able to see the trends of your blood sugar at all hours of the day,” Wagner said. He compared it to the difference between a photo and a video. A typical glucose check is like a photo—it’s a snapshot of one point in time. The CGM shows you not only what your glucose level is, but whether it’s going up, going down, or holding steady. Your doctor or diabetes educator can teach you how to make better decisions about your diabetes control with the information you get from your CGM. You can set target ranges for your sugar levels, and your CGM data can tell you how often you are within those targets. The CGM can help you identify problems spots with your glucose control so you can come up with a game plan to address them.

Information you can use to make decisions

CGM data can also help you make more informed decisions about managing your diabetes. “For example, imagine checking your blood sugar with a finger stick before driving and it comes back at 120. You might be thinking ‘that’s a great number.’ But if your CGM showed 120 and that your sugar level was rapidly dropping—now that’s a different story,” Wagner said. “That would tell you that it’d be a good idea to confirm with a fingerstick, have a snack and wait for your sugar to stabilize before driving. It could potentially save your life!”

Wagner said knowing his CGM monitors his glucose throughout the night and would alert him if his levels are getting low gives him peace of mind. “I used to have an uneasy feeling at bedtime that I might have low blood sugar in the middle of the night, as one of my family members passed away from a low at night. Since wearing a CGM, I no longer have this feeling and my glucose levels have been consistently controlled,” he said.

His CGM also helps him know if his sugar is getting low during strenuous exercise like running. “This allows me to take a break, have a snack and start running again in no time,” he said.

Is a continuous glucose monitor right for you?

Many people with type 1 and type 2 diabetes qualify for a CGM with a doctor’s prescription, and the FDA has approved certain sensors for insulin-based decisions. With some CGMs, you can replace fingersticks almost completely. If you feel symptomatic it’s best to check your sugar with a fingerstick and treat it accordingly though, Wagner said, since CGMs can sometimes record rapid changes inaccurately. Some conditions, such as chronic anemia, dehydration, and certain medications, might cause faulty readings in your CGM. It is best to talk with your doctor about trying a CGM and see if it is right for you.