Type 2 Confusing readings

Hi Plantagenet, yes there can be quite a bit of discrepancy between various meters, the best way to double check them is to ask the manufacturer for their control liquid,this is a liquick that gives a known result ,from thier you can see how much " out" the machines are, not so easy but it does give you a better reading for your meter ( and confidence in your bs testing) clive

Good advice from Clive, many blood/glucose meters can vary by up to + or - 15% and still claim to be accurate and comply with the ISO standard.
Also it's worth remembering that some of the older blood/glucose testing meters have dual standard displays in that apart from displaying the result in mmo/L (UK preference) they can also display the results in mmol;/DL. (US preference) If that wasn't bad enough the meter that I personally use can also display results in 'FULL BLOOD' as well as the estimated equivalent 'PLASMA BLOOD' readings, which would mean that testing the same blood sample can result in 4 apparently differing readings.
It's worth checking if your meter is one of these older models that has programmable settings options that cover all of these options and if you live here within the UK then it should be set to mmol/L and 'Plasma' so as to comply with the greater majority of reference that you will see here on the Diabetes UK website..
As for the changes in readings over a short time period, well this is normal, Blood Glucose levels are known to change by the minute and it's also worth remembering to discard the first Blood Droplet after lancing the finger and obtain a second droplet as errors are know to be worsened by testing on the first droplet of blood that may have been static below the surface of the skin. The second droplet reduces this error considerably, though most meter manufacturer's fail to mention this in their instruction booklets.

Lazybones said:

discard the first Blood Droplet after lancing the finger and obtain a second droplet as errors are know to be worsened by testing on the first droplet of blood that may have been static below the surface of the skin. The second droplet reduces this error considerably, though most meter manufacturer's fail to mention this in their instruction booklets.

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I never knew anything of this.Is it a fact? thanks for the info Lazybones

Errors of 0.4 and 0.5 mmol/L are well within the specified accuracy of most meters.

What were your actual readings?

plantagenet said:

Is there any point in testing any more?.

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Well that depends upon whether you'd like to know your BGL to within about +/- 1 mmol/L (or 15% for higher readings) or if you'd rather have absolutely no clue at all? It's your call.

BTW. That's the accuracy spec for my meter. Some might be a little worse than this (eg +/- 20%).

Dear Numan43,
Yes it is a fact but unfortunately it's one that most diabetics aren't aware of or have been told about. The trend in recent years has been to produce meters that use an ever decreasing sample size and any error in testing such small samples is as a consequence greatly magnified.
The first droplet may well have rested there just below the skin's surface and hardly moved and having lost it's surrounding glucose through cell take up will as a consequence give a slightly lower and false reading - For this reason a second droplet will usually prevent this error occurring.
Hope the info is useful to you all. - Best wishes - Lazybones

plantagenet said:

Obviously I'm expecting too much, but I think that level of (in)accuracy is appalling. That means if someone got a reading of 12 mmol/L, it could actually be 9.6 mmol/L, or worse, 15mmol/L

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Or between 10 to 13.8 mmol/L for the better 15% spec.

Yes it sounds like you were expecting a bit too much as far as accuracy goes. Remember that once upon a time we had no easy way of self testing at all. Sit and imagine what that must have been like for diabetics, and then be thankful that you have what you have.

Lazybones said:

Dear Numan43,
... The first droplet may well have rested there just below the skin;s surface and hardly moved and having lost it's surrounding glucose through cell take up will as a consequence give a slightly lower and false reading - For this reason a second droplet will usually prevent this error occurring.

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Didn't know this!

Is this why I think I may have also seen people rubbing the skin before taking blood?

plantagenet said:

Point taken.

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Yeah don't worry, you're not the first person to suddenly realize that our meters aren't quite as perfect as we often think they are.

I think the thing that most disappoints people when they learn this, is that it's often those little changes of +/-1 mmol/L or so that give us our own personal sense of a little victory or failure each day. Like if I wake up and test 5.5 when I normally test about 6.5 to 7.0, then I pat myself on the back and say: "yeah I was really good with my diet yesterday, and that walk last night really did the trick". It's kind of deflating to think that it might have been just a random error in the meter and nothing that I did.

One consolation though. The accuracy specs are meant to cover a range of climatic conditions and a range of other possible interfering factors and of course to cover the variance of the strips from one batch to the next. The reality is, that for a given batch of strips and testing at fairly stable temperature conditions etc, I usually get a lot tighter than +/-15% when I do consecutive readings.