By Athena Philis-Tsimikas, M.D., Scripps Health
For many of the 26 million adults and children in the U.S. with diabetes, testing blood sugar levels is as much a part of their daily routine as brushing their teeth. Self-testing enables people with diabetes to monitor the amount of glucose in their blood at various times during the day, determine whether levels are acceptable, and make the necessary adjustments to their diet, activity or medications if they are not.
Glucose self-testing is done by pricking a finger and placing a small drop of blood on a special test strip. The strip is then read by a portable electronic device called a meter, which measures the amount of glucose in the blood.
How often people need to self-test depends on the type of diabetes as well as other factors. Generally, people with type 1 diabetes test three or more times a day, including before and after meals. People with type 2 diabetes may test anywhere from every few days to multiple times a day depending on whether they use insulin, take medications, or have other health conditions.
While the finger-sick test is highly effective for providing “snapshots” of blood sugar levels at a given time, it cannot provide information about glucose trends over several hours or days. For example, it has no way of showing if a person’s blood sugar drops to dangerously low levels while they are asleep at night, or regularly spikes between meals. Such fluctuations and trends provide important information that can influence the treatment plan, but because it isn’t captured by the finger-stick test, the patient and health care providers are unaware of it.
Continuous glucose monitoring systems address this need by tracking glucose levels several times a minute around the clock while the patient goes about his or her usual day-to-day activities. A tiny device that senses glucose levels is implanted just under the skin of the abdomen. The sensor measures the blood sugar levels every 10 seconds or so and wirelessly transmits the information to a pager-sized monitoring device worn on the clothing, which keeps a record of the readings. Some devices provide nearly 300 measurements in a 24-hour period.
Continuous glucose monitoring does not replace the finger-stick test; instead, it is used in conjunction with it to more accurately monitor glucose levels. Patients who use the continuous system must also perform finger-stick tests as often as recommended by their physician, and the results are recorded and checked against the system’s numbers for calibration. In addition, patients keep a record of everything they eat and drink, physical activities, and medications, to identify how these affect glucose levels.
In some cases, monitors may include alarms that alert patients when their blood sugar levels are too high (hyperglycemia) or too low (hypoglycemia), so that patients can take action to get their levels back to normal. Again, a finger-stick test is usually recommended to verify the results before adjustments are made. This can be especially helpful if patients do not have any symptoms or warning signs that their blood sugar is too high or low.