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sticking two fingers

pleinster

Well-Known Member
Messages
1,631
Location
Scotland
Type of diabetes
Type 2
Treatment type
Diet only
Dislikes
ignorance
Hi. I know that meters have margin errors, and I know that a million and one factors contribute to each reading, and I also know that this happens..and I have even referred to it myself as nothing to worry about...BUT...I'm interested in why people think stabbing one (clean) finger can produce one reading on a pretty reliable meter (with clean strips) and the stabbing another finger on the other hand seconds later can produce a reading that's 0.8mmols lower. I think it's to do with a conjunction between Mars and Uranus..but seriously would like some views.
 
Hi @pleinster ..
I have two meters .. TEE2 and SD Codefree .. which I alternate for comparative purposes .. and I have never found a difference of more than 0.2 mmol between them. I test 3 - 5 times a day .. fasting, pre and post-meal .. using different fingers on different hands. I am fortunate in that my BG seems fairly stable .. highest 6.2 and lowest 4.3 over the last three months .. and even though I have had the odd little wobble in my LCHF lifestyle, I don't think that I have ever had what could be called a spike.

I keep records of all my tests on a simple spreadsheet and I translate these readings on to graphs over each month. This gives me a clear picture of averages and trends over time which, I believe, are far more important measures than any difference(s) between individual readings. Recorded in this way, averages and trends over a 3 month period can be calculated and used as predictors for HbA1c levels between quarterly reviews.

I also think that if all of us T2s start doubting the accuracy or validity of meters as a whole, all that we will achieve (apart from driving ourselves daft with worry) is yet another "reason" for our Docs and Nursies to tell us not to bother testing
 
I'm having a bit of trouble with my meter, where testing the same prick has given me results from 6.0 to 8.1. When I get these results I just go back to the basics.
- choose finger and desinfect or wash it.
- let it air dry
- prick and dry off first drop
- I don't press next to the prick, but push another finger upwards along the pricked one.
- without touching the skin, I introduce the blood to the band.

Then it usually gives the same result.
 

Why would you take readings from Mars and then your anus?
However, most doctors assume and instruct patients to use their monitors to take individual readings because to give them an idea what their blood sugar is at that moment in time. If you are driving taking an individual reading before doing so makes sense. If you feel a hypo on it's way, you test to see if you need to take action.
It a monitor is more useful as has been said is over time to see how you trending and if your tolerance to certain foods is getting better or worse.
 

Hi. You may have misunderstood my post. I am not doubting the relative accuracy of my meter. I have used the same one for two years now and I know it is very slightly higher than some others..and that suits me. I have also kept very detailed records in the past from readings to food eaten (including breakdowns in terms of nutrients in a weekly diet) to meds taken. My spikes were generally all due to a steroid I had to take (the one that caused my diabetes in the first place). My question was entirely genuine...I wanted to see what other reasons people might come up with. You may not have had more than 0.2mmols of a difference in readings taken seconds apart but I certainly have.
 

Thanks for the reply. Yes, I do know all that...what I am asking is, taking into account the margin of error in a meter (which I fully understand), why would two readings taken from two different fingers seconds apart differ by almost a whole mmol? I am only asking for people's views.
 
Hi @pleinster ..
I did understand your post (I think) and I do understand that you are concerned / bemused / unsure (insert your own adjective here) as to the 0.8 mmol difference that you have seen in your readings. My point is simply that I don't see this as particularly relevant in the overall scheme of testing several times a day and mapping against foods and meds over a period of several months, using a meter with which you are generally happy. But that's just my opinion .. not a criticism of your quest for other folk's experiences and thoughts about this issue
Hope this clarifies
 
Don't know the answer but I've sometimes wondered just how evenly or homogenously glucose concentrations are distributed over such a vastly complex plumbing system as the bloodstream. For example, if you were to pour several litres of black dye into a watertank in a big house, would you ever get the same concentration of dye coming out of each tap in the house? Haven't been able to find any papers on the subject ( blood, not dye!). Are some bits if blood just more "glucosey" than others because it's not been evenly distributed?


Also, it's maybe just that meters aren't measuring the glucose directly - they're inferring the amount from the number of electrons coming off from the breakdown by glucose oxidase, and there seems to he plenty of scope for error in such a flighty and transient thing as an electric current.
 
Ok heres my take on it:

As Scott-c has already alluded to, the bodies blood circulatory system is complicated to start with. If you imagine injecting some 'die' into one of the main large blood vessels it isn't instantly going to be dispersed evenly through out the entire body, and probably not completely EVER, now add in that the other cells in the body need to take up that 'die' at different times and in different quantities/rates, you can maybe see why one particular drop of blood could be different from the next drop?

Add in the variability of strips, meter tolerances etc (and the alignment of the planets!) 0.8 isn't that much different especially if your BG is towards the higher end of normal

As I say, my take on it, which from the planet I'm standing on at the moment makes sense! (to me)
 
Apart from the inherent inaccuracy of the way the meters work there is likely to be a different amount of interstitial fluid mixed in with the blood sample from two fingers.
 
I think that the authoritative answer on the mean accuracy of the meter is compating the average fasting BG readings in a period near a fasting BG reading made in alb on blood sample. If the values are way off I could suppose something wrong of the meter or measuring method.

The other thing could be some accidental error due interstitlal fluid or moisture or dirt.
 
If you consider the current ISO standard for accuracy, then each reading should be accurate to 0.8 mmol/l. which means that two meters OR two consecutive readings can differ by up to 1.6 mmol/l and still meet the standard so would have to be considered 'accurate'. I use a SD Codefree and find this meter consistently reads between 1 and 2 mmo/l higher than any other meter I parallel test against it. My Freestyle Xceeds and my NEO used to be always averaging this amount when averaged over a couple of weeks, so I used to consider any difference greater than the 2 mmol/l as being indicative of a misread, and so force a retest.

Now my CCG has made me change to a Caresense Dual, which averages about 1 mmol/l lower than the SD, so has better correlation. But on a spot reading, I can still differ by about 2 mmol/l between the two meters, even off the same drop of blood, so I rely more on averaged results than spot readings.

There are many things that can affect readings that may also vary between test sites at any given moment. The blood haematocrit value will shift the readings, so can introduce extra error. Many meters are sensitive to maltose and similar sugar alcohols, so what you ate and when may also be skewing a result. The glucose level varies quite considerably following a meal, depending on GI and this introduces a dynamic quality to the Quantity which will not be in synch across the hands,

For hardened diabetics, then peripheral neuropathy may be affecting the blood flow in each hand, as may arthritis and plaque distribution/ constriction. Similarly temperature may affect blood flow differentially.

Just a few thoughts on the topic, probably irrelevant, but things that can affect readings over and above just glucose concentration.
 
I've always believed that differences in readings between fingers (or from the same finger at slightly different times), is due to the fact that our blood and and the glucose in it is constantly circulating, and so the amounts of glucose at different times/points most likely won't be identical. Which may or may not be correct, but actually makes perfect sense to me...

Robbity
 
Thanks for the thoughts, people. I was beginning to think one finger was just lying to me.
 
pleinster said:
Thanks for the thoughts, people. I was beginning to think one finger was just lying to me.
Click to expand...

I think it is giving you the finger for stabbing away at it for some time, mate!
 
Hi @pleinster . Can't really offer much on two finger prick testing, but did once perform a similar experiment with my toes.
First little piggy had been to market. BS reading 4.9 ( we think the walk dropped his sugars )
The next little piggy stayed at home. BS reading 5.7 ( to be expected )
Next little piggy had roast beef. BS reading 7.2 ( to much protein ?? )
Next little piggy had no roast beef apparently. BS reading 8.3 ( liver dump maybe )
Last little piggy went wee wee wee, well at this point we realised he was diabetic and we had some insulin .
So sorry for this post but there's nothing on the telly.
 
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