Comparing Meter Readings on Your Diabetic Dog

I can’t tell you how often I see side by side pictures of two hand held meters and the numbers aren’t the same. That makes people untrusting of both meters. Today we will discuss why the readings aren’t identical or seemingly even in the same “ballpark”. One piece of advice….don‘t do it unless of course you want to make yourself insane. We have discussed hand held meters in the past  here.

The key to any hand held meter be it a human meter or a pet meter is that they have to be within 20% (plus or minus) of lab equipment, in our case, most often an IDEXX machine. I see all the time where a person takes their meter to the vet’s office to see if it is close to the vet’s meter and the numbers are pretty far apart so the vet says, “That meter is junk, don’t use it”. Well, let’s take a step back and understand what is going on in that case.

Given that each of those meters has a +/- 20% allowable variance, as long as those two numbers are within 40% of each other, they are both doing their jobs! That’s a pretty big deal! If you are going to take your meter to the vet to test its viability, then it must be tested against a blood draw and IDEXX reading -- not another hand held meter. If you are doing the same thing at home, comparing two hand held meters, prepare to see two numbers that are significantly far apart in many cases. This is a recipe for making yourself crazy!

What do I mean by a 20% allowable variance? Let’s say that you do a BG (Blood Glucose) test and the reading for simplicity sake is 100. According to the allowable variance, that number could actually be 80 or 120 or any number in that range if it was tested on an IDEXX machine. If you do a test and the number on the meter says 200, the actual number could be between 160 and 240 (20% of 200 is 40 points). If your test says 300, the actual number could be between 240 and 360 (20% of 300 is 60 points). The higher the number, the wider the allowable variance is. Let’s look at it another way

So you see, the higher the reading is, the wider the allowable range is. This is why you need to pick a meter and stick with it. Don’t take two readings with two different meters and expect to see them be very close. That’s not to say that they can’t be fairly close, I’m just saying that they are “allowed” to be different.

Other factors when comparing two different meters are location on the body the reading was taken. You can’t compare an “inside of the upper lip” reading to a tail reading and expect to be spot on. Glucose distribution in the body is different so if you are verifying a wonky reading or against all advice comparing two readings, you must test at the same location on the body. You will also need to use the same blood drop keeping in mind that as soon as the blood hits the air, it begins to oxidize so your second reading can be a little bit off from your first from the same blood drop.

Because of the allowable variance of the hand held meters, we suggest that you follow trends instead of the exact number that you see (unless of course it is a low number). By that I mean if you are seeing numbers trending upward over the course of a few days or a week, it is worth looking into to find the cause. If your numbers are fluctuating from day to day by say 100 points, it is not worth getting upset over because depending on how high the reading is, they may all be in the same ballpark.

The moral of this story is to choose a meter and stick with that one. Periodically check the running average that all meters have. I believe that they still track the 7 day running average, the 14 day running average and the 21 day running average. By checking all three of the averages, you will see if your numbers are trending up or if they are trending down. Have a look at those averages and see how you’re doing and try not to freak out every day if your numbers aren’t exactly the same.

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Until next time…