CGM Unit

Hello all from Va,
Just got my CGM unit and was wanting to get any hints, tips or tricks that goes along with this unit. Any advise would be great!!

Errrrrrrr...which unit do you have...;-)

Sorry have the Medtronic Minilink Real time unit!!

From my use of the same sensor, I've learned the following:

  • Never use the CGM reading instead of a meter for adjusting insulin.
  • Only use pre-meal BG tests for calibrating - the more stable the BG, the more accurate your CGM readings will be.
  • Your meter and CGM will almost never agree - the CGM has around a 30 minute delay from what your meter will show. In fact, if you use a couple of different meters to check the same drop of blood only rarely will the numbers be the same - the same applies with a CGM. Some people get frustrated when the readings are inaccurate.
  • Being well hydrated seems to make my CGM reading more accurate.
  • The CGM is good for seeing trends and for early warnings of lows - especially if you sometimes don't get overt symptoms. Use it with that in mind.
  • Avoid the temptation to adjust your low BG alarm up too low if the alarms get annoying - it could cause you to miss an oncoming low until it is too late.

Used properly and with realistic expectations, the CGM is a great tool and the data it produces can be truly illuminating.


When inserting, try a deeper insertion angle. I find I only have to go slightly deeper (about 50 degree angle) but sometimes an even deeper angle can be beneficial. It can also help to place two fingers on either side of the sen-serter's 'feet' and pull the skin taught slightly. When I insert on my upper abdomen, I sometimes have to go at a shallower degree, about 35.
The sensor can be inserted pretty much anywhere you'd put an insertion set. Arms, legs, abdomen, hips - just remember to adjust the insertion angle as necessary.
If the sensor isn't in all the way after using the sen-serter, you can finish pushing it in manually. I find that pinching the skin or alternately pulling it taught helps.
To help prevent excessive bleeding, leave the introducer needle in for a few minutes after insertion. If the site bleeds after you've pulled the needle out, put a tissue over the sensor (where the needle was) and apply light pressure.
You can hook a transmitter up to a bleeding site, after doing the above. In fact, many of us have noticed that a site that continually or occasionally bleeds throughout the sensor life is a Very Good Thing.

After insertion, a lot of people wait to initialize the sensor in order to allow for "wetting". For people who find that the first several hours of their sensor life is not as accurate as it might be, this can be an extremely helpful practice (I do not do this). It is common practice to insert the sensor at night and initialize it the following morning.


From day one I've known that taping the sensor/transmitter down extremely well is one of the most important factors for success. The more stable your sensor, the more stable your readings.
Opsite Flexifix. I can't recommend it enough.
Some people place a strip of paper tape over the sensor prior to placing an adhesive coverage (like Opsite) over the whole works - the theory being that paper tape will absorb any excess moisture that may collect under the adhesive. (I've personally never tried this)

If you're new to this system, it's not a bad idea to calibrate only when your BG's are absolutely stable. No arrows on the graph screen, and never during a hypo/hyper episode. Minimed now recommends that users do no more than 3 calibrations / day - I believe that it's not the quantity, it's the quality. I average about five calibrations per day successfully. You have to find what works for you.

Base post-meal calibrations on your active insulin time. If that time is four hours, don't do a postprandial calibration two hours after a meal; instead, wait four.
For preprandial (before meal) calibrations, wait at least fifteen minutes to eat after calibrating so that the system has time to accept your calibration without any subsequent fluctuations.
I calibrate successfully during fluctuations; however, only if there is one arrow on my graph screen (showing a slower rate of change) and only if my BG isn't a high high or a low low (i.e. over 12 and under 3.0).

Restarting a Sensor
By far, the most common question I see regarding the RT system is how long the sensors can be used for. The longest I've gone is three weeks; we had another member, Drea, who wore one for a month. YMMV applies, of course. To coax your sensor past three days:

At the first "Sensor End" message, 72 hours after you plugged the Minilink into the Sensor, restart the sensor by going into the Sensor menu on your pump and selecting "Sensor Start" and then "New Sensor". The pump will ask you for a BG calibration about five to fifteen minutes after this, preventing the two hour initialization time.
On day six, the Minilink must be disconnected from the sensor and recharged in order to reset the timer. Leave the old sensor in, let the Minilink charge up (about twenty minutes) and reconnect it to the old sensor. Tape it up again (remember, tape tape tape!) and use the "Sensor Start" --> "New Sensor" options to reinitialize the sensor. This will result in the two hour initialization time.
After another 72 hours, start back at step one by simply telling the pump that you've inserted a new sensor. Rinse, lather and repeat!

There are many informative discussions here on Insulin Pump Forums about the ISIG value and it's importance to the success of a sensor. Rather than repeating all of that, I'll simply say that the most important things I look for in my ISIG value are:

I know my sensor is doing well if my ISIG value is at least 1.5 times the value of my BG. NOTE: my BG is registered in mmol/L
If my ISIG value drops below my manual BG value in the first three (or so) days of a new sensor, it isn't a big deal; I just don't calibrate until the ISIG rises to at least equal my BG. If the ISIG is below after day three, it is a good indication that the sensor needs to be pulled.
ISIG values over 200 (on the pump or with the test transmitter) are a pretty good indication that the transmitter is dying.

Never just pull a sensor without trying at least a few restarts - sometimes it's a guaranteed fix-all.

This was first posted on by Tiffany