False Glucose Readings: What Are They and What Causes Them?

Fluctuations in blood sugar are normal, and if you’re metabolically healthy, your body is fully capable of bringing your blood sugar back to normal. Sometimes, the foods you eat, a stressful event, or an intense workout can cause a spike in your blood glucose. But if you notice significant changes in your readings and cannot identify the cause, you might have experienced a false reading, which can have several causes. 

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What Causes False Readings?

Medications and Supplements

Some medications and supplements may cause changes in your blood glucose readings even if your blood sugar hasn’t actually changed. Acetaminophen (commonly known as Tylenol) is a widely used pain reliever and fever reducer, but it can also cause falsely high readings. Lisinopril, a prescription medication used to treat high blood pressure, and albuterol, used to treat asthma, have also been shown to interfere with CGM readings.¹ 

If you take any of these medications, you may want to speak with your medical provider about other options. 

Taking a Vitamin C supplement may also cause falsely elevated readings due to electrochemical interference. To alleviate this interference, aim to get your dose of this potent antioxidant from whole food sources such as citrus fruits, strawberries, broccoli, kale, and brussels sprouts.² 

Sensor Issues

An important part of ensuring accurate blood glucose readings with a CGM is making sure that your sensor is properly placed and functioning. After you install a new sensor, it takes about 48 hours for it to calibrate. If you notice abnormal highs and lows during this time, don’t worry; these readings are probably not accurate. 

Your sensor should be placed in an area that is optimal for reading. If you place it over scar tissue, muscle, or bone, it may not be able to measure interstitial fluid glucose levels accurately. Additionally, if the sensor isn’t properly attached to the skin, you may get false readings. 

Pay attention to how often you replace your sensor. The Signos CGM sensor is designed to last 10 days. Ensure you promptly replace it and don’t use it past its expiration date, as doing so may cause false glucose readings. 

Another common sensor issue while you sleep is pressure on the part of your body where the sensor is attached, such as your arm. This pressure can interfere with blood flow to the area, causing a faulty reading. These readings are often falsely low, so much so that your CGM might alert you that your blood glucose is dangerously low, even though it actually isn’t. 

The best way to avoid these late-night false readings is to place your sensor on an area of your body that you don’t sleep on. 

Dehydration

You probably already know that staying hydrated is important for overall health and well-being and for accurate CGM readings. If you’re dehydrated, the volume of interstitial fluid in your body is reduced, which can affect the glucose concentration in the interstitial fluid, potentially causing false readings. Dehydration can also delay the detection of glucose changes and negatively impact the sensor’s ability to measure glucose. 

Drink plenty of water throughout the day to prevent false readings caused by dehydration. Cross-check your CGM data with a glucometer if you suspect that your glucose readings are inaccurate due to dehydration. 

Temperature Extremes 

Extreme temperatures can affect the way your sensor measures interstitial glucose. The recommended operating temperature for a CGM is between 50 and 113 degrees Fahrenheit, so you may get inaccurate high or low readings if you wear your CGM in temperatures outside of this range, like in a sauna, ice bath, or hot tub. 

<div class="pro-tip"><strong>Also Read: </strong><a href=cgm-vs-fingerstick-glucometers>Cgm vs Finger Sticks: Most Accurate Glucose Meter</a></a>.</div>

How to Prevent False Glucose Readings

While some false readings are inevitable, there are some things you can do to help ensure your CGM readings are accurate:

• Place the sensor as recommended by the manufacturer. The abdomen and the back of the upper arm tend to be the best places. If you place it on your arm, remember to choose the one you tend not to sleep on. Avoid placing the sensor over muscle or scar tissue.
• Follow all sensor adhesion directions. Clean the site thoroughly with alcohol and allow it to dry completely before placing the sensor. Use adhesive patches or tape to keep the sensor properly in place and avoid movement that may cause erroneous readings. 
• Stay adequately hydrated. Aim to drink at least 64 oz of water per day. 
• Avoid taking medications or supplements that may interfere with the sensor’s ability to accurately read interstitial glucose. If you’re not sure whether your current medication and supplement regimen are interfering with your CGM, talk to your doctor.
• Avoid extreme temperatures like in a cold plunge, sauna, or hot tub.
• Replace your Signos CGM sensor as recommended every 10 days. 
• Keep your CGM and phone app software up-to-date. 

Learn More About the Signos CGM Program

Signos incorporates cutting-edge research and the proven power of continuous glucose monitoring. The data gleaned from the Signos app can help guide your health journey. Not sure if Signos is right for you? Take this quiz to find out! Interested in learning more about nutrition and healthy eating habits? Check out more articles on our blog.

<div class="pro-tip"><strong>Learn More: </strong><a href=cgm-guide>A Comprehensive Guide to Continuous Glucose Monitors</a>.</div>