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  • Writer's pictureGemma Westfold

Is it worth you trying a CGM?

Updated: May 6


You’ve probably seen people online talking about continuous glucose monitors (CGMs). Perhaps you might well have spotted people wearing a little white disk on their upper arm and wondered, what’s that all about?  If you want to know how all of this relates to you and whether you should invest in one, read on.

What do these devices do?

The reason people are using these devices is that they want to know what their blood sugar levels are. For some, this is a medical necessity. They may have been told they have type 2 diabetes and want to get back in control of their glucose levels or, for type 1 diabetes, they need real-time information to work out how much insulin they need to dose. Since very high sugars are dangerous to the body and very low sugar levels (hypos) can be life-threatening, these monitors can mean the difference between life and death.

Over the last couple of years, more and more people who are simply interested in their health are investing in them. These might be people who have been told they have prediabetes and who want to reduce the risk of developing type 2 diabetes, or those who are looking for answers to why their energy is lacking, or they’re struggling to lose weight, or maybe even those people who love getting data on what their body is doing.

If you follow me then you know that I am very keen on managing blood sugar levels as it is a massive piece of the puzzle in managing energy, immunity, hormonal health, weight and sleep.

Fasted Glucose Blood test

Your doctor may routinely have taken a fasted reading like this if you’ve ever had blood taken. It’s considered a reasonable measure of your blood sugar levels but the essential thing to note is that it is just one moment in time – literally the time of the blood draw – and it might have been different yesterday and it might be different tomorrow. This is why having a CGM can be helpful, and it is also why doctors who are genuinely interested in what your blood sugar levels have been doing over time would test your HbA1c.

HbA1c stands for haemoglobin A1c, which is a blood test used to measure the average blood sugar levels over the past three months. Haemoglobin is a protein found in red blood cells that carries oxygen to different parts of the body, and glucose can attach to it, forming a "glycated" haemoglobin molecule.

The HbA1c test measures the percentage of glycated haemoglobin in the blood, reflecting the average blood sugar levels over few months. It is literally how much sticky sugar has stuck to your blood cells. This is why it’s more interesting for medical professionals to know what this number looks like for their patients rather than a single measurement taken on the one day they were in the blood test centre. You can get your HbA1c done privately and relatively inexpensively. It’s a test I always do with my clients and one we often target to lower. I have had lots of success here and clients tend to be very much onboard when the possibility of type 2 diabetes is looming. If you haven’t had a recent Hba1c then I suggest you ask your GP. If it is 42 or over then that indicates pre-diabetes, and 48mmol/L If you want to do it privately then you can ask me.  

What do Hba1c readings look like?

  • 42mmol/mol to 47mmol/mol indicates prediabetes (insulin resistance)

  • 48mmol/mol plus indicates type 2 diabetes (according to NICE guidelines).

In reality, I like to take action if it gets over 37mmol/mol by making nutritional and lifestyle changes to prevent the devastatingly poor health associated with high amounts of glycated haemoglobin.


What do blood glucose readings look like?

  • Morning fasting glucose levels should be between 4mmnol/L and 5.4mmol/L (72 to 99 mg/dL) for non-diabetics.

  • 5.5 to 6.9 mmol/l (100 to 125 mg/dl) may be indicative of prediabetes.

  • 7.0 mmol/l or more (126 mg/dl or more) may suggest diabetes.

Continuous glucose monitors (wearable blood glucose monitors)

When you see someone wearing a little disc attached to their upper arm, chances are it’s a continuous glucose monitor (CGM) or, more specifically, a related device called a flash glucose monitor (FGM). The two terms are used interchangeably although there are some very subtle differences in the way they fetch their readings.

Both devices are designed to monitor blood glucose levels. A CGM continuously tracks glucose levels in real-time and provides continuous updates to the user throughout the day and night. It can also talk to insulin pumps.

In contrast, a flash glucose monitor (like the popular brand FreeStyle Libre), takes some automatic readings but it also requires the user to scan a small sensor worn on the skin with a reader or a smartphone app to get the glucose readings. The readings are stored on the sensor and can be reviewed later to get a general idea of glucose trends over time. It can only store eight hours of data, so users typically have to ensure they scan before bed and shortly after they get up just to make sure readings have been taken and there are no gaps in data. Working with me, I also get a copy of this data straight to a reporting tool I use.

If you are diabetic, you might be entitled to a device on prescription. If you are simply interested in your metabolic health, you will not. You can also buy the FreeStyle Libre device from selected pharmacies and also the manufacturer Abbott direct. Monitors last 14 days and cost around £55.

The important thing to note about these monitors is that they can be a great tool for understanding your individual blood sugar responses to food, exercise and stress but they are only a part of the puzzle. I use them often with clients and I get a report that shows me what happens in your blood (which I share with the client), but it doesn’t show what insulin is doing and it doesn’t show me stress levels, lack of sleep etc. This is why it is so important to interpret these monitors along with symptoms and lifestyle.

If you are interested in doing this with me, if you have been recently diagnosed as prediabetic or you have type 2 diabetes and you want to get ahead of it then I will happily put together a few sessions where we can discuss your goals and what may be impacting your blood sugar (and therefore your energy, sleep, immune system, hormones etc).

I recommend using these when there seems to be blood sugar dysregulation – when someone gets very tired after eating or when someone gets incredibly energised after eating then very tired two hours later. I use them when someone is pre-diabetic and diabetic, hypoglycaemic, craving sugar all day and only feeling better after having it or when someone wants to prevent a family history of metabolic concerns.

Interested? Book a free 20 minute Reboot your Health call and we can discuss the options.

How I can help with Nutritional Therapy

Using the functional medicine approach, I work to understand why your imbalanced blood sugar. You can expect from me:

  • A personalised nutrition plan rich in nourishing foods to assist your bowel function

  • Test recommendations and full interpretation either privately or through your GP

  • Personalised supplement protocol to support your digestive function

  • Regular consultations and coaching to support new choices

Note: as a Nutritional Therapist, I do not diagnose or prescribe, however I do use functional nutrition testing to help find the best way to support my client’s health.


My programmes are designed with people like you in mind. I see many clients with fatigue, gut health issues, autoimmunity etc. and they all have different symptoms, family health histories, lifestyles, work and family life which may may have contributed to where they are. This is why a personalised nutrition and lifestyle rather than a 'one size fits all' gets such good results. Book your free Reboot your Health 20 minute call to discuss your health goals and if working with me would benefit you.

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