Time is a new metric for people with diabetes, and 75 years ago, it would have no meaning for people with the disease. Because they rarely knew what their blood sugar levels were at some point.
In the 1940s, measuring blood glucose – essential knowledge for people with diabetes – was a labor and indirect process. People had to add eight drops of urine to a teaspoon of Benedict’s solution, boil the mixture for at least five minutes, and compare the color to a graph. It’s not the kind of thing that can be easily done, and it’s not very accurate. By the 1960s, it was possible to urinate in a test strip to obtain blood sugar indirectly. The test strips of blood glucose were measured. Checking for such fingerprints may not take much time, but it is not advisable for driving, business meetings, eating, exercising, or sleeping.
These tests only show glucose levels at the fingertips, and they take only a small amount of blood sugar per day. In the 1980s, a different blood test, known as hemoglobin A1C (HBA1C), assessed a person’s average blood sugar level within three months. In people without diabetes, HbA1c readings are below 5.7%. This test helps people with diabetes and their doctors to tell you if a treatment plan is in place, but not perfect.
A major breakthrough in blood sugar testing came from the development of commercial glucose monitors (often referred to as GCMS) introduced commercially in 1999. Finger sticks and HBA1C, I think, are more informative films.
The CGM is equipped with a very small sensor inserted below the skin. It painlessly monitors the glucose level in the intermediate spaces between cells.
The sensor sends wirelessly every few minutes to a small, portable receiver or compatible smartphone or tablet. Alarms and warnings indicate glucose levels are above or below the user-set limits, and blood sugar levels can be adjusted for rapid rise or fall.
The CGM provides a subtle look at the blood sugar level around the clock. Users can see how different diets and exercises affect their blood sugar. They can correct reading of a calibrated dose of insulin or a handful of raisins or juice.
With nearly 300 blood sugar measurements per day, CGM offers a new way of assessing how a person manages their diabetes.
Recently approved by the American Diabetes Association and an International Convention Committee, this metric is closely associated with diabetes management and the development of complications such as loss of vision, kidney problems, and low blood sugar excursions. Most of the time in the range is associated with more stable glucose control, which should result in fewer complications.
Since most of my patients use continuous glucose monitors, I find that I am less dependent on HbA1c and more on timing. CGM does not know how long a patient spends with low blood sugar, when they are sleeping, and how much time they spend with high blood sugar. Looking at company data makes it easier to identify weekend activity, women’s pre-menstrual patterns, changes in employment, sick days, and other patterns.
Like all new metrics, it will take patients and doctors time to utilize it fully. With the advent of the artificial pancreas, I believe this will soon be the standard for a strict insulin regime and game changer – a closed-loop system that connects a CGM to an insulin pump.