II. Indications
- Adjunct to Glucometer and Hemoglobin A1C in Diabetes Mellitus
- Optimize Blood Glucose management in those on multiple Insulin injections per day
- Primarily indicated in Type 1 Diabetes Mellitus
- Consider in Type 2 Diabetes Mellitus with multiple daily Insulin injections or history of Hypoglycemia
III. Preparations: Needle based monitors
- Needle inserted subcutaneously and left in place for days
- Samples interstitial fluid Glucose levels (lags Blood Glucose by 20-40 minutes)
- Readings are transmitted via bluetooth to proprietary devices or smartphone applications
- Monitors will prompt users to check a fingerstick Glucose when sensor values are out of range and generate an alert
- Devices
- Dexcom G6
- Medtronic Guardian
- Sensonics Eversense
- Freestyle Libre, Freestyle Libre 2 and Freestyle Libre 3 (for age >=4 years old)
- Lower costs than other sensor/reader combinations
- Sensor (specific to each Libre model 1,2 or 3) worn on upper arm and changed every 14 days
- Freestyle Libre 2 adds alerts for highs/lows to the prior Libre 1 model (both 1 and 2 require scanning sensor with reader)
- Freestyle Libre 3 ($120/month) adds smaller size, high accuracy and transmits to smartphone app without scanning
- Sensor Site Care
IV. Management
- Time in Range (TIR)
- Measures percentage of time that a patient is in goal range (70 to 180 mg/dl)
- Prioritize correcting low Blood Sugars (Hypoglycemia) first
- Prevent Glucose <54 mg/dl and limit Glucose <70 mg/dl to less than 1 hour per day
- Goal Time in Range >70% for those with Hemoglobin A1C <7%
-
Glucose Variability (GV)
- Measures how wide Glucose values swing (35% is considered to be stable variability)
-
Glucose Management Indicator (GMI)
- Estimates Hemoglobin A1C based on the last 14 days of Glucose readings
- May vary from actual Hemoglobin A1C by more than 0.3%
V. Preparations: GlucoWatch Biographer (discontinued, listed for historical reasons and clever mechanism)
-
Wristwatch (GlucoWatch Biographer) measured Glucose through intact skin (without needles)
- Contained Glucose oxidase gel discs and electrodes, measuring Glucose via reverse Iontophoresis
- Discs converted Glucose to Hydrogen Peroxide, with a small electric current applied
- Sensor detected electrons released and reported an estimated Glucose every 20 minutes
- Disposable auto-sensors applied to back of watch provided 12 hours of readings
- Device accuracy was variable
- Required calibration with Glucometer
- Accuracy and device function was altered by perspiration and device jarring
- Measurements were less accurate for Blood Sugars below 80 mg/dl
- Skin irritation occurred with even short-term use
- References
VI. Resources
- Continuous Glucose Monitoring for Patients (NIH NIDDK)
VII. References
- (2019) Presc Lett 26(9): 52
- (2020) Presc Lett 27(9): 53
- (2022) Presc Lett 29(10): 57
