Diabetic Dopers- Glucose Monitor on Crack, Now What?

So, I’ve been hypoglycemic my whole life. Except now, 2/3 of the way through pregnancy, when I appear to have gestational diabetes. Grrrr. So, my doctor tells me to test my blood sugar more regularly, and keep it below 120.

Ok, cool. Well, I had just moved, and couldn’t find my regular monitor. My insurance is happy to spring for a new one, so I get a fancy-pants Accu-check Active. Life carries on.

Yesterday I find my old monitor, a Prestige IQ. Yay! Tonight, for shits and grins, I test myself on both at the same time. The results? 20 points different! The difference between good and very bad BS.

I run control solution checks on both monitors. Both monitors check out just fine. I call Accu-chek Tech Support. They have no advice to offer.

So now what? Which do I believe? Prestige (lower) or Accu-chek (higher)? My “old” monitor is only 3 months old, so it isn’t exactly really old yet.

Is there any way to know which monitor is correct? 20 points is quite a lot. Anyone ever seen such a thing before? Why are my glucose monitors on crack?


Unfortunately, no. Those meters can often be off target.

I’ve been an insulin dependent diabetic for a few years now. Once, I could feel a low blood sugar coming on and so I tested it. It came out 120. I knew that was wrong and tested it again, this time it came out 73.

You best bet would be to test on both machines again and see if this time they were more compatable.

Monitors can mess up some are more flakey then others.

I once used Reli-On (wal mart brand cheapest there is) it said I was 130 when I felt like I was about to keel over. I tested again with my more expensive monitor and I was 55.

Even if all of your monitors are a decent there is a rather large margin of error (how you handled the strips, if the monitor had recently been too hot or too cold, battery power, any oils on the skin that mixed with your blood etc etc) so if you ‘feel’ different from what they are telling you you should always re-check.

Yes. Go to your doctor, have a blood work-up for glucose, and do a meter check at the same time. Compare the results. Should give you a good idea.

I once talked to an Australian PhD who evaluated glucose meters. He said they were often way off, but better than nothing at that point. Having run thousands of glucose tests on lab instruments (and a few meters), I can tell you that even the best machines will show a 5% (or less) variation in sequential readings from the same sample. It’s called random error, and one of the few things that will make a Dr. go from zero to full hissy fit in 20 seconds. POC meters are worse in random error, perhaps up to 20%. I know it’s expensive, but repeat testing may give a more accurate answer. In the lab, retesting was a reflex action for me.

The two meters you have may also use different testing methods (i.e. chemistry) or pad reading methods that will introduce bias; one meter will always read higher than the other because of differences in design and operation. Another thing to keep in mind is that you are a dynamic system: your glucose won’t be the same 30 minutes from now because your body is doing something to it. You could try testing on a new sample in 45-60 minutes from the first test to see which way your sugar is going, and take action based on the direction and amount of change.

Urine glucose strips can also provide another data point. Glucose is filtered out of the blood into the kidneys, and then back into the blood before the blood leaves the kidneys completely. Below 140 g/dL, all of the glucose is returned to the blood. Above 140 g/dL, not all of the glucose can’t be returned to the blood, and the excess is carried out in urine. Note that a normal person can have a glucose spike (thus glucose in the urine) if they eat a high carb meal or snack. If you have glucose in your urine four hours after a meal, you may have a problem.