Caution for sensor users

I have found the freestyle libre sensors very helpful but want to issue a caution about them. My vet told me the sensor reading and handheld meter reading could be different. Sure enough for my own cat i consistently see the sensor up to 100 points lower. However i am told that individual cats vary and the sensor could be higher for some. The diff for me is greater at higher numbers. So cross check your readings!

 

Here is comparison I did with my Badger's sensor and my human meter. Not that over time it switched which (sensor or meter) read higher

 

Depends on what type of handheld meter you use also. Pet meters like the Alphatrak read higher than the human meters. The Libre Freestyle CGM (continuous glucose monitor) is more like a human meter. Similar, but not the same.

Human meters (hand held meters, glucometers) can vary from 1 test to the next as the FDA allows some variance in the readings and still considers them "accurate enough." The Libre is in essence a human meter, simply attached differently and reading the interstitial fluid glucose levels instead of the blood glucose levels.

Human and pet meters read differently at different number ranges also. Closer together at the lower BG ranges, higher at the higher BG levels.

It's why we have our color coded standardized spreadsheet. Ranges are on there. The ones I have stated below are for the human meter. We have separate templates for pet vs human meters.

Black is too darn HI(>500), Red (400-499) is way too high also, pink (300-399) a bit better but still a lot of room for improvement, yellow (200-299 ) getting some control back but could be better. Blue (100-199 ), now your talking! Insulin dose getting better. Green (50-99 ) excellent! Gives the pancreas time to heal. Bright green (<50)
- WATCH out, HEADS UP! Kitty is headed for hypoglycemic (HYPO) territory and you need to monitor and maybe bring those BG numbers back up. "Feed the curve."

It's one reason we don't focus too hard on the specific BG readings for any test, but instead see where the BG levels fall within a range. And look for waves of patterns on the SS.

Depends on which insulin you are using also AND what time in the 12 hour dosing cycle you are seeing the specific BG readings. Also depends on how much data you have gathered to know YOUR cat's onset, nadir, duration with the specific insulin you are using. It's not as simple as saying BG of 400, or BG of 90 is good or bad. When the BG tests are obtained and what insulin you are using are as important if not more so than the BG reading.

Bouncing, fur shot, skipped shot, how much your cat ate, played, chased the other cat around the house, etc, etc can all cause variations in the blood glucose (BG) levels.

It's all has to be put into context.

Like comparing apples to oranges sometimes. Yes, they are both fruit. But not many people would mistake one for the other.

ECID Every Cat is Different, Every Caregiver is Different, Every Cycle is Different.

 

I used the Freestyle Libre for 2 weeks and found the numbers between the sensor and the handheld glucometer were much closer in readings when the numbers were lower (like in the 50-99 range). Most of the time, the sensor wasn't that helpful except it did show me if glucose levels were rising or dropping.

 

The freestyle continuous reader uses ISF and not blood to give you readings. Interstitial fluid surrounds blood cells, so there is a lag in the actual blood glucose readings causing it to be a bit lower since the sugar registers inside the cell first. This is also why those tiny, thinner looking BG samples people squeeze out of the ears after repeated pokes are also problematic since that can also be ISF and not blood. It looks like watered down blood samples....
So, it's almost like pre-reading before the spikes and rises that happen over the course of a cycle. It is more helpful to view trends than specific spot checks. Since it tells you how low your cat could be or was, I still think it could be helpful in that way overall.

this post explains it pretty well.
https://www.medtronicdiabetes.com/c...y-sensor-glucose-does-not-equal-blood-glucose

 

What’s the difference between a sensor and a handheld? Aren’t all the Meyers handheld? I have Freestyle do just wondering. Thanks!

 

The sensor for Freestyle is called the Freestyle Libre. It is implanted on the cat (only stays for 2 weeks) and you pass your iPhone with an app or the reader over it to get the reading. No pokes.

 

Very interesting thanks