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6 step guide: non-diabetic CGM use

What to do and how to gain insights from CGM use.

Your blood sugar level is one of the most vital metrics in your body. Monitoring your blood sugar can be incredibly beneficial for athletes and non-athletes alike. People looking to lose weight, boost athletic performance, or find potential answers to ailments such as brain fog or poor sleep can all stand to benefit.

Maintaining a stable blood sugar level is a key indicator of good health and is of high interest to the ketogenic community as well. After all, a low and stable level of glucose in the blood indicates a higher level of energy produced by fats and ketone bodies.

With this 6 step guide you'll get a jump start on understanding your unique metabolism and monitoring your blood sugar response to different foods and activities.

1. Finding a CGM

A Continuous Glucose Monitor (CGM) measures blood glucose (read: blood sugar) levels throughout the day by sending real-time data to your reader or smartphone.  Getting your hands on one is no easy task as many countries (including the U.S.) require a prescription. Your options are to A) talk with your doctor to get a prescription, or B) purchase one from eBay or Amazon (you may have to purchase from an international source, more on this below*).

There are a number of CGM's on the market to choose from. In our experience the 14-day FreeStyle Libre from Abbott works best. There are few reasons for this:

  • Abbott's 14 day sensor is mobile compatible (no need to buy a separate reader, your Android or iOS device will do**).
  • Libres are commonly sold on eBay and Amazon.
  • The Libre is super easy to put on.
  • The Libre is the most widely used in the biohacking community.

The FreeStyle Libre sensor is about the size of a coin and is worn on the backside of the upper arm. The sensor is water proof and lasts for 14 days. The sensor has a thin filament that goes just underneath the skin and reads blood glucose levels from the interstitial fluid.

*FreeStyle Libre CGM's are sold without prescription in Canada and Germany and can easily be found for sale on eBay or Amazon in those markets. Note however that a FreeStyle Libre sensor purchased in one geographical market may not work with readers or applications downloaded in another geographical market. To get around this, you will have to switch your app store location to the same country from which the sensor was purchased.

**Must be iPhone 7 or higher (running iOS 11 or higher) OR Android 5.0 (Lollipop) with NFC capability.

2. Applying the sensor

Applying the FreeStyle Libre sensor is pretty simple. This video shows how it's done:

Remember that after applying your sensor, and scanning for the first time, you will have to wait for 60 minutes before getting any readings (the sensor is programmed to equilibrate during that time to allow for more accurate readings). Also note that there is no need for the reader shown in the video, using the FreeStyle LibreLink app on your mobile will suffice. More on that in Step 4 below.

3. Setting goals

What's your main objective for wearing a CGM? What type of insight would you like to gain? Having a clear plan of attack before starting can help you take a more empirical approach to wearing your CGM, leading to more valid and genuine findings.

In our experience, some of the biggest insights from CGM use come from understanding how different foods impact blood sugar. Should you eat a big bowl of oatmeal in the morning or bacon and eggs? What should you eat for lunch to avoid that after lunch crash?

You will for instance, see a marked difference in post meal blood sugar following a high carb meal vs a low carb meal. Additionally you may realize that certain foods, while problematic on their own, may cause no problems when consumed with other foods that slow digestion (e.g. foods higher in fat or fiber). Take note that blood sugar response patterns are highly personal. A certain food may trigger a huge spike for you and just a blip for your friend.

Or maybe you're an athlete, looking to boost your athletic performance. From your CGM use you might find that you just feel better training during periods of higher blood sugar. Your strength is a bit more explosive, your mind is a bit clearer, and putting in that last mile feels just a little bit easier. In that case, opting to time your workouts for periods of the day when your blood sugar tends to be higher makes a lot of sense (either naturally because of your circadian alignment or by design because of your eating schedules).

If you're looking to lose weight, you can use a CGM to identify certain foods, portion sizes, and/or meal timing that cause spikes or prolonged high blood sugar, and take action accordingly. You may find for instance, that following a 16/8 fasting schedule timed for later in the day is easier for you to follow, thanks to naturally high blood sugar levels (and better energy) in the morning hours. In any case, glucose is the primary fuel source for your body. Have too much of it and weight gain results. Data on its levels and fluctuations can be huge for helping you manage your weight.

Generate goals that are aligned with your longer term ambitions. Whether you're looking to optimize performance, troubleshoot metabolic disorders, or in general learn more about your body, think past the two week sensor-wear period, and consider how your blood sugar is impacted by or may impact, different aspects of your life. The suggestions above are by no means an exhaustive list but rather a place to start!

4. Installing the right applications

LibreLink for blood sugar

First things first, in order to scan your FreeStyle Libre sensor and save your blood glucose data you'll need to download the FreeStyle LibreLink application. This app will be your number one tool. Make sure to download the app from the app store of the same country from which you purchased your sensor (the sensor and app specifications vary from country to country based on local laws, so a sensor purchased in one country may not work with the FreeStyle LibreLink app downloaded in another).

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Additionally, in order to obtain meaningful insights from CGM use, you will want to track and collect data on aspects of your lifestyle you suspect may impact or be impacted by your blood sugar levels. A few apps we’ve found to work well:

Lifesum for nutrition

With Lifesum you can relatively easily track your diet. You can scan or search for foods to log your meals, and Lifesum automatically calculates the number of calories as well as a breakdown of the macronutrients consumed. Lifesum unfortunately does not allow for time stamping of meals, but to date it still seems to be the best available food tracker.

Strong for strength training

Use Strong to easily quantify your strength training routines. The free version offers all needed functionality.

Strava for cardio

Strava is perfect for quantifying your running, biking, or swimming activities.

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The following apps are a big bonus if you can afford them. Both require the purchase of additional hardware but come with the upside of automation.

Oura for sleep

Oura is without a doubt the best consumer sleep tracking device that exists. Oura not only offers highly detailed metrics on sleep such as deep sleep, REM sleep, and sleep start/end times, but also gives data on resting heart rate, HRV, and body temperature deviation. All of this automatically just by wearing a ring.

Health Mate for body composition

Healthmate from Withings works paired to a smart scale. Simply use the scale, just like any other scale, and it automatically sends a record of your weight, body fat %, muscle mass, and bone density to your Healthmate application.

Don't be afraid to think outside the box. If you suspect something else in your lifestyle might be affecting or be affected by your blood sugar go ahead and track it! Apps and metrics that can be automatically tracked will make your two week trial a lot easier, but don’t hesitate to use more conventional methods as well. More on making sense of your collected data down below in step 6.

5. Scanning and tracking

With sensor on hand and apps downloaded let the games begin! A few things to keep in mind to make sure everything goes smoothly:

Scan your sensor first thing in the morning

The FreeStyle Libre sensor can only hold 8 hours worth of blood sugar data before it starts deleting and rewriting over data. This means you should scan your sensor at a minimum at least once every 8 hours. Scanning your sensor first thing in the morning is a good habit to make sure you collect as much of the previous night's data into the LibreLink app as possible.

Scan your sensor before eating

Most food tracking apps, Lifesum included, do not include time stamps for meals. By scanning your sensor right before starting a meal, you are automatically creating a time stamp into the LibreLink app. This makes interpreting your data much easier later on.

To make things extra clear for yourself, once you have scanned your sensor, tap on the reading and select "Add Note", then tick the box labeled "Food". Next you will of course want to log your meal into Lifesum or your food tracking app of choice.

Track your activities of choice

If you decided to track more than nutrition remember to do so! Staying consistent and up-to-date with tracking is important. Incomplete data will make it next to impossible to draw any meaningful conclusions. Log each meal, each workout, or whichever variable it is that interests you, in as much detail as possible.

Scan your sensor before going to sleep

Remember, the FreeStyle sensor only has storage capacity for 8 hours of glucose data. Scanning right before sleep ensures that as much of your sleep glucose data gets recorded as possible.

Make note of anything peculiar

All time highs or all time lows. If you catch an event that seems out of the ordinary, document it well by adding an additional note into the reading of the FreeStyle LibreLink app. This way you won't forget and be caught wondering what that blood sugar dip was all about two weeks later.

There are a ton of variables that can impact your blood sugar. From our experience, most effects however can be tied to what happens in your kitchen, at the gym, or in bed. Depending on your goals and area of interest make sure to track meticulously, especially when it comes to nutrition. It can be quite tedious, but trust us, it's worth it for even a small glimpse into better understanding your metabolism.

6. Analyzing the results

Analyzing your results is arguably the most challenging step. It's far too easy to misinterpret data and to draw misinformed conclusions. Take note that wearing a CGM should be seen as a means to bring heightened awareness to your wellbeing, not to diagnose or cure any existing disease.

First you will need to aggregate all of your data! Start by logging into the LibreView website with the same credentials you used for your FreeStyle Libre application. Then click on this icon in the top left:

Then you can select "Glucose Reports" and view some of the prebuilt charts Abbott provides for you. Although fun to look at, these are not likely to yield any novel insights. For the real meat and potatoes you will have to press "Download Glucose Data" from the top right:

You'll automatically get a downloaded .csv file of your blood glucose in either mmol/L or mg/dL for every 15 minutes of sensor wear. Should look something like this:

Then download an app called QS Access. With QS Access you can easily download all of the relevant health data that you have been tracking in step 4 and 5 into one .csv. Note that you must enable all of your tracking apps to write data to Apple Health (or Google Fit) for this to work. You'll end up with a table of datestamps and the metrics of your choosing e.g. calories burned, steps taken, macros eaten, current weight etc. After that, pull your health data from QS Access together with your blood sugar data from the LibreView portal and start comparing!

You can start by calculating daily blood sugar averages, running simple CORREL functions between different variables and your blood sugar, or graphing your blood sugar data over a specific variable. Alternatively, if you see something interesting in your data, such as an especially high blood sugar day, jump in and take a closer more granular look at that particular day. Go back into your food, sleep, or activity tracking apps and try to paint a clear picture of what happened that day. Did you sleep poorly? Were you stressed? Was your eating schedule out of the ordinary? The main goal of wearing a CGM is to highlight potentially negative or positive aspects of your lifestyle and bring them to your awareness. Treat the data as a supplement and tool for doing just that.

Ultimately, the purpose of pulling together all of your data is to get a wholistic picture of what's going on. Two weeks of data is not much, but it can give just enough of a glimpse to help you start tweaking and optimizing your lifestyle. Look for more on the data science of analyzing your results in a future blog post.

Happy experimenting!

Hopefully this post serves as an outline of things to consider and keep in mind for CGM use. If you have any questions or concerns please reach out to us at

Happy hacking and remember to enjoy the process!

Further reading