You don't have to miss out: A CGM guide

Continuous Glucose Monitors to unlock metabolic health

When I first started practicing medicine, the only time I could obtain a continuous glucose monitor was on a patient with fragile type 1 Diabetes, to have an intricate understanding of how to dose their insulin daily. But today, that’s not the case. These monitors are not only much more accessible, they are more useful than we understood.

Today, I want to give you an understanding of what these devices are, who could consider using them and why.

I consider them a gateway for my patients to personalized nutrition and metabolic health.

---

What are Continuous Glucose Monitors?

Continuous Glucose Monitors (CGMs) are basically small wearable sensors that you can implant under your skin and allow you to see glucose levels every few minutes. The sensor is applied, usually to the back of your arm, with a needle. When the needle is removed, the sensor is left in place, typically for 14 days. (For all the needle averse out there, you hardly feel it going in!)

Typically the sensor takes 30-60 minutes to “warm up” meaning it’s then ready to report levels. You will connect it via bluetooth to a smartphone and have an app that reports the sugar levels to you. This app will also have alarms that sound if your glucose goes too low or too high.

How they work: When you insert the monitor, it is essentially a filament that measures glucose levels in the interstitial fluid (the fluid around your cells). In this way, it is a proxy for blood glucose levels. It’s possible then that there is a slight lag in the level as compared to a fingerpick you might use at home if you have diabetes. I would not worry about this too much but mention it only if you also validate it with finger prick testing and want to understand why there is slight variation.

Do I need a precription? Yes, in the US, if you want to use one of these you will need a prescription from your physician. Usually, insurance companies will only cover this cost for diabetes, type 2 diabetes, pre diabetes, and sometimes a diagnosis of insulin resistance.

Even if you don’t have one of those conditions, I would advocate to your physician to write you a one-time prescription so that you can work on prevention and/or optimization of your metabolic health. You won’t be able to get it covered by insurance but you will be able to get the device.

It’s not cheap but it’s also way more accessible than it used to be. This was never even an option for my patients two decades ago. The type I use the most is Freestyle Libre and it costs somewhere around $65-100 for a two pack supply depending on your pharmacy, and if you get a coupon (definitely ask your pharmacy for this!). In my clinical opinion, even using one for two weeks will give you such great insights that it’s a wonderful investment for your metabolic health.

There are also emerging programs constantly that allow you to purchase a membership and get CGMs through them without a prescription but these are more costly because they include coaching and consultation with the program. The one that I knew best was just acquired by Oura, a wearable sleep device, so you can see how big this tool for metabolic health is getting. It’s being integrated into many prominent tracking devices.

---

Why consider using a CGM?

You may be thinking that you don’t need this device because you don’t have diabetes or even pre-diabetes. But I want to encourage you to think more broadly about how this device could be used.

For one, let’s peek at the emerging science around glucose metabolism and homeostasis. We know now that it’s not universal that you will respond to food the same way as another person. Much of this depends on your particular gut microbiome which plays an essential role in converting fiber and other non-resistant starches in the gut to short-chain fatty acids (SCFAs). These then play an essential role in glucose homeostasis.¹ This is one reason why you may spike higher than someone else when you eat the same exact food. To get to know your individual, unique glucose response, using a CGM can be powerful.

We also know that bacteria that produce these SCFAs such as butyrate have a protective effect against type 2 diabetes.² This is powerful science because it helps us understand why gut health is so important but also helps us see why individualized nutritional approaches can be so helpful.

Biofeedback helps you make more predictive habit changes. Having a CGM on can be like any other wearable in that the information becomes data for you to understand your body better. Keeping track of your food, exercise activity and stress levels during a 2 week stint of using a CGM can help you guide your lifestyle choices in a more useful way.

The scientific pillars that I find most helpful for metabolic health prevention from a CGM are…
🥗 Nutritional approaches
💤 Sleep health
🏋🏽‍♀️ Physical Activity
😩 Stress (Spoiler alert: its impact on blood sugar is BIG)

Here’s the thing: In conventional western medicine, prevention is often just watching and waiting.

I was taught in residency to measure hemoglobin A1C levels (a composite of your 3 month blood glucose levels) and if it was in the pre diabetic range (5.7%-6.4%), to tell your patient to watch their diet and check it regularly to see if and when it gets in the diabetic range.

This is NOT prevention to me. This is waiting for disease.

In contrast, if my patient’s HgA1C level is nearing 5.7, I start talking to them then about prevention and the four pillars above so we can make tailored interventions. I can talk more about lab work in our workshop at the end of the month but suffice it to say, I don’t want you to wait for disease, I want you to prevent it from coming your way. And I talk about metabolic health with all patients because it’s THAT important.

The kinds of changes you can make from CGM data:

• You can experiment with how fasting 12-13 hours impacts your glucose levels

• You can see how your blood sugar changes if you eat the same meal, but in a different order: i.e eating protein before or after the carbohydrates, etc

• You can see how your blood sugar changes if you exercise or take a walk after or before a meal.

• You can see in real time what stress does to your blood sugar and in turn, what happens if you do some relaxation practices.

• You can see what happens to your blood sugar levels if you get a poor night’s sleep.

• You can see what happens with different meal options, such as breakfast. Maybe you think oatmeal is a healthy option but then you see your blood sugar soar after eating this. (This is very common) And then you can see if that changes if you add nuts and seeds or other ingredients to the oatmeal.

You can tell from this list (and it’s only a start!) how much I love using CGMs for the important lifestyle interventions you need for metabolic health.

Who should think of using a CGM?

If you have diabetes, pre-diabetes or insulin resistance, a prescription from your physician will often be covered by insurance for a CGM, and for good reason. Sometimes, obesity will be enough of a diagnosis but not always in my experience.

In addition to this, if you have other signs of metabolic syndrome, even if you don’t qualify for the full diagnosis, I would consider asking your physician for a prescription. Remember we went over what constitutes metabolic syndrome in last week’s article if you want to go back and review that.

I personally think if you are having trouble losing weight, it’s a good thing to consider. Often the plateau lies in glucose metabolism and getting a better understanding of how your body is reacting and to what will give you some crucial information to make change.

I advocate for all of my patients who have a family history of high cholesterol, high blood pressure, or heart disease to consider this as powerful step in helping them prevent disease. I can’t get insurance to cover it for this reason (which frustrates me!) but at least we can make changes in their health that matter. Globally, cardiovascular disease is the number one killer and so I find it hard to not find a good reason for my patients to use this powerful health information. I wish it were more affordable and my hope is that it becomes more and more accessible. As I said before, this wasn’t even an option when I started practicing medicine unless you had type 1 diabetes with an insulin pump.

I consider CGMs a wearable tracker, just like a Fitbit or Oura ring for example, although a CGM is temporary. Regardless, it provides useful information for me to help patients tailor their lifestyle choices to their individual constitution and microbiome. Even just once, it’s a good investment for your longer term health and can often give you what you need to understand why you feel a certain way at certain parts of the day.

Maybe you’re always in a ‘food coma’ in the afternoon or you are more jittery at another part of the day. You might find out your sugar is spiking or dipping low for reasons that you can adjust. Remember that anxious feelings also can arise from low blood sugars for example. My favorite metric is showing patients how their post-meal glucose changes with a simple walk. Seeing how powerful this intervention is really helps my patients see how important it is and that makes the habit easier to stick to!

I love getting this information for my patients and then tailoring their habits with them. And I hope you might consider this for yourself. Let me know all your questions and share your own stories of using a CGM if you’ve done so. The whole community will benefit from hearing from you! And on Saturday April 26th remember we have an Ask-Me-Anything about Metabolic Health for paid subscribers and I’ll also tell you the lab tests I advocate you ask for! I will send out this zoom link next week.

1. Portincasa et al. Gut Microbiota and Short Chain Fatty Acids: Implications in Glucose Homeostasis. Int J Mol Sci. 2022 Jan 20;23(3):1105.

2. Sanna et al. Causal relationships among the gut microbiome, short-chain fatty acids and metabolic diseases. Nat. Genet. 2019;51:600–605.