Is a Continuous Glucose Monitor Right for Me?

By Mary Ann Kliethermes, PharmD

If you have diabetes, you know that testing your blood sugar — also called blood glucose — is an important tool for managing the condition. A blood sugar meter and disposable test strips can be used at home to measure the amount of sugar in a drop of blood. Another testing option is a continuous glucose monitor (CGM), which measures blood sugar every few minutes using a sensor inserted under your skin. Your pharmacist can help you choose a testing method that’s right for you.

What is a CGM?

A CGM includes a tiny sensor, inserted just beneath your skin, that measures sugar levels in the surrounding fluid every 1 to 5 minutes. The sensor transmits readings wirelessly to a receiver, smart phone, or other compatible device. This allows people with diabetes to view and share their sugar levels.

What is the difference between checking your blood sugar with a finger stick and using a CGM?

The CGM operates continuously, day and night, to sense and track sugar levels in the fluid surrounding the skin cells. A finger-stick test provides a single blood sugar measurement at the time of the test.

CGMs enable people to view trends and get immediate alerts if sugar levels are too high or too low. Most people who have diabetes know that their sugar level varies throughout the day in response to meals, physical activity, and medication use, especially insulin therapy. Undetected blood sugar fluctuations can cause symptoms that are uncomfortable and hard to manage.

CGMs allow you to respond to blood sugar fluctuations before symptoms develop. Continuous monitoring of blood sugar levels and patterns can improve your care, support your personalized diabetes-management plan, and keep your blood sugar level within your desired range.

There are two types of CGMs

Real-time continuous glucose monitors:

• These monitors transmit real-time information about your sugar to a receiver or smartphone application.
• Most sensors require replacement after 7–14 days; one product has a 90-day maximum wear time before replacement.

Intermittently scanned continuous glucose monitor:

• This monitor’s transmitter works with a separate scanner to send blood sugar data to a reader.
• Scanning should be done at least once every 8 hours.
• The sensor must be replaced every 14 days.

What are the benefits of CGMs?

Continuous monitoring of sugar levels allows your doctor or pharmacist to fine-tune the timing or dosage of diabetes medications to reduce blood sugar level fluctuations. This especially benefits people who don’t realize that their blood sugar is too high (hyperglycemia) or too low (hypoglycemia). CGMs can also help you track the real-time effects of exercise and meal choices on blood sugar levels. With this knowledge, your healthcare providers can help you adjust your activities, medications, and diet to meet your blood sugar goals.

Some CGM systems sound an alert if your sugar level becomes too high or low or show a visual warning if the level is trending up or down. Parents, caregivers, and your healthcare team can receive alerts and other data on their smart devices and provide extra support in managing your diabetes.

CGM systems can reduce but not eliminate the need for finger-stick tests. If you have symptoms of high or low blood sugar that aren’t consistent with your CGM reading, you should perform a finger-stick test to confirm the results. Daily finger-stick blood sugar testing may also be required to calibrate the CGM system.

How do the results from CGMs compare to results from monitoring glycosylated hemoglobin (HbA1_c)?

HbA1_c values reflect your average blood sugar over the past three months by measuring the sugar concentration in your red blood cells. Your HbA1_c value, together with data from your CGM, indicate how well your diabetes is managed. Using a sugar concentration goal of 70–180 mg/dL, CGMs report your time above, below, and within that range.

Ideally, your sugar level is within range at least 70% of the time that you wear the sensor. CGMs also provide an estimated HbA1_c value over the wear period and a graph showing daily glucose levels and trends. Data from your CGM, along with periodic HbA1_c, tests, can be used to adjust your diabetes-management plan and better control your blood sugar.

Who may benefit from a CGM?

Continuous glucose monitors are approved by the Food and Drug Administration for children and adults with type 1 or type 2 diabetes. CGMs are also beneficial for people with prediabetes and are approved for women with diabetes associated with pregnancy.

How do CGMs work?

CGMs usually consist of three parts:

1. A sensor with a tiny wire is placed under your skin on your belly or arm. An adhesive patch holds the sensor in place on your skin.
2. A transmitter connected to the sensor wire sends blood sugar readings wirelessly to your smart phone or reader device. Some transmitters are attached to the sensor and disposed with it at the end of the wear period. Other CGMs have a reusable transmitter that must be attached to the new sensor at replacement time.
3. Your smart phone or reader can display your current sugar level and your sugar levels over time. Some CGM devices can transmit the readings to your insulin pump.

Summary

CGM systems are helpful tools to improve diabetes care, especially for people who struggle to manage their blood sugar. CGMs provide real-time information and show trends that aren’t apparent from periodic finger-stick testing.

Your pharmacist and your other healthcare providers can help you choose a CGM that may be best for you. They can also help you develop an individualized plan of care to achieve your personal diabetes-management goals.