CGMs vs Finger Sticks in Blood Glucose Monitoring – Which is More Accurate?

    cgms vs finger sticks

    The importance of blood glucose monitoring for diabetics cannot be overstated. As the prevalence of diabetes continues to rise globally, with an estimated 537 million adults living with diabetes in 2021, regular monitoring of blood glucose levels has become a crucial aspect of managing this chronic condition. It helps in identifying patterns of blood glucose level fluctuations, which can occur in response to diet, physical activity, medication, and stress. 

    Two of the most popular methods to measure glucose levels are Continuous Glucose Monitors (CGMs) and finger stick glucometers. However, a question often arises – which of these devices is more accurate in monitoring blood glucose? This blog aims to delve into this topic and shed light on the accuracy of CGMs and finger sticks.

    Defining CGMs and Finger Sticks

    Continuous Glucose Monitors (CGMs)

    CGMs are innovative devices that track glucose levels in real-time throughout the day and night. They measure glucose in the interstitial fluid – the fluid between the body’s cells. CGMs can provide valuable data about glucose trends, helping individuals with diabetes make informed decisions about food intake, physical activity, and medication.

    Finger Stick Glucometers

    Finger stick glucometers, on the other hand, require a small blood sample, usually obtained by pricking the finger with a lancet. These devices measure the current blood glucose level at the time of testing. While they do not provide continuous monitoring like CGMs, they are widely used due to their affordability and accessibility.

    Finger Stick vs. CGM Accuracy: Which is More Accurate?

    While both CGMs and finger stick glucometers play an essential role in diabetes management, their accuracy varies. No device can guarantee 100% accuracy in blood glucose monitoring due to various factors like calibration, user technique, and physiological differences. However, the Food and Drug Administration (FDA) requires all blood glucose meters to be accurate within about 15-20%.

    CGM: An Overview of Its Accuracy and Advantages

    Continuous Glucose Monitors, or CGMs, offer several advantages over traditional fingerstick glucometers. Firstly, they collect data continuously throughout the day and night, providing detailed insights into glucose trends. This data can help users understand how different factors like food, exercise, stress, and medication affect their glucose levels.

    Moreover, CGMs can alert users when their glucose levels are too high or low, allowing them to take immediate action. This feature is particularly beneficial for people with type 1 diabetes who are at a higher risk of hypoglycemia.

    When it comes to accuracy, CGMs have shown promising results. Studies have found that newer models of CGMs are quite accurate, with a Mean Absolute Relative Difference (MARD) – a measure of accuracy – of less than 10%. However, it’s essential to note that CGMs measure glucose in the interstitial fluid, not the blood, which can lead to a slight lag in readings compared to blood glucose levels.

    Finger Stick Glucometers: An Overview of Its Accuracy and Advantages

    Finger stick glucometers have been the standard method of monitoring blood glucose levels for many years. They are widely accessible, reasonably priced, and simple to use. In contrast to CGMs, fingerstick glucometers measure glucose directly from the blood, providing an accurate snapshot of the blood glucose level at the time of testing.

    In terms of accuracy, fingerstick glucometers are required by the FDA to be within 15% of a lab measurement 95% of the time. However, their accuracy can be affected by various factors, including user technique, the quality of test strips, and environmental conditions.

    Factors Influencing Glucose Level Measurement Accuracy

    Regardless of whether you choose a CGM or a finger stick glucometer, it’s crucial to understand that several factors can influence their accuracy.


    For CGMs, calibration is a critical factor in ensuring accurate readings. Calibration involves using a blood glucose meter to test your blood sugar and then entering the result into the CGM. This process helps the CGM understand how glucose levels in your interstitial fluid relate to your blood glucose levels.

    User Technique

    For finger stick glucometers, user technique plays a significant role in the accuracy of readings. Factors such as not washing hands before testing, using expired or improperly stored test strips, or not applying enough blood can significantly impact the accuracy of the results.

    Physiological Differences

    Individual physiological differences also play a role in the accuracy of these devices. For instance, dehydration and changes in temperature can affect blood glucose readings.

    Balancing Accuracy with Personal Needs

    While accuracy is a crucial factor in choosing a blood glucose monitoring method, it should be balanced with personal needs and lifestyle. For some people, the continuous monitoring and alerts provided by a CGM may outweigh the potential for slight inaccuracies due to lag time. For others, the lower cost and simplicity of a finger stick glucometer may be more appealing.

    Which is Better: CGMs or Finger Sticks?

    In managing diabetes, both Continuous Glucose Monitors (CGMs) and finger stick glucometers prove to be invaluable assets. They each possess unique strengths and limitations that make them suitable for different individuals based on their specific needs, lifestyle, and resources.

    For those who need constant monitoring and a comprehensive understanding of the various factors influencing their glucose levels, CGMs often emerge as the superior choice. They provide real-time tracking and deliver critical insights into glucose trends, enabling proactive management of the condition.

    On the other hand, if affordability and occasional blood glucose checks align more with your requirements, finger stick glucometers could be the ideal choice. Despite their lack of continuous monitoring, they are widely accessible and straightforward to use, providing an accurate snapshot of your blood glucose level at the time of testing.

    While both devices exhibit comparable accuracy, it’s vital to note that no tool can guarantee absolute precision due to a host of influencing factors. Consequently, considering these devices’ relative accuracies should be balanced against your personal needs and lifestyle preferences.

    Ultimately, the decision between CGMs and finger stick glucometers is a personal one and should be made in consultation with your healthcare provider. By understanding your unique needs and circumstances, you can choose the method that best empowers you to manage your diabetes effectively.