Differing Blood Sugars within a minute or so

Nothing unusual there. Personally, I would count it as 5.4, having averaged the 2 most likely. All meters throw out rogue readings sometimes, and I suggest that is what the 3.6 was. Meters are only accurate to within plus or minus 15%, and strips can easily become contaminated - as can your fingers. You did the right thing to re-check that 3.6.

redrickshaw said:

How can i trust it now?

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I think I right in saying the blood test shows you where you were 15 mins ago, sure I read that some were.

That being said its is only snapshot of what's going on and if you get 2 numbers almost identical it would be safe to assume they are most likely to be the accurate reading, there is always a small margin of error in the equipment nothing to worry about, its accurate enough for our purposes. (if that's what your asking which number to trust)

Literally anything you eat will cause a rise in bg readings because that's what happens when food is digested, the thing your trying to avoid is big rises "spikes" and looking at your readings that does not seem to be happening.

There is no Spoon said:

I think I right in saying the blood test shows you where you were 15 mins ago, sure I read that some were

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This is true when you are measuring interstitial fluids with a Libre or CGM.
A finger prick measures your bg now because it measures blood.

There is no Spoon said:

I think I right in saying the blood test shows you where you were 15 mins ago...

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Oh Helen beat me too it! I was about to say the same!

redrickshaw said:

Taking BS 2hr after eating 2 poached eggs, cooked spinach and a little gruyere. Machine said 3.6mmols - so I did it again 5.5mmols and just to check 5.3mmols. Hmmmm. Different fingers. I have a SD Codefree machine. How can i trust it now?

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The way meters work is that there's an enzyme, glucose oxidase, in the strip, which oxidizes or breaks down glucose into other chemicals, (hydrogen peroxide and d-glucono 1.5 lactone if you're looking for an answer which is bound to turn up in a pub quiz one of these days....) a few other reactions happen, this gives off electrons, more of them the higher the glucose is, which is measured as a current and translated into a bg reading.

There's a lot going on there - much more than just physically weighing an object - so there's a lot to go wrong, so it's almost inevitable that there'll be fliers.

But it's the best we've got, and we just need to be aware that if there's a reading which doesn't make sense, it's worthwhile doing a cross check.

Also, although I've never been able to find any papers on it, I'm not convinced that glucose is evenly, homogenously distributed throughout our incredibly complex bloodstream plumbing system. Arteries, arterioles, capillaries, lots of them, each subject to lots of biological factors in it's own area, it would be a surprise if bg in one area was the same as bg in another.

Scott-C said:

this gives off electrons, more of them the higher the glucose is, which is measured as a current and translated into a bg reading.

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Hi @Scott-C can I pick your brain on this one.

How do electrolytes effect this? i.e if you are taking supplements or drinking sports water?
About the only thing I know is the frequent need to pee, causes a loss of electrolytes, if the bg meter is reading current then the assumption would be due to a high bg which = loss of electrolytes, it would track as a low response, small current.

Assumption: increased electrolytes would increase the current and thus a higher reading, is that correct?
When reading bg as a current is this translated inversely to give a high mmol reading?

cheers.

There is no Spoon said:

Hi @Scott-C can I pick your brain on this one.

How do electrolytes effect this? i.e if you are taking supplements or drinking sports water?
About the only thing I know is the frequent need to pee, causes a loss of electrolytes, if the bg meter is reading current then the assumption would be due to a high bg which = loss of electrolytes, it would track as a low response, small current.

Assumption: increased electrolytes would increase the current and thus a higher reading, is that correct?
When reading bg as a current is this translated inversely to give a high mmol reading?

cheers.

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Ooh, I’d not thought of that. I’m taking potassium, sodium and magnesium supplements...

Scott-C said:

Also, although I've never been able to find any papers on it, I'm not convinced that glucose is evenly, homogenously distributed throughout our incredibly complex bloodstream plumbing system. Arteries, arterioles, capillaries, lots of them, each subject to lots of biological factors in it's own area, it would be a surprise if bg in one area was the same as bg in another.

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Absolutely.
There are backwaters, and different depths of channel, bends, kinks and narrow points.
Liquid simply doesn't flow uniformly though a system made up of so many different pipe diameters.

redrickshaw said:

Taking BS 2hr after eating 2 poached eggs, cooked spinach and a little gruyere. Machine said 3.6mmols - so I did it again 5.5mmols and just to check 5.3mmols. Hmmmm. Different fingers. I have a SD Codefree machine. How can i trust it now?

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If the figure dun seem normal for what u have eaten, test again. If the next two readings were close, the two closer ones are likely to be the accurate ones. If u have three readings that are apart but not ridiculously far apart, take the ave.