Continuous Glucose Monitors Without Diabetes: Pros & Cons

The “Glucose Goddess”, biochemist Jessie Inchauspé, gives us the low-down:

Knowledge is power (but watch out)

A continuous glucose monitor (CGM) is a device that continually monitors glucose levels, without the need to stab one’s finger every few hours to test blood.

It was designed for diabetics, especially for those with Type 1 Diabetes, where around-the-clock monitoring is necessary for appropriate insulin dosing.

For non-diabetics, they can be a good way of learning what our body’s response to various foods and activities is like, the better to be able to tweak our habits to avoid undue glucose spikes (which are harmful for our pancreas, liver, heart, brain, kidneys, and more).

How it works: there’s a sensor that sits on the arm (or elsewhere, but the arm is a popular placement) with a little probe that goes under the skin. It’s applied using a device that inserts it automatically using a needle (you only need to press a button, you don’t need to guide the needle yourself); the needle then retracts, leaving the soft, flexible probe in place. Having been attached, that sensor can now stay in place for 2 weeks (usually; depends on brand, but for example FreeStyle Libre, the most popular brand, the sensors last 2 weeks), and yes, it’s fine to bathe/shower/etc with it. When you want an update from your CGM, you scan it with your phone (or you can buy a dedicated reader, but that is more expensive and unnecessary), and it uploads the data since your last scan.

Pros: it’s convenient and gives a lot of data, so even if you only use it for a short period of time (for example, a month) you can get a very good idea of what affects your blood sugar levels and how. Also, because of the constant nature of the monitoring, it helps avoid accidental sample bias of the kind that can occur with manual testing, by testing a little too soon or too late, and missing a spike/dip.

Cons: it can be expensive, depending on where you live and what options are available for you locally, so you might not want to do it long-term (since that would require buying two sensors per month). It’s also, for all its wealth of data, slightly less accurate than fingerprick testing—that’s because it takes an interstitial reading instead of directly from the blood. For this reason, if you test both ways, you may find a discrepancy of about 3mg/dL. Given that the healthy range is about 70–140mg/dL, a discrepancy of 3mg/dL is probably not going to be important, but it is a thing to mention can (and probably will) happen.

Patterns to bear in mind (with any kind of blood sugar monitoring):

• Dawn phenomenon: a natural glucose rise upon waking.
• Exercise-induced spikes (normal due to energy demands).
• Fat in meals slowing glucose absorption.
• Different foods can sometimes cause a double-wave after dinner (because glucose from different foods is absorbed differently, and/or different foods affect insulin response independent of glucose)
• Steep, rapid spikes that are more harmful than gradual, sustained increases.
• Vitamin C spikes: temporary chemical interference with the sensor, not actual glucose rises.
• Nighttime glucose dips (often false readings caused by sleeping position).

For more on all of this, enjoy:

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Want to learn more?

You might also like to read:

10 Ways To Balance Blood Sugars

Take care!