Summary
Measuring blood glucose levels in participants has important applications outside of diabetes research. It can be useful in understanding how metabolic changes affect mood and mental health, how it impacts exercise recovery and athletic performance, etc. Researchers who require glucose measurements have several options, including continuous glucose monitors, connected meters, and more. This article lists some of the common glucose meters being utilized by U-M researchers, as well as upcoming devices, as of late 2024. It also discusses factors to consider when selecting a glucose meter for research.
Note: The Eisenberg Family Depression Center does not recommend any specific brands or devices
Device List
Prescription-only Continuous Glucose Monitors (CGMs):
- Abbott Freestyle Libre 2 - 14 days, worn on arm, records every minute, reading range 40-400 mg/dl
- Abbott Freestyle Libre 2 Plus - 15 days, worn on arm, records every minute, connects to t:slim x2 insulin pumps
- Abbott Freestyle Libre 3 - 14 days, worn on arm, records every minute
- Abbott Freestyle Libre 3 Plus - 15 days, worn on arm, records every minute, compatible with certain insulin pumps
- Abbott Freestyle 14-day - 14 days, worn on arm, records on-demand
- Note: this device does not transmit data continuously. It requires manually scanning the sensor by touching it with the phone's NFC sensor
- Dexcom G6 - 10.5 days, worn on abdomen (adults) or buttocks (young children), compatible with certain insulin pumps
- Dexcom G7 - 10.5 days, worn on arm (adults), abdomen (adults, Europe only) or buttocks (young children), records every 5 minutes, compatible with certain insulin pumps and smart insulin pens
- Medtronic Guardian Connect CGM System (Guardian Sensor 3) - 7 days, worn on abdomen or arm, records every 5 minutes. For use with MiniMed pumps and Guardian Connect System only
- Medtronic Simplera - 6 days, worn on arm, integrates with InPen smart insulin pen, Medtronic Smart MDI, and MiniMed pumps (via Simplera Sync sensor, pending FDA approval)
- Senseonics Eversense E3 - 6 months, subcutaneous implantable sensor plus transmitter worn on arm, records every 5 minutes, reading range 40-400 mg/dl
- Senseonics Eversense 365 - 1 year, subcutaneous implantable sensor plus transmitter worn on arm, records every 5 minutes, reading range 40-400 mg/dl
Over-the-counter Continuous Glucose Monitors / Biosensors (OTC CGMs, Glucose Biosensors):
- Dexcom Stelo - for healthy lifestyle and weight management; 15.5 days, worn on arm, records every 15 minutes
- Abbott Lingo - for healthy lifestyle and weight management; 14 days, worn on arm, records every minute, reading range 55-200 mg/dl
- Abbott Libre Rio - for consumers with Type 2 Diabetes who are not on insulin
- There maybe other OTC CGMs in the market but without FDA approval
- Note that the FTC and FDA have warned consumers against using smartwatch-based "glucose monitors" since none have yet been cleared by the FDA and there is currently no data backing their performance and safety.
Over-the-counter Bluetooth-enabled Blood Glucose Meters (BGMs / Glucometers):
Over-the-counter BGM Apps:
Selection Considerations
The following considerations can help when selecting the best type of glucose measuring device for a study.
Measurement Type
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Interstitial Glucose. Measurement of the glucose content in interstitial fluids (fluids between the cells), often called Estimated Glucose Value (EGV) because it is not a direct measurement of blood glucose. Used by CGMs.
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EGVs can lag behind true blood glucose by 15 minutes, but the application method makes it more convenient and may increase participation compliance.
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Values can also be affected by putting pressure or body weight on the application site (compression lows), FDA label vs. off-label application sites (typically approved for back of arm, abdomen, or upper buttocks), and body acclimation (where values could be inconsistent or less accurate during the first and last 24 hours of sensor lifetime).
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Sensor accuracy can be estimated by MARD values, where lower values are closer to lab-measured values within a specific frequency. Some brands can be calibrated using user-entered blood glucose values, which may bring EGVs closer to the user's meter.
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Blood Glucose. Measurement of capillary blood glucose. Used by BGMs and BGM apps.
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Values can be impacted by the accuracy of the meter, testing site (finger, palm, forearm), test strip age or batch properties, and other factors.
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Meter accuracy varies from brand to brand and even model to model, but ISO-compliant and FDA-approved meters must meet a specific accuracy criteria.
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Other. Note that there are currently no FDA-approved glucose meters that do not penetrate the skin, and the FDA has warned consumers against using smartwatches that claim to read glucose levels via photosensors. However, researchers should be aware of upcoming advances in non-invasive glucose sensors utilizing PPG, radio frequency and/or electro-dermal activity. Several companies are working on clinical trials for these new types of sensors.
Measurement Rate
- Continuous. Different CGMs provide measurements at different rates, most commonly every minute (e.g. Freestyle Libre 2 / 3 / 3 Plus, Lingo), every 5 minutes (e.g. Dexcom G7, Eversense E3 / 365), or every 15 minutes (e.g. Dexcom Stelo). Note that earlier versions of CGMs, sometimes marketed as "touch" or "intermittent", do measure glucose continuously but require the user to touch the sensor with a reader or smartphone to get a value.
- Devices: CGMs, except those labeled as "flash", "touch" or "intermittent" (e.g. Freestyle Libre 14-day).
- Intermittent. Participants must measure on-demand (e.g. by finger prick or sensor tapping).
- Devices: BGMs, CGMs labeled as "flash", "touch" or "intermittent".
Integration with Other Devices
- Integration with Insulin Pumps. In populations that are insulin-dependent, integration of CGMs/BGMs with insulin pumps is important to ensure participants do not need to wear additional or incompatible devices.
- Some CGMs and BGMs can integrate with insulin pumps, either in open-loop (manual insulin delivery) or closed-loop (automated insulin delivery, or AID). Integrations are dependent upon manufacturer partnerships and product lines. Examples include:
- Insulet Omnipod 5 with Dexcom G6 / G7
- Insulet Omnipod DASH with Ascensia Contour Next ONE
- Tandem Mobi with Dexcom G6 / G7
- Tandem t:slim X2 with Dexcom G6 / G7 or Abbott Freestyle Libre 2 Plus
- Not all insulin pumps can integrate with CGMs or BGMs at all (e.g. Ascensia Eversense E3 / 365)
- Some insulin pumps may include a remote with built-in BGM (e.g. Accu-Chek Combo, Accu-Chek Solo, Dana Diabecare R)
- Always check the compatibility list provided by the manufacturer.
- Integration with Other Insulin Delivery Devices. Similar to open-loop pump integration, some CGMs and BGMs can integrate with apps for smart insulin pens, smart pen caps, smart pen buttons, or smart injection ports to help determine dosing adjustments and suggestions.
- CGM-BGM Integration and Calibration. Integration between CGMs and BGMs is not necessary, but can be helpful for ease of use and to avoid errors in manual entry of BGM values.
- Some CGMs require periodic calibrations with a BGM finger prick reading (e.g. Eversense E3 / 365, Medtronic Guardian Sensor 3). Others make calibration optional (e.g. Dexcom G6 / G7), while some do not have the option to calibrate manually (e.g. Freestyle Libre 2 / 2 Plus / 3 / 3 Plus). However, current CGM-BGM integrations only allow logging BGM readings but do not automatically use those values for calibration. The readings must still be entered manually by the user in the calibration screen of the app.
- Most (if not all) CGM manufacturers recommend checking glucose levels with a BGM finger prick when symptoms do not match EGV readings, when a trend arrow is not available, or when readings are below or above the devices range.
- Some CGMs have an optional receiver with a built-in BGM (e.g. Freestyle Libre 14-Day / 2 / 2 Plus / 3 / 3 Plus Receivers). Others are compatible with specific BGM brands or apps. All CGM apps allow recording values manually, but for data integrity and accuracy during a research study, manual entry of glucose values should be avoided.
- Integration with Health Monitor Devices. Some BGMs are built into blood pressure monitors, smartwatches (e.g. EASYMAX sugarwatch), and other health monitors. This allows recording for glucose, blood pressure, spo2, activity, etc. in a single app and through a single service. The same can be accomplished by syncing to data aggregators like Apple Health, Google Fit / Health Connect, Samsung Health, Glooko, and others. Participants may find it convenient to have a single device for several health measurements.
- Transmission to Multiple Receivers. Although data can oftentimes be viewed in multiple receivers, sometimes that data only lives in the sensor (for a few hours) and the primary receiver.
- Some CGMs can only pair and transmit data to a single receiver during the lifetime of the sensor, whether that's a smart phone or external receiver unit (e.g. Freestyle Libre 2 / 3, Eversense E3 / 365). Any other device is considered a "secondary display" and does not communicate with the sensor directly. This means the data only exists in one receiver until synced to the cloud.
- Other CGMs can pair with and transmit data to multiple devices, such as smart phones, external receiver units, smart watches and insulin pumps (e.g. Dexcom G6 / G7, Freestyle Libre 14-day). This can potentially add a backup recording method when the primary receiver/syncing device is out of range or turned off for longer than the sensor can store values in memory.
- Similarly, some BGMs allow pairing with multiple phones/pumps, while others require un-pairing and re-pairing when connecting to a new device.
Body Placement
- Body Placement / Sampling Area. Each device manufacturer specifies the body areas on which their device can be used, which can sometimes vary by geographical region based on what the local regulatory body has approved. This can be important when working with pediatric populations.
- Abdomen:
- BGMs - None
- CGMs - Dexcom G6, Dexcom G7 (only adults in Europe), Eversense E3 / 365, Guardian Sensor E3
- Back of Upper Arm:
- BGMs - Accu-Chek Guide / Guide Me
- CGMs - Dexcom G7 / Stelo, Eversense E3 / 365, Abbott Freestyle Libre 14-Day / 2 / 3 / 3 Plus / Rio, Abbott Lingo
- Finger:
- BGMs - all BGMs
- CGMs - None
- Forearm:
- BGMs - Evencare G2 Bluetooth
- CGMs - None
- Palm:
- BGMs: Accu-Chek Guide / Guide Me, Countour Next GEN / ONE, Evencare G2 Bluetooth
- CGMs - None
- Upper Buttocks:
- BGMs - None
- CGMs - typically reserved for young children only
- Wrist:
- BGMs - EASYMAX sugarwatch (reader is worn on wrist but finger pricks are still done on fingers)
- CGMs - None
- Off-Label Uses: Medical professionals sometimes recommend different placement areas depending on individual circumstances. Such uses would be considered "off-label" and may void manufacturer warranty.
- Body Placement Type / Invasiveness. Currently available CGMs and BGMs require a certain degree of invasiveness, which varies by how they are placed or used.
- Skin patch with needle. The CGM sensor contains a small needle that penetrates the skin. An applicator is used to apply the sensor while pushing the needle. Most CGMs in the market work this way, except Eversense E3 / 365.
- Subcutaneous insert with skin patch transmitter. The CGM sensor is implanted under the skin by a healthcare professional, and a transmitter patched is placed on the skin directly on top of the insertion site. Currently only Eversense E3 / 365 work this way.
- Skin prick for capillary blood collection. This is the most common blood sample collection method and used by virtually all BGMs.
- Venous puncture for venous blood sample. This is typically supported by BGMs designed for clinical use only.
Data and Technology Considerations
Some popular insulin pumps may not have Bluetooth connectivity or APIs to access their data directly. However, there are some apps that could provide a bridge to Bluetooth and the cloud, sometimes requiring specialized USB adapters or RF conversion dongles. If such third-party apps and/or bridge devices are not officially approved by the manufacturers, researchers should consider other options to help ensure participant safety and data integrity.
In addition, there are some brand-specific considerations to keep in mind:
- Abbott Freestyle Libre apps do not currently integrate with Apple Health, Google Fit / Health Connect, Samsung Health, or with diabetes management platforms like Tidepool and Glooko. However, researchers can setup a "clinic" free of charge at the LibreView service, which allows them to remotely view and download participant's data.
- Omnipod 5 insulin pumps currently only has direct, official integrations with Glooko.
- Many Bluetooth BGMs only sync to their own app, but will typically support sending the data to Apple Health, Google Fit, Health Connect or select third-party APIs.
Notes
- The Eisenberg Family Depression Center does not recommend any specific brands or devices. The information in this article is purely for informational purposes only.
- If you are using other devices in your studies, please let us know in the comments.
- Other OTC CGMs maybe available but do not (yet) have FDA approval.
- The list of FDA-approved, Bluetooth-enabled CGMs and BGMs is constantly growing. Please help us improve this article by letting us know of new devices through the comments or by emailing the Mobile Technologies Core.
About the Author
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Gabriel Mongefranco is a Mobile Data Architect at the University of Michigan Eisenberg Family Depression Center. Gabriel has over a decade of experience in data analytics, dashboard design, automation, back end software development, database design, middleware and API architecture, and technical writing.
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