Does Drinking Alcohol Throw Off Your CGM Readings?

What Was Studied and Why It Matters

Continuous glucose monitors (CGMs) have become one of the most important tools for people living with Type 1 diabetes (T1D). They provide real-time glucose readings that help guide insulin decisions around the clock. But what happens to those readings when you have a drink with dinner?

Researchers in Spain set out to answer exactly that question. They looked at whether drinking beer alongside a mixed meal could interfere with the accuracy of a popular type of CGM sensor — one that uses an enzyme called glucose oxidase (GOx) to measure blood sugar. These GOx-based sensors are the most widely used CGMs on the market today.

How the Study Worked

Twelve adults with Type 1 diabetes participated in a carefully designed crossover trial, meaning each person completed both an alcohol and a non-alcohol version of the test. In one session, participants ate a mixed meal with beer. In the other, they ate the same meal without alcohol. Researchers then compared how closely the CGM readings matched actual blood glucose levels in both scenarios.

Two key accuracy measures were used:

• Absolute Error (AE): The raw difference between the CGM reading and the real blood sugar value
• Mean Absolute Relative Difference (MARD): A percentage-based measure of how far off readings were on average

What the Findings Show

The results revealed that alcohol consumption did meaningfully affect CGM accuracy. Specifically:

• The absolute error was significantly higher during the alcohol session compared to the non-alcohol session
• The MARD was also higher with alcohol, though this difference did not reach statistical significance
• Both accuracy measures were worse when the body's pH dropped below 7.36 — a slight but meaningful shift toward acidity that alcohol can trigger
• Sensor readings drifted more over time during the alcohol session, suggesting the interference builds as alcohol is processed

The researchers believe that alcohol may alter the chemistry around the sensor just under the skin, partly by nudging the body's pH in a direction that disrupts how the glucose oxidase enzyme functions.

What This Means for Real Patients

If you wear a CGM and occasionally drink alcohol, this study is a useful reminder to treat your sensor readings with a bit more caution in those situations. A CGM reading that looks stable after a beer or two may not be telling the full story — especially in the hours after drinking.

Practical steps to consider:

• Use a fingerstick blood glucose check to confirm CGM readings before making insulin adjustments after drinking
• Be especially cautious about low glucose alarms, which could be masked or delayed
• Talk to your diabetes care team about your specific CGM model and how alcohol fits into your management plan

Having reliable supplies on hand — including backup fingerstick test strips and lancets — is always a smart idea. MDS Diabetes carries a full range of glucose monitoring supplies to help you stay prepared in any situation.

Bottom Line

Drinking alcohol with a meal can reduce the accuracy of glucose oxidase-based CGM sensors in people with Type 1 diabetes. The effect appears linked to small shifts in body pH caused by alcohol. Until more research clarifies the full picture, it is wise to double-check your CGM readings with a traditional fingerstick test when drinking, and to let your healthcare provider know if you notice unusual sensor behavior after alcohol consumption.