You can reserve/ schedule a CGM unit insertion visit follow by a download visit ~ 7 days after insertion. We only do this on Mondays, Tuesday or Thursdays. We do not insert or download CGM on any other days. Expect to spend 45-60 minutes in our clinic for these visits and allocate this time in your schedule. We encourage you to read the online tutorial before insertion. If lost or damage, you will be responsible for replacement of transmitter and the receiver. The sensor is disposable.
What is CGM?
Continuous glucose monitoring (CGM) systems use a sensor inserted under the skin to detect glucose level in tissue fluid (called interstitial fluid). A transmitter sends information about the user’s interstitial glucose level via wireless technology to a receiver. Glucose levels in interstitial tissue often lag by between 5-15 minutes behind actual blood glucose levels (Lag-times vary). As a result, CGM must be calibrated with a traditional blood glucose measurement at least three times per day.
Continuous glucose monitoring systems display real-time interstitial tissue glucose readings. This allows you to:
- View current interstitial glucose level,
- Glucose graphs
- How fast and in what direction your glucose level is heading, allowing early intervention to reduce the frequency and severity of glucose episodes.
- See how day-to-day living – diet, exercise, medication and lifestyle affect your glucose level.
- find out any ‘hidden’ problem periods in your 24-hour glucose patterns, or to decide the best system to meet your needs.
Depending on the system used there are a variety of alerts and graphs such as:
Real-time readings displayed every few minutes
- Alerts providing early warning signals to avoid or minimize oncoming lows and highs
- Alerts to show when glucose levels are changing
- Real-time graphs to show previous glucose readings
- Real-time trend arrows and alerts to show the direction of your glucose level
- All can be downloaded to produce additional graphs and data
Sensor and transmitter
The sensor is comparable to the size of an infusion set – with a similar sized needle, and the transmitter fits snugly onto the sensor.
Who Can Benefit from Continuous Glucose Monitoring?
- Adults and children with Type 1 or Type 2 diabetes
- People whose glucose level is outside of the normal range, not yet diagnosed with diabetes or other medical conditions
- People with diabetes who have lost the ability to detect hypoglycaemia during the night or day
- Pregnant ladies with diabetes, gestational diabetes or trying to conceive
- People with diabetes wishing to reduce erratic blood glucose fluctuations
- People with diabetes who are involved in sporting activities
- People with diabetes whose concentration is affected by changing glucose levels
- People with diabetes who require additional monitoring whilst driving
- People with diabetes who live alone
- People who are changing diabetes therapy such as starting insulin pump therapy
- People with diabetes who require observation during hospital admission
Facts about Continuous Glucose Monitoring (CGM)
With the availability of continuous glucose monitoring devices, we have entered a new millennium in diabetes care. Glucose monitoring up to the 1980s was done in urine, and during the last 30 years we have become used to ‘spot testing’ glucose in the blood. It has become evident that continuous can be measured continuously in the tissue fluid via a subcutaneously inserted sensor. While you go about your daily activities, continuous glucose monitoring (CGM) “reads” your glucose levels throughout the day and night. It gives you a window into the patterns of blood glucose highs and lows after eating different foods, physical activity and insulin bolusing, and allows you to gain better control.
Benefits of CGM
- Can tell if blood glucose is rising or falling, indicating a possible need to treat
- An alarm sounds if blood glucose goes too high or too low
- Can improve diabetes control with a lower risk of hypos
- Assists in adjusting basal insulin and meal bolusing
- Invaluable for very active people and athletes requiring insulin
Limitations of CGM
- Does not yet replace the fingertip blood glucose testing: you still need to do a BG meter reading for accuracy & conversion of electrical current (Amps) into mg/dL
- Information overload: requires expert training and competence in diabetes & insulin management
- Expensive: Not always covered by insurance companies
Learning Curve in CGM
The CGM sensor is an ultra-thin flexible electrode you insert under the skin, which transmits tissue glucose measurements to the receiver, where they are displayed in real time. You need to replace the sensor every five to seven (3 – 7) days (depending on the make of the CGM) although in practice, many users are finding that a sensor can be safely used over several spells of the minimum durability indicated. You will also need to learn to align the sensor tissue fluid glucose level to the blood glucose readings you get from your BG meter and understand the “lag” time difference between their readings at the time of rapid change, such as up to two hours post-meal or with an approaching low.
Three subcutaneous enzymatic sensors in four systems are currently available. They differ in needle length, sensor wear, number of calibrations and time from placement to display (The Continuous Glucose Monitoring System (CGMS) by Medtronic-Minimed (Northridge, Calif., USA), was the first system approved by the FDA. The sensor is introduced through the skin and connected to a portable pager-size monitoring unit that records the sensor signal for several days. The monitor records the signal from the sensor every 10 s, then uses these readings to calculate and store the average value every 5 min. Data are downloaded onto a computer and are presented as a continuous glucose level. The sensor signal must be calibrated against capillary blood glucose at least 3 times/day to match up correctly with blood glucose levels.