Blood Glucose Meter and Continuous Glucose Monitor: What’s The Difference?

Blood Glucose Meter and CGM: What’s The Difference?

If you have been diagnosed with diabetes, you may need to monitor your blood glucose levels several times daily to reduce the chance of complications [1]. You can do so in one of two ways: with a blood glucose meter (also known as a blood glucose monitor) or a continuous glucose monitor (CGM).

How do these therapeutic tools work, and which one should you choose? In this article, we compare the blood glucose meter with the CGM so that you can pick the one that is right for you.

What is a blood glucose meter?

A blood glucose meter is a device that helps you measure the glucose levels in your blood [2, 3]. Glucose levels can change due to many factors, such as  exercise, dietary choices, or medications [2]. 

When you live with diabetes, understanding how your blood glucose fluctuates and how activities or foods affect it can help you and your healthcare practitioner develop the most appropriate treatment plan. 

A blood glucose monitor can help you identify t if your blood glucose is too high, too low, or within range. This way, you can aim to prevent or treat  episodes of hyper- or hypoglycaemia and reduce the risk of serious complications from diabetes [4]. 

Blood glucose meters need a tiny blood sample to detect glucose — usually, this is a blood drop taken from your fingertip [3, 4].

How does a blood glucose meter work?

A blood glucose meter analyses a small droplet of blood from a test strip. [5].

A small needle, called a lancet, is used to prick the finger and collect the small droplet of blood [2]. Then, the droplet is placed on the testing strip and inserted into the blood glucose meter. Inside the blood glucose meter is an interface to an electrode, which is used to obtain a blood glucose reading [5]. The reading is then displayed on a screen in units of mmol/L [4].

When the strip goes inside the blood glucose meter, the glucose reacts with the glucose oxidase enzyme on the strip and generates an electrical signal. The higher the electrical current, the higher the glucose detected and the number appearing on the blood glucose meter’s screen [5].

Blood glucose meter: how to use

All blood glucose meters are slightly different, so following your user’s manual instructions is important. 

However, generally, to use a blood glucose meter, you will mainly need [1, 4]:

• A blood glucose meter
• Testing strips
• A lancet
• Soap and water 

You should consult with your healthcare practitioner on the best time of the day to monitor, as well as the frequency of monitoring [1]. Also, although most blood glucose meters work by pricking the finger, some allow the blood sample to be taken from your upper arm or thigh. Check the blood glucose meter’s manual for instructions on alternative  testing sites [1, 4].

Using a blood glucose meter: step by step 

To take the test, follow these steps [1, 2, 4]: 

1. Wash your hands thoroughly with soap and water. This is to prevent infection. Ensure your hands are dry before taking the test [1, 4].

2. Make sure the testing strip is not outdated [1]. Insert the strip inside the blood glucose meter. This often turns on the blood glucose meter [2]. 

3. Use the single-use lancet to draw blood from the side of your finger. To ensure blood will come out, warm your hands first by rubbing them together or placing them under warm running water [4]. To get the blood droplet, apply the lancet on the side of the finger firmly but not with force [1]. Create a gentle ‘milking’ motion from the finger's base to the lancing site [1].

4. Place the blood on the testing strip according to the instructions. Some strips directly absorb a small droplet from the testing site, others need the droplet to be over the entire testing pad [4].

5. Finger-pricking rarely causes more than a couple of drops of blood, You may need to apply pressure on the testing site to avoid further bleeding [2].

6. Note the blood glucose value on the blood glucose meter screen and record it. Modern, ‘smart’ blood glucose meters sync readings with mobile or desktop apps via Bluetooth [2], while others will require you to keep track manually in a notebook or a blood glucose diary.

Your diabetes healthcare team will also be able to walk you through using a blood glucose meter.

What is the difference between a CGM and a blood glucose meter?

Continuous glucose monitoring (CGM) systems became commercially available in 2000 as an alternative to finger-prick testing [6]. Unlike a blood glucose meter, a CGM does not require a blood sample and is less invasive [6].

What is a CGM, and how does it work?

There are several models of CGMs available. 

Generally speaking, a CGM consists of a monitor worn on the body with a thin hair-like sensor placed under the skin [7, 8, 9]. This sensor obtains glucose readings from a person’s interstitial fluid [7, 9], which is the fluid that fills the space between the cells and provides the body with nutrients.

The readings are scanned manually or transmitted via Bluetooth to a receiver that displays and records the readings [9].

Continuous glucose monitor vs blood glucose meter 

If you aren’t sure whether a continuous glucose monitor or a blood glucose meter is most appropriate for you, it is a good idea to look at the advantages and disadvantages or discuss this with your diabetes care team. 

Continuous glucose monitors

There are several advantages to using a CGM. Firstly, a CGM can record measurements as often as every five minutes on the hour [2] or 288 readings a day [9]. With a CGM, you can observe changes in your blood glucose levels almost in real-time and receive alerts, which can help you take immediate steps to prevent a hyper- or hypoglycaemic episode [9]. This gives it nearly 24/7 coverage of a person’s blood glucose patterns and an advantage in predicting, preventing or treating episodes [6]. 

A CGM helps you gain insights into what happens while you are sleeping when you are stressed or engaged in other daily activities [9]. It is particularly helpful for people with low blood glucose levels during the night and individuals who are hypo unaware [2, 6]. 

Studies have linked CGM use with better metabolic control, and a longer time spent in the recommended blood glucose range, less hypoglycaemia, lower anxiety and better quality of life [10].

On the other hand, a continuous glucose monitor is more expensive than a blood glucose meter [11]. They are more complex to understand and require training and time for the user to familiarise themselves with the tool [11]. CGMs do require a high level of compliance and interaction to manage blood glucose levels [11].

And importantly, while using a less invasive CGM with a sensor under the skin is still less painful than doing fingerprick tests every day [9], some  models require multiple daily fingersticks for

calibration with self-monitoring of blood glucose (SMBG) [11]. The sensor is always on the body and requires regular replacement every 5-14 days, depending on the model [11].

Blood glucose meters

Likewise, there are advantages to using a blood glucose meter. Blood glucose meters take accurate measures of capillary glucose concentrations [11], providing results after a short testing time [2] using only a small blood sample [2].

Blood glucose meters are also relatively inexpensive [11] compared to CGM [2]. Crucially, they are widely used and familiar [11], and it is easy to learn how to use them [11]. Glucometers have a range of features — modern smart models have Bluetooth capabilities that can synchronise data with smartphone apps [2]

Frequent self-monitoring of blood glucose (SMBG) using blood glucose meters is fundamental to effective diabetes treatment and daily management [10]. More frequent SMBG has been linked to lower HbA1c levels in patients with type one diabetes and insulin-treated patients with types 2 diabetes [11].

As for negatives, a blood glucose meter provides approximately 4–7 measurements a day [9]. This means that a blood glucose meter offers more limited data than CGM; therefore, its clinical effectiveness is also limited [11]. As they only provide information about a single point in time, it is more difficult to identify trends in blood glucose levels [8, 10].

Blood glucose meters are often regarded as uncomfortable [8], cumbersome [8],  inconvenient [11], and painful [11].  Additionally, the quality of the testing strips may vary due to their short expiration date [2,11].