Dr Paula Diab shares the multiple benefits of continuous glucose monitoring (CGM), highlighting that most people on the diabetic spectrum will benefit from it.

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Around about 10 years I attended an international congress on diabetes. To break the monotony of clinical presentations, the organisers had set up a series of debates entitled just this: “Who needs CGM?”

The debate set-up was listed as follows:

• Children with Type 1 diabetes vs adults with Type 2 diabetes on insulin.
• Adults on Type 2 diabetes on insulin vs adults with Type 2 diabetes NOT on insulin (oral medication only).
• Adults with Type 2 diabetes on oral medication vs adults with pre-diabetes.

At first glance, I thought, naively, that this was going to be a complete waste of time. Why on earth would you want to know what your glucose levels were every 10 minutes of the day if you weren’t even taking insulin? What possible benefit could there be for people without diabetes and not on any medication to monitor themselves so regularly?

I was considering skipping the session and having an early lunch until a colleague dragged me in to stay. Ever since then, I have been a complete convert to CGM and it has revolutionised my practice entirely.

CGM usage has advanced tremendously within the decade it has been available and has become simpler to use, more accessible, more accurate, and the devices have many more functions. It does come at a cost which many funders do not cover but it can also be used intermittently with specific goals in mind to reduce the financial burden.

What is CGM?

A CGM device consists of a small sensor placed under the skin that measures glucose levels in the fluid between cells. It tracks glucose trends throughout the day and night, alerting users to any significant highs (hyperglycaemia) or lows (hypoglycaemia). The device sends data to a smartphone or receiver, allowing for real-time adjustments to food, activity, and medication.

Currently on the South African market there are multiple devices available, some of which link to insulin pumps and others that can be used as a stand-alone option. Application time varies from 10 – 14 days and some require a separate transmitter whilst others have a sensor and transmitter combined. It’s important to ensure you are comparing like devices when assessing costs and evaluating which device is best for your needs.

CGM vs finger pricking

I always compare the use of a CGM to watching a movie when talking with my patients. Imagine your favourite movie as only three or five still images throughout the story. It would be up to you to make up the story in between. This is exactly what happens when we do a few finger pricks during the day and try to make up the story in between.

If you test your glucose level and get a reading of 7.4 mmol/L before a meal, what does this mean? Have you been 7.4 all day long? Were you high after your last meal and then went to exercise resulting in a drop to 7.4mmol/L? Or did you drop low during the exercise and the chocolate milk that you had afterwards pick you up to 7.4mmol/L. It becomes a guessing game unless you have the ability to watch the whole movie and see the trend throughout the day.

Figure 1 below shows two fictitious patients and their glucose levels throughout the day. Patient 1 has very stable readings throughout the day whereas patient 2 seems to fluctuate throughout the day. Both patients begin the day on the same value and both have the same average which indicates the futility of a single-fasting reading every day as well as an average, such as an HbA1c test.

Figure 1: Fictional representation of glucose levels throughout the day.

Night time is another key problem in diabetes management. How often do patients say that they never have a low only to find out they spend most of the early hours of the morning hovering around 3mmol/L and then due to the natural cortisol release that occurs just before we wake up, that level picks up to around 5mmol/L on waking. No one wants to test their glucose levels throughout the night so a CGM can provide valuable information in this regard.

Who benefits from CGM?

1. Type 1 diabetes patients (children or adults)

For anyone with Type 1 diabetes, managing blood glucose can be challenging. The body’s inability to produce insulin means frequent blood glucose checks, and insulin adjustments are critical.

CGM allows you to track your glucose levels continuously without needing finger-sticks throughout the day. It helps predict hypoglycaemia before it happens, potentially preventing dangerous episodes, especially during the night.

2. Remote monitoring

CGM can also be extremely valuable for monitoring children whilst they are at school, away on outdoor excursions, playing sports, etc. All CGM systems have remote following capabilities which means that parents and caregivers can follow their child’s levels throughout the day.

Remote monitoring also becomes extremely useful for patients who are hospitalised, in a care facility, or with reduced independence so that family members, caregivers and healthcare professionals are able to continue to monitor glucose levels without disturbing the patient or relying on irregular finger pricks for information. Various alarms and alerts can be set for each member following, depending on their level of intervention.

3. Type 2 diabetes on intensive insulin therapy

Many people with Type 2 diabetes manage their condition through lifestyle changes or oral medications, but some require intensive insulin therapy. If you administer multiple daily insulin injections or use an insulin pump, you will benefit greatly from CGM. It provides immediate feedback on how insulin is affecting glucose levels, helping you optimise your doses and reduce fluctuations.

As diabetes management options become more sophisticated and our lifestyles more complicated, regular monitoring can provide extremely valuable information as to how to adjust meals, insulin doses, and various lifestyle choices.

4. People with hypoglycaemia unawareness

You may not feel the symptoms of low blood glucose (hypo), such as dizziness, confusion, or sweating. This condition, known as hypoglycaemia unawareness, can be dangerous, particularly if it leads to fainting or seizures.

CGM systems with built-in alarms can alert you when blood glucose drops below safe levels, preventing potentially life-threatening situations.

The ability to predict lows and intervene prior to them happening is of extreme value if you have hypoglycaemic unawareness. Low level alerts can be set fairly high, so that you’re able to track a descending glucose level and intervene prior to levels becoming low. Additional family members can set reminders and back-up alerts so that if you miss the alarm, they are also able to intervene.

5. Pregnant women with diabetes

Pregnancy presents unique challenges if you have pre-existing diabetes or gestational diabetes. Maintaining tight blood glucose control is essential to avoid complications for both you and your baby. CGM can provide continuous monitoring to help you and your healthcare teams adjust their treatment and keep glucose levels in check.

Recent updates to pregnancy guidelines suggest that glucose levels remain between 5.3 – 7.8mmol/L throughout the day. This is almost impossible without the use of CGM.

Additional uses of CGM with case studies

Prediabetes

Figure 2 (below) is from a patient who has not yet formally been diagnosed with diabetes. However, he has a strong genetic risk of diabetes and has been struggling to lose weight. For various reasons, he opted to try a CGM for two weeks.

Although the 4% of highs that he experienced are not high or elevated enough to diagnose diabetes, it’s clear that there is a definite rise and peak in his glucose levels after breakfast.

The band of dark and light blue shading between 6am to 10:30am also indicates the variability in his readings at this time of day. This is quite typical of mornings as many working people tend to have a smaller breakfast during the week and enjoy a more leisurely breakfast over the weekend.

A similar pattern can be seen in the evenings when various dinner choices also result in a varied response in glucose levels. Information like this can be exceptionally useful in guiding meal choices and making behavioural changes.

In addition, the results of this CGM can give valuable information if you have pre-diabetes and often helps to motivate lifestyle changes.

Figure 2: CGM download from a patient with prediabetes.

More than just an average HbA1c

Averages are exactly that – an average. As with the patients depicted in Figure 1, an HbA1c can mask many problems including variation around that average requiring a difference in medication or management.

Figure 3 (below) was taken from a patient who had an HbA1c of 7.4% which would seem to most people as perfectly acceptable. In fact, even his time in range was >70% but he was only testing his glucose levels every morning when he woke up. These readings were routinely 5 –6.5mmol/L but he was completely missing what was happening throughout the rest of the day. Fluctuations like this can lead to the development of complications of diabetes as well as affect mental and physical functioning.

Even taking random glucose levels throughout the day may have focused on pre-meal values that were also within a normal target range. The only way to “watch the entire movie” throughout the day is to see the full picture of a CGM.

Profiles such as this are worth gold to trained diabetologists and diabetes educators in terms of suggesting management changes, both to medication and lifestyle adaptations.

Figure 3: Value of CGM in monitoring variation throughout the day.

Reducing the workload of diabetes

If you know anything about diabetes, you’ll know that it is a disease that involves a great deal of hard work: checking what you eat, what activity you do, accounting for stress levels, ensuring adequate sleep, and all of this whilst juggling the many other curve balls that life throws.

Many people think that the ultimate goal in diabetes may be to get a flatline graph, but the reality is that this is generally not the norm and even a person with well-controlled diabetes will have fluctuating levels on a daily basis.

The newer integrated pump and CGM systems do a tremendous amount of modulating throughout the day as well as learning from previous outcomes and greatly reduce the impact on the person with diabetes.

Even though the average in Figure 4 (below) looks fairly stable and flat, the reality is that each day is still very variable and multiple factors influence glucose levels throughout the day. The integrated pump and CGM system are working extremely hard behind the scenes to achieve these levels and provide stability for the patient.

Figure 4: Modulations made every 5 minutes by an integrated insulin pump and CGM system.

Finding solutions to complex problems

The graph in Figure 5 (below) is what is commonly known as a spaghetti graph; the reason being that it simply looks like coloured spaghetti. It shows the variation in readings throughout each day. No day is like another.

Although this particular patient may be slightly off target, by manipulating the data on the software and focusing in on various key points, clinicians can work with patients to identify activities that have worked and others that haven’t.

Figure 5: A complex problem.

The purpose of CGM is never to find fault and blame but rather to identify areas that can be improved. To find the cause for readings that may be out of target and then implement and analyse the changes made.

Final thoughts

Whether you are caring for someone with diabetes, have a family member with diabetes, or have diabetes yourself, Type 1 or 2; young or old; on insulin or not; even if you are just at risk of developing diabetes, CGM can assist you in gaining more detailed insights into glucose patterns and improving quality of life.

Although it’s fairly costly due to the advanced technology and accuracy required to manufacture the sensors, affordable options are available, and it doesn’t need to be a 24/7/365 option. I often advise people to do a 10 – 14-day trial and then implement the learning from that time into your future behaviour. You can then continue to check-in again every month, every quarter or even just annually depending on your particular needs.

Discus your individual needs with your healthcare provider and find out if you can benefit from CGM. It has certainly revolutionised diabetes care by offering a more detailed and accurate picture of blood glucose trends and is a valuable tool for many people with diabetes.

Recent research outcomes have started to show that not only is it improving quality of life but also reducing hospital admissions, reducing complications, improving life expectancy, and the overall burden of diabetes.

Header image by FreePik