What if you have a continuous glucose monitor (CGM)?

People with diabetes, particularly those with type 1 diabetes, may also choose to use CGMs. These devices measure your blood sugar every few minutes using a sensor inserted under the skin. These sensors are typically worn for a week or two before they need to be changed.

The newest type of continuous glucose monitor has an implanted sensor that can detect blood sugar levels for up to three months. A transmitter worn on the body sends blood sugar information wirelessly from the sensor to a smartphone app.

Some devices show your blood sugar reading at all times on a receiver, smartphone or smartwatch, and an alarm goes off if your blood sugar is going up or down too quickly. Others require that you check your blood sugar by running the receiver over the sensor periodically.

Most of these devices still require finger-stick checks to calibrate the machine. Check your device's users guide to learn if you need to check, and if so, how often you need to do it.

Certain medications, such as acetaminophen (Tylenol, others), albuterol (Proair HFA, Ventolin HFA, others) and lisinopril (Prinivil, Zestril, Qbrelis), may interfere with the accuracy of some CGM readings, particularly on older models of CGMs. Readings on newer CGMs don't seem to be affected by standard doses of acetaminophen (up to 1,000 milligrams for an adult).

If you need to take medications that may affect the accuracy of the readings, your doctor may recommend double-checking your CGM results with a standard blood sugar meter. Check with your doctor about using a CGM if you're pregnant, on dialysis or critically ill, as these conditions may affect the blood sugar readings from a CGM.