Medications That Impact CGM Accuracy — and Why It Matters

Continuous glucose monitors (CGMs) have revolutionized diabetes management. These wearable devices measure interstitial glucose levels every few minutes, offering alerts for rising or falling trends in real time. But while CGMs have made glucose tracking more convenient and insightful, their accuracy can be affected by certain medications and supplements.

When readings are skewed, users may make incorrect insulin or dietary decisions—potentially leading to hypoglycemia or hyperglycemia. Understanding which medications can interfere with CGM sensors helps ensure safer, more effective diabetes care.

Why Medications Can Interfere With CGM Readings

CGMs rely on electrochemical sensors that measure glucose in interstitial fluid rather than directly in the blood. Some medications contain electroactive compounds or cause metabolic changes that can interfere with how the sensor detects glucose levels. The result may be false highs or false lows, depending on the specific drug and device technology.

Common Medications and Substances That Interfere With CGMs

1. Acetaminophen (Tylenol)

• Impact: Can cause falsely high glucose readings on some sensors.

• Reason: Acetaminophen is electrochemically active and alters the current used by glucose oxidase sensors.

• Device Sensitivity:

  • Dexcom G4 and G5 users reported false highs at doses >1,000 mg.

  • Dexcom G6 and G7 have integrated filters that significantly reduce interference at normal doses.

  • FreeStyle Libre systems may still be affected by higher acetaminophen doses.

• Tip: Confirm unexpected results with a finger-stick.

2. High-Dose Vitamin C (Ascorbic Acid)

• Impact: Can lead to falsely high glucose readings.

• Reason: Vitamin C donates electrons that alter the electrochemical signal.

• Device Sensitivity:

  • FreeStyle Libre 2 and 3 warn that vitamin C > 500 mg/day may overestimate glucose levels.

  • Dexcom G6/G7 are less affected but still recommend meter confirmation with high doses.

3. Aspirin / Salicylates

• Impact: May cause falsely low glucose readings.

• Reason: Salicylates inhibit hepatic glucose production and may also interfere with glucose oxidase reactions.

• Device Sensitivity:

  • Minimal with modern Dexcom and Abbott sensors; effects were greater in early models.

4. Hydroxyurea

• Impact: Causes falsely high readings across several CGM brands.

• Reason: Hydroxyurea’s electroactive properties directly interfere with the sensor’s electrodes.

• Device Sensitivity:

  • Documented interference with Dexcom G6 and G7.

  • FreeStyle Libre may also be affected by a similar mechanism.

5. Other Medications (Lisinopril, Atenolol, Albuterol)

• Impact: May indirectly alter readings by affecting blood flow or glucose metabolism.

• Reason: These changes are physiologic rather than electrochemical.

• Device Sensitivity:

  • Applies across brands; usually mild and transient.

Are All CGMs Affected Equally?

No — different technologies vary in susceptibility:

What Users Can Do

1. Keep an up-to-date list of all prescriptions, OTC medications, and supplements.

2. Cross-check unusual readings with a finger-stick if symptoms don’t match CGM data.

3. Review manufacturer guidance for your specific sensor model.

4. Inform your healthcare provider before starting new medications or supplements.

5. Track patterns — note when you take certain drugs and whether readings trend differently.

CGMs are powerful tools that empower people with diabetes to make timely, informed decisions. However, their readings can be distorted by medications or supplements that alter electrochemical reactions.

By understanding which substances interfere and which technologies are most resilient, users can interpret their CGM data more accurately and avoid unnecessary treatment errors. Awareness, communication, and periodic finger-stick confirmation remain the best safeguards for staying in control.

You may also be intereted in reading Doctor with Diabetes Breaks Down How BGM and CGM Work Differently.

Source:

Diabetes Sci Technol.

Diabetes Care

Dexcom 

Abbott FreeStyle Libre 

Ascensia Diabetes Care/ Eversense 

The post Medications That Impact CGM Accuracy — and Why It Matters appeared first on Diabetes Health.