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Medications to Avoid When Wearing a Continuous Glucose Monitor

Medications like aspirin, Tylenol, and vitamin C can potentially impact the accuracy of continuous glucose monitors (CGMs). Here are steps to ensure reliable diabetes management.

While continuous glucose monitors (CGMs) can provide real-time data and alerts to help people with diabetes make informed decisions about their health, certain common medications can interfere with a device’s accuracy and effectiveness. 

That’s because certain prescription and over-the-counter medications cause reactions in the interstitial fluid, the place just underneath the skin’s surface where CGMs measure blood glucose levels. Depending on what model of CGM you’re using, here’s what to watch out for.


Acetaminophen (Tylenol)

High doses of acetaminophen have been observed to affect the accuracy of Dexcom G4 CGM. Acetaminophen can produce a chemical reaction in the interstitial fluid, leading to increased levels of a compound called acetaminophen glucuronide. 

This compound can be mistakenly detected by the CGM sensor as glucose, resulting in false high glucose readings. While the Dexcom G6 has reduced its sensitivity to acetaminophen, taking more than the maximum dose (over 1 gram every six hours in adults) could falsely raise blood glucose readings.


Even though sensitivities to acetaminophen have been reduced, the Dexcom G6 CGM system still shows a problem when used with a drug called hydroxyurea, which is used for cancer treatment and sickle cell anemia. 

Dexcom’s website states that if you’re taking hydroxyurea, your blood sugar readings may be higher than your actual blood glucose. This could be dangerous as it may lead to missed hypoglycemia alerts or errors when analyzing and interpreting your blood sugar patterns for optimal diabetes management. 

Dexcom does not recommend using their CGM system if you are taking hydroxyurea. Fortunately, only a small number of continuous glucose monitor users take medications like hydroxyurea.


Ascorbic acid (vitamin C)

While vitamin C is essential for our health, extremely high doses – such as those found in certain supplements or cold medications like Airborne and Emergen-C – can potentially affect the accuracy of the Freestyle Libre 2. 

High levels of vitamin C can cause an electrochemical interference with the CGM sensor, leading to inaccurate glucose readings. Abbott’s website states that taking over 500 mg of ascorbic acid (vitamin C) per day may alter sensor readings, which could cause you to miss a severe low blood sugar event. 

Salicylates (aspirin)

Drugs that contain salicylates – like aspirin – have been associated with potential CGM interference of the FreeStyle Libre 14 day flash glucose monitoring system. 

While the exact mechanism is not fully understood, salicylates may influence the chemical composition of the interstitial fluid, affecting the sensor's ability to accurately measure glucose levels. Abbott reports that taking aspirin while using that model of CGM could result in lower glucose readings.

Steps you can take to avoid CGM interference

It's important to note that not everyone will experience interference with their CGMs while taking these or other medications. 

The degree of interference can vary from person to person and from device to device. Some CGM devices may not be affected at all. Nevertheless, it is advisable to be aware of any potential interactions with the CGM you are using and take any necessary precautions to ensure accurate glucose monitoring. 

We recommend carefully reading your device’s safety labels and speaking with your healthcare provider if you have questions about your CGM. If you are taking any of the medications mentioned, consider double-checking with a fingerstick glucose meter or discussing alternatives with your healthcare provider.

To learn more about CGMs, read our other articles: