CGM Interference Profiles Comparison

Introduction to CGM Interference Profiles

Which substances can throw off a continuous glucose monitor (CGM) depends mostly on how its sensor turns glucose into a signal. Dexcom, Abbott and MiniMed sensors are electrochemical. In the Dexcom G7 and FreeStyle Libre sensors, an enzyme called glucose oxidase reacts with glucose and the sensor measures the resulting electric current [7][10]. The Eversense 365 from Senseonics is optical, so it reads light from a glucose-binding indicator instead [4]. When we lined up the interference warnings in the current FDA review documents, the two groups shared nothing: the drugs named for the Dexcom G7 and MiniMed Simplera don't appear in the Eversense 365 warnings, and the reverse holds too [1][3][4]. This page compares those profiles as of October 2026.

Electrochemical CGM Systems

Electrochemical sensors can be fooled by substances that react at the working electrode, which is the part of the sensor that collects the current. The extra current looks like extra glucose, so the reading comes out falsely high (false hyperglycemia) [1][3][6]. The main interferents named in current labeling are:

• Acetaminophen: Dexcom designed the G6 sensor to reduce the acetaminophen interference seen in its earlier G4 and G5 systems, where the drug had been contraindicated [9]. The G6 is being phased out: Dexcom says it will no longer manufacture the G6 after July 1, 2026, though pharmacies may still have supplies for a while [8]. Its replacements, the Dexcom G7 and G7 15 Day, carry the same limit in their labeling. Readings stay usable with a standard dose (up to 1 gram every 6 hours in adults) and run falsely high above it [1][7]. MiniMed's Simplera labeling names no safe amount. It says any medicine containing acetaminophen can falsely raise readings, with an error that depends on how much is active in the body [3].
• Ascorbic Acid (Vitamin C): The often-quoted 500 mg per day threshold belonged to the original FreeStyle Libre 2. Abbott redesigned the sensor tail to reduce vitamin C interference, and the labeling for the redesigned sensor says that taking more than 1000 mg of vitamin C per day may falsely raise readings [2]. Here's what surprised us: in the 60-person study behind that change, the largest average bias after a single 1000 mg dose was 5.1 mg/dL [2]. The FDA's clearance of the current Libre 2 Plus and Libre 3 Plus sensors points back to that same interference work [10]. As of October 2026 the Plus sensors are Abbott's current ones, since the non-Plus Libre 2 and Libre 3 sensors were available only through September 30, 2025 [11].
• Hydroxyurea: This drug, used for some cancers and for sickle cell anemia, makes Dexcom G7 and MiniMed Simplera readings falsely high [1][3]. In the FDA documents we read, it appears in the interference and warning sections rather than as a listed contraindication. Dexcom's labeling says not to use the G7 for treatment decisions while taking hydroxyurea [1]. The Simplera labeling goes further, saying not to use CGM at all, because readings can run substantially higher than blood glucose [3]. The FDA approved Simplera in July 2024 as a supplement to the 2018 approval of the Guardian Connect, which MiniMed has since superseded [3]. If you take hydroxyurea, how to check your glucose is a decision for your care team.

Optical CGM Systems (Eversense)

The Eversense 365 has no enzyme and no electrode reaction. A fluorescent indicator grafted onto the implanted sensor binds glucose reversibly, and binding makes the indicator glow more brightly; the sensor's optics measure that change [4]. So "fluorescence quenching" doesn't describe how it senses glucose. Quenching is part of the resting chemistry: glucose binding at the indicator's boronic acid groups switches off an internal quenching effect, which is why the light gets brighter as glucose rises [5]. We explain the sensor itself in Implantable Fluorescence Sensors (Eversense).

That design changes the interference picture. Senseonics scientists tested 41 substances in the lab against the original Eversense sensor, and neither acetaminophen nor vitamin C produced bias beyond ISO 15197:2013 limits at physiologic concentrations [5]. That is an in vitro result from the manufacturer's own employees, not proof of immunity. Two drug groups did interfere at therapeutic concentrations, and the Eversense 365 labeling still warns about both [4][5]:

• Tetracyclines: Tetracycline-class antibiotics, including doxycycline and minocycline, may falsely lower readings, and the labeling says not to rely on sensor readings while taking them [4]. The Senseonics team chose tetracycline for testing because it absorbs or fluoresces light at wavelengths that overlap the sensor's indicator [5].
• Mannitol: Mannitol or sorbitol given intravenously, or as part of an irrigation or peritoneal dialysis solution, can falsely raise readings. The labeling adds that sorbitol from a typical diet doesn't affect them [4]. The Senseonics paper notes that substances able to bind the indicator polymer can interfere, but we didn't find it naming binding as the specific cause for mannitol [5].

Oxygen Interference

Oxygen levels can also interfere with CGM readings. Dexcom's G6 review describes the basic chemistry of its sensor: glucose oxidase oxidizes glucose and produces hydrogen peroxide, and the peroxide generates a current proportional to glucose [9]. Abbott's FreeStyle Libre sensors use what Abbott calls Wired Enzyme technology. The enzyme hands its electrons to an osmium-complex mediator, which shuttles them to the electrode at only 40 mV, and two Abbott engineers write that this low potential keeps other substances from oxidizing there [6]. This design allows Abbott's sensors to function independently of tissue oxygen levels. In contrast, Dexcom and Medtronic sensors rely on glucose-limiting membranes to manage the oxygen-to-glucose ratio.

Conclusion

No CGM in this comparison is free of interferents; the list changes with the chemistry. For the Dexcom G7, the labeled concerns are acetaminophen above a standard dose and hydroxyurea [1]. For the current Libre 2 Plus and 3 Plus, the labeling points to vitamin C above 1000 mg a day [2][10]. The Eversense 365 trades those for tetracyclines and for mannitol or sorbitol given in a clinical setting [4]. The FDA summaries we cite quote only parts of each label, so the full user guide for your sensor holds the complete list. If you take any of these medicines, whether your CGM readings can guide treatment is a question for your care team.