Calibration questions

I just got a CGM and I really like it. But, the second time I put it in, many of my BG readings are up to 40 points different than my SG. For example, I had an SG reading of 76 and a meter reading of 56. In addition to that, there were no arrows next to the SG reading. I'm not sure what went wrong.

Part of the sensor was sticking out of my skin. Would this cause such a problem?

If you calibrate more than 4x a day, does it cause these types of results?

What type of CGMS do you have? And yes, if your sensor is not properly inserted, that can cause readings to be off. I have never used the Minimed one, but have heard people say if you calibrate too much, that makes things worse. I used the Navigator for awhile & just did a trial of the Dex and they didn’t have problems calibrating more.

As far as the no arrows, that can happen when your blood sugar is going one direction & fighting to go the other - the CGMS is basically confused about which way your BS is heading.

Is it a Minimed? I keep having the same problem…I’m going to try the Dexcom.

when i was originally trained on the minimed, i was told to calibrate at least twice, but no more than 4 time a day.
now they are training people to calibrate more frequently, at least 3-4 times a day (but only calibrate when the BG is level, not trending up or down)

You also have to take into account that your interstitial fluid levels can “lag” behind your BG levels. Also take into account that you are comparing 2 inaccurate numbers - the “acceptable” range for BG meters is plus-or-minus 20%; i don’t know what the “acceptable” range is for a CGM, but they are not as accurate.

kelly, what exactly do you mean by “bg is fighting to go in the other direction”? in someone with diabetes, the body can’t control the BG levels… kind of the defining factor of diabetes (both insipidus and mellitus)
Assuming we’re talking about a minimed, no arrows means that the CGM is unaware of any rapid change in glucose levels - on a minimed, a singe arrow means a rate of change of 1-2 MG/DL per minute, and 2 arrows means a rate of change of 2 or more MG/DL. (no arrows means a “stable” blood sugar.)

Minimed is currently telling people that a sensor will become inaccurate if the sensor is out of the skin by more than the width of a coin - there are 3 distinct sensor areas on the whole sensor, and all 3 need to be under the skin to get an accurate reading.

On both the Dex & Navigator, they have several directional arrows - straight up or down, slanted up or down (not going as fast) or straight across meaning you are staying stable.

Although someone’s body can’t control BG levels, if you ate something to cause your BS to go up and you also took insulin to offset your BS going up but there is a fight going on as to which way your BS should go, that is when the CGMS kind of gets confused as doesn’t have an arrow - at least on the Navigator & Dex. The one time I was talking to an upper-level customer service person at Abbott and I kind of joked about the arrows and said it is like it is confused, she said that is actually what is happening.

i’m … pretty sure that “insulin counteracting a rising blood sugar” results in a stable blood sugar. i’d have to double check with a medical professional, but it just doesn’t make sense to have a blood sugar going on both directions.

It is possible to have blood sugar going back & forth - I have already watched it on the Navigator. The Navigator reads every minute. I have triggered the alarms because of going up & down. In that case, your BS is not stable and the CGMS is not able to figure out which direction you are heading, hence it will not give you any directional arrow.

I believe that the navigator will not provide directional arrows if it loses communication at any time in the previous 15 minutes (since that’s where it gathers a portion of that trending information).
I don’t think it’s that it’s ‘confused’ by glucose going up and insulin trying to bring it down, especially since the interstitial glucose can be behind any type of “fight” that would be going on within the arterial system.
Regardless, it sounds like this is not a navigator problem at all ("…the sensor was sticking out of the skin…"). It sounds like MM. It has been too long since my experience w/ the MM to remember how the trending arrows were calculated and displayed, so I can’t really speak knowledgeably about what might be causing the “no arrow” to appear.

It is minimed. Does dexcom have a better CGM?

i trialed the dexcom, thought it was slightly better than the minimed, but i didn’t like carrying something else - i already have pump, meter, cell phone, and wallet (see my post above for more).

we use the minimed guardian. we calibrate about 5-8 times a day. we were told to calibrate with every other BG test. so we do.
i’d say that 90% of the time the meter reading and the finger poke reading is within 5-10 ‘points’ off. if his finger poke is 135 his cgm will most likely read 130 or 140.