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On Sat, 14 Apr 2007 18:08:32 -0600, "TigerLily" <me@privacy.net>
wrote:

G'day G'day Kate,

 Vitamin C did give false readings on the strips that used reducing
power as the indicator of blood glucose. These strips weren't
selective.  They worked on the assumption that the only common
reducing agent that could be present in large quantities in the blood
was glucose.  Then along came the mega dosing folks with their 1000 mg
tablets of Vit C. For the first time there was another reducing agent
present in sufficient quantity to affect the readings.  While some
other drugs also had reducing properties they weren't likely to be
present in sufficient quantities to create an error worth considering.
(It is possible I've over looked some rarer one)  

Some other sugars besides glucose also could give false readings IF we
considered only glucose as being harmful.  However the other sugars
that could also act as reducing agents also glycated proteins and did
damage so it didn't much matter whether or not they were glucose. We
simply had to think of the test as a blood sugar test rather than a
blood glucose test.  Many of these sugars don't make it past the liver
so the problem sort of solved itself anyway.

OK, so what is the key point that needs to be made here?

Well at about the same time the electrical conduction based meters
came into production a more selective method of measuring the glucose
content became available.  (Someone with a better sense of history is
welcome to correct my time scale.)  Enzymes are amazing.  Truly
amazing.

In the tertiary institute library where I work there was a diagram of
an enzyme showing the specifics of a lock and key model for an enzyme.
The substrate (chemical to be reacted, in this instance glucose) had
to fit into the cavity in the enzyme so that each functional group eg
OH had to fit in exactly the right place. It was like looking at a six
tumbler lock. The notches on the key had to fit perfectly or the
enzyme would not work.  

Some creationist student had scrawled in the book, "So now do you
believe in God?"   I smiled.  They had a point.  It takes a lot of
faith to think such a precise system as that required by enzymes to
work could have evolved.

Sorry about the ramble.  My point is the electrical resistance meters
as I have experienced them are LESS likely to be influenced by Vit C
since they use enzymes which are highly specific.

In the end it is probably no big deal.

Best wishes,