What is a CGM? Continuous Glucose Monitors explained.

What is a CGM? A Continuous Glucose Monitor can help you test your blood sugar with ease, and manage your diabetes better. Here’s all you need to know to make an informed decision.

What is a CGM? Continuous Glucose Monitoring

A CGM is a Continuous Glucose Monitor: a sensor that is inserted into your body (usually your stomach, upper arm or thigh) that takes constant blood sugar readings throughout the day. When the sensor is inserted, there’s a needle to open the skin, and then a tiny filament is left behind. This filament takes glucose readings in the interstitial fluid (the fluid surrounding the cells) all day and night: 24 hours a day. 

These readings are sent to a reader, usually an app on your smartphone. This means you can see what your blood sugar is doing every hour of the day. Most CGMs also come with high and low alerts, so they will sound an alarm if your blood sugar is above or below your target range. Because the readings are coming from the interstitial fluid and not the blood, they are generally around 10 minutes ‘behind’ a fingerstick blood glucose test.

Why is CGM so helpful for people with diabetes?

CGM is enormously helpful. Life-changing, even. Instead of just 4 or 5 readings at points during the day, you get to see a wealth of data to understand your diabetes. You can see at a glance what your blood sugar is doing now, and where it’s going. Trend arrows are probably the most powerful part of this tech, as they tell you not only what your blood sugar is doing right now, but if it’s going up or down. And if it’s going up or down, is it a gradual increase or decrease, or an urgent one? It is much easier to avoid high highs and low lows with this information.

How do you read CGM trends and reports?

The other kind of data available to you is trend graphs (so you can see if you tend to go high or low at a certain time of day), time in target percentage (so you know how much of every day you’re spending in your target range) and average blood glucose. Because all the data is online, it’s also much easier to share with your doctor remotely.

Of course, there are plenty of long-term benefits to using a CGM too. Numerous studies have shown that this diabetes tech can improve HbA1c, reduce time spent in hypoglycemia (low blood sugar) and increase time spent in a normal blood sugar range. Read the studies here, here and here.

You can also easily track your insulin doses, carbs and exercise so it acts as a diet diary and a reminder of what time you took your insulin. This is invaluable because it can let you know if you need to wait a while before giving a correction dose (if you’re going high) or whether you need to react immediately. 

How do you decide what’s right for you?

If you are ready to take control of your diabetes, a CGM can be life-changing. The information it offers is a full picture of how your blood sugar behaves all day and night. This can empower you to make the right decisions regarding food and exercise. It also helps to discuss your diabetes treatment plan with your doctor, decide if you need to change your insulin dosage, and help you spend more of your time in your target range.

The choice of which CGM is right for you is a personal one – and one that you need to discuss with your doctor.

Factors to consider include:

Reliability: the number 1 thing to consider! Make sure the CGM you are considering passes the CGM Accuracy Checklist.

• Price.
• Size.
• Type of alarms available (not all CGMs offer a ‘low soon’ or ‘urgent low soon’ alarm, which can help prevent low blood sugar before it happens.)
• Whether or not it needs to be calibrated: some people don’t want to do any fingerstick blood tests, so they prefer the option of a CGM that doesn’t need to be calibrated.
• What the app experience is like (all CGMs connect to an app, and the apps have different functionality and appearance).
• Customer support.
• Connection to smart insulin pens.

You can always test out the various systems and discuss what works for you with your doctor.

How do you get a CGM?

Many medical aids offer CGM Benefits for people with Type 1 diabetes. Here’s how to motivate for your medical aid to cover a CGM.

SA Diabetes Advocacy is working hard to advocate for CGMs in public care.

If your medical aid rejects your request for a CGM you can complain to the CMS. Here’s exactly how to do that.

Any more questions about CGMs?

We hope this has answered all your questions about how CGMs work. If you still have questions, ask us below and we’ll find the answers!