What are the disadvantages of blinded continuous glucose monitoring?

There are some disadvantages to blinded continuous glucose monitoring (CGM). With blinded CGM, the person with diabetes wears a CGM device for three to five days but cannot see any glucose values until meeting with a healthcare provider after the monitoring period. No alarms will go off, even if the glucose value is extremely high or dangerously low. The person will not see trend arrows and will be unable to see how food, exercise, stress and other factors affect diabetes control. 
Steven Edelman, MD
Endocrinology Diabetes & Metabolism
Blinded continuous glucose monitoring (CGM) may be a disadvantage to people with diabetes. Why would you not want to see your blood sugar numbers? Why would you not want to be alerted to high or low measurements? Why would you not want to see the effects of how different types and amounts of food affect your blood sugar? Why would you not want to see how exercise affects your diabetes control? Are our lives so predictable that those three days of blinded CGM represent the norm -- and we never have days where our meals and activities are different than usual? Do we really love to prick our fingers a zillion times a day?

Every day is different for a person with diabetes, so trends and patterns may not show up on blinded CGM. Even if they do, they are not permanent, because life is not that consistent. Some say unblinded CGM leads to what's called the "Hawthorne effect." That concept suggests that if we see the blood sugar (glucose) result, we will change our behavior based on them. However, this effect is beneficial to people with diabetes. If someone changes their daily habits for the better by seeing his or her blood sugar values in real time day and night, then they may not need a new diabetes medication or insulin dose adjustment.

In my opinion, there is no role for blinded CGM except for formal clinical research studies that must determine the true effect of a medication on a person with diabetes without any other influences. Real-time unblinded CGM is the standard of care for type 1 diabetes right now. It is predicted to become a valuable asset for people with type 2 diabetes, as well.

Continue Learning about Diabetes


Diabetes mellitus (MEL-ih-tus), often referred to as diabetes, is characterized by high blood glucose (sugar) levels that result from the body’s inability to produce enough insulin and/or effectively utilize the insulin. Diabetes ...

is a serious, life-long condition and the sixth leading cause of death in the United States. Diabetes is a disorder of metabolism (the body's way of digesting food and converting it into energy). There are three forms of diabetes. Type 1 diabetes is an autoimmune disease that accounts for five- to 10-percent of all diagnosed cases of diabetes. Type 2 diabetes may account for 90- to 95-percent of all diagnosed cases. The third type of diabetes occurs in pregnancy and is referred to as gestational diabetes. Left untreated, gestational diabetes can cause health issues for pregnant women and their babies. People with diabetes can take preventive steps to control this disease and decrease the risk of further complications.

Important: This content reflects information from various individuals and organizations and may offer alternative or opposing points of view. It should not be used for medical advice, diagnosis or treatment. As always, you should consult with your healthcare provider about your specific health needs.