Differences

[Deleted member 19555]

Can anyone tell me why I get two different readings from two different fingers - index and one next to it - even though both are treated the same beforehand with regards to cleanliness/hygiene, and the second one is taken immediately after the first. The index finger seemed a little high to me, so I took it on the next one and it went down by four!

 

[helli]

4mmol/l is a big difference? Do you mean 0.4 mmol/l difference?
Meters are not 100% accurate. It is often stated that there is a15% tolerance.
The absolute room for error is dependent on the actual reading. But let's take an example - if your blood sugar is really 6.5 mmol/l if it was tested on a complete accurate lab machine, the meters we have with the strips we use coud be anything between 5.5 and 7.5.

So, two tests taken from the same finger from the same "lance action" could be different.

 

[trophywench]

Plus of course, the veins in the ends of fingers are peripheral veins, not main ones. Venous blood drawn off by a phlebotomist, put in a vial and sent off to a lab for testing is drawn from a main vein.

 

[Deleted member 19555]

4mmol/l is a big difference? Do you mean 0.4 mmol/l difference?
Meters are not 100% accurate. It is often stated that there is a15% tolerance.
The absolute room for error is dependent on the actual reading. But let's take an example - if your blood sugar is really 6.5 mmol/l if it was tested on a complete accurate lab machine, the meters we have with the strips we use coud be anything between 5.5 and 7.5.

So, two tests taken from the same finger from the same "lance action" could be different.

As I said, its from two different fingers, not the same one.

 

[Deleted member 19555]

The short answer is no. If you took a reading from every finger one after the other you'd most likely get eight different readings. If I get a reading that I think is a little on the high or low side I switch hands and test again. If the results are close I'll shrug and use the average. If they're very different I'll do one more and average the two that are closest.

Incidentally the usual advice, including on this site, is to avoid using thumbs and index fingers for testing.

Well a lot of people use index finger, including on this site, and nobody told me otherwise at diabetes clinic so I have used this all along.

 

[helli]

As I said, its from two different fingers, not the same one.

Sorry, I was not clear in my response.
My point was that even if it was from the same finger, the readings could be different and, obviously, if the same jab from the same finger could be different that different jabs and different fingers could also be different.

Well a lot of people use index finger, including on this site, and nobody told me otherwise at diabetes clinic so I have used this all along.

I too have used my index finger for over 15 years and have never had any problems as long as I rotate my fingers and don't use the same ones all the time.

 

[Hepato-pancreato]

Take your blood pressure on right arm then left and you will get a different reading. Same as using your spare meter different reading.i was having ketamine infusions a few years ago, they lasted 6 hours every 1/2 hour they tested my bg's. Guess which finger they used? None they used my toes.....ha! Ha!

 

[trophywench]

Be different again in your toes as it's a lot further from the lovely bright red well oxygenated blood your heart pumps out. (assuming you don't have ape's arms and corgi's legs ....)

 

[everydayupsanddowns]

I don’t think it’s anything worth worrying about @Ditzyoldme

It could be differences in the blood (blood is not an entirely homogenous substance, and there will be differences in concentrations of various things in circulation at various places of the body.

It was most likely strip-to-strip variation though. Even small dofferences in the concentration of the reactive agent in the strip itself, plus the hand cleanliness/technique that you have already mentioned can give rise to variations in results, but by law these need to be less than 15% from a lab value 95% of the time, and closer than that at lower levels.

For all the illusion of decimal point accurscy, Bg meters are really providing more ‘ish’ information. Small differences can be ignored, and any reading that seems unusual or unexpected, or which doesn’t match how you feel should be rechecked 🙂

This chart shows the allowable variations - which can get to be quite wide!