Does fasting times effect the glucose results?

On 9 Nov 2003 15:35:39 -0800, [email hidden]

(Mikefbolen) said:

Recently had a blood test done, fasting glucose was 109. I did not eat since 7 that night, took the
blood test around 10 that morning, about 15 hour fast. If I would of fasted longer or shorter, say
11 or 8 hours would the fasting glucose number change. What I am thinking is since I fasted 15
hours instead of the 8 hours maybe my glucose true figure would be much higher than 109. Any
opinions on this? Mike

Once your liver had dumped all it has then when the BG level goes below whatever threshold you have
set in your system, the body starts processing other sources. Fat etc then it starts eating itself.

Pete

Diagnosed 20/03/03 Type II D&E + Metformin + Gliclazide
+ Asprin 210lbs at Dx to target 174lbs achieved. Now 171lbs. To mail: aspen3 at freeuk.com

"Mikefbolen" <[email hidden]> wrote in message
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Quoted message said:

Recently had a blood test done, fasting glucose was 109. I did not eat since 7 that night, took
the blood test around 10 that morning, about 15 hour fast. If I would of fasted longer or shorter,
say 11 or 8 hours would the fasting glucose number change. What I am

thinking

Quoted message said:

is since I fasted 15 hours instead of the 8 hours maybe my glucose true figure would be much
higher than 109.

Any opinions on this?

Well it would've been different at the 8 hour mark, and different again at the 4 hour mark (anytime
we're not eating we're fasting) so I suppose the "specialists" have decided on a 12 hour fast as
being the "benchmark" figure for that reason.

Beav

Mikefbolen said:

Recently had a blood test done, fasting glucose was 109. I did not eat since 7 that night, took
the blood test around 10 that morning, about 15 hour fast. If I would of fasted longer or shorter,
say 11 or 8 hours would the fasting glucose number change. What I am thinking is since I fasted 15
hours instead of the 8 hours maybe my glucose true figure would be much higher than 109.

Any opinions on this?

Mike

I think you have a good point there, although fasting longer may actually give you a higher
glucose reading, rather than a low one. There's the whole problem of the Dawn Phenomena. A
lot of people have told us in these newsgroups that their readings are higher in the morning
because the phenomenon, and that if they don't eat breakfast as soon as they get up, their
glucose levels continue rising until they do eat. I've seen it happen in myself.

Fasting 15 hours seems above and beyond the call of duty in this situation. I believe the
usual instructions are to fast only about eight hours. The other problem is lateness of the
hour they took the test. I can certainly understand having to get ready and drive halfway
across town to the laboratory, only to be told to cool your heels waiting room until the end
of ready to see you. It can easily be 10 o'clock A. M. the morning before that can happen,
but it would probably the better if you could get tested at the time you normally get up in
the morning and test yourself.

This won't impress your doctor, I'm sure, but it might give you some information for
personal use, if you tested yourself when you get up and then again time when the
medical lab draws your blood. That would give you some idea about how much, if any, your
glucose levels rise because of the delay in getting the medical lab test done. Then you
could subtract the difference from the medical laboratory's result and come up with your
actual reading.

Your reading of 109 looks pretty good.

E

There shouldn't be a difference in BG between an 8 hour or 11 hour fast. However, BG can be
different depending on what you did in the extra three hours. For example, if you eat at 9 pm, goto
to bed at 10 and wake at 6 am and do not eat, BG will be different at 6am then at 9am because you
been up for three hours, even if you don't exercise.

Al

"Mikefbolen" <[email hidden]> wrote in message
"]news:[email hidden]...

Quoted message said:

Recently had a blood test done, fasting glucose was 109. I did not eat since 7 that night, took
the blood test around 10 that morning, about 15 hour fast. If I would of fasted longer or shorter,
say 11 or 8 hours would the fasting glucose number change. What I am

thinking

Quoted message said:

is since I fasted 15 hours instead of the 8 hours maybe my glucose true figure would be much
higher than 109.

Any opinions on this?

Mike

"Mikefbolen" <[email hidden]> wrote in message
"]news:[email hidden]...

Quoted message said:

Recently had a blood test done, fasting glucose was 109. I did not eat since 7 that night, took
the blood test around 10 that morning, about 15 hour fast. If I would of fasted longer or shorter,
say 11 or 8 hours would the fasting glucose number change. What I am

thinking

Quoted message said:

is since I fasted 15 hours instead of the 8 hours maybe my glucose true figure would be much
higher than 109.

Any opinions on this?

If you have diabetes, then fasting for longer would likely cause higher BG due to a liver dump. If
you don't have diabetes, it wouldn't matter because your BG will never be too high.

--
Type 2 users.bestweb.net~jboveOpen ↗

"Mikefbolen" <[email hidden]> wrote in message
"]news:[email hidden]...

Quoted message said:

Recently had a blood test done, fasting glucose was 109. I did not eat since 7 that night, took
the blood test around 10 that morning, about 15 hour fast. If I would of fasted longer or shorter,
say 11 or 8 hours would the fasting glucose number change. What I am

thinking

Quoted message said:

is since I fasted 15 hours instead of the 8 hours maybe my glucose true figure would be much
higher than 109.

Any opinions on this?

Mike

It would not make a difference clinically. The 2 hr post meal glucose is more sensitive in
picking up glucose intolerance. The fasting glucose only becomes elevated long after, maybe years
before, after an abnormal 2 hr PP. becomes evident. If you want a heads up early detector then do
the 2 hr PP.

[email hidden] (Mikefbolen) wrote in
:"]news:[email hidden]:

Quoted message said:

Recently had a blood test done, fasting glucose was 109. I did not eat since 7 that night, took
the blood test around 10 that morning, about 15 hour fast. If I would of fasted longer or shorter,
say 11 or 8 hours would the fasting glucose number change. What I am thinking is since I fasted 15
hours instead of the 8 hours maybe my glucose true figure would be much higher than 109.

Any opinions on this?

Mike

Clinically, it makes no difference. An 8 hour fast really means a minimum of 8 hours. In practical
terms it means don't eat anything after you go to bed. Typically, people will eat dinner around 7
and then fast until their appointment. With an 8:00 appointment that is 13 hours, so 13 to 16 is
common. The diagnostic standards incorporate this variability.

In normal males, after the postprandial effects sort out, say a couple hours, blood glucose levels
fall at a constant, average slope of 0.2 mg/dl/hr for at least 72 hours. That means, assuming you
are normal, a difference of 1.5 mg/dl between the 8 hour and the 15 hour test values. Things are a
little more complex in women, but your name is, after all, Mike.

In diabetics, things are a little more confusing. Diabetics have defects in the hormonal signaling
system that controls blood glucose level and can be taking medication that has other effects.
Still, the difference between an 8 hour fast and a 15 hour fast would be expected to be in the
noise for most.

Charly Coughran [email hidden]

In article <[email hidden]>,

Beav said:

"Mikefbolen" <[email hidden]> wrote in message
"]news:[email hidden]...

Quoted message said:

Recently had a blood test done, fasting glucose was 109. I did not eat since 7 that night, took
the blood test around 10 that morning, about 15 hour fast. If I would of fasted longer or
shorter, say 11 or 8 hours would the fasting glucose number change. What I am

thinking

Quoted message said:

is since I fasted 15 hours instead of the 8 hours maybe my glucose true figure would be much
higher than 109.

Quoted message said:

Quoted message said:

Any opinions on this?

Quoted message said:

Well it would've been different at the 8 hour mark, and different again at the 4 hour mark (anytime
we're not eating we're fasting) so I suppose the "specialists" have decided on a 12 hour fast as
being the "benchmark" figure for that reason.

It depends on the person. My bg goes up after about 8 hours,

--
This address is for information only. I do not claim that these views are those of the Statistics
Department or of Purdue University. Herman Rubin, Department of Statistics, Purdue University
[email hidden] Phone: (765)494-6054 FAX: (765)494-0558

In misc.health.diabetes Charly Coughran ccoughran@delete_to_reply_ucsd.edu said:

In diabetics, things are a little more confusing. Diabetics have defects in the hormonal signaling
system that controls blood glucose level and can be taking medication that has other effects.
Still, the difference between an 8 hour fast and a 15 hour fast would be expected to be in the
noise for most.

That's assuming one totally disregards the likelihood of a liver dump.

Priscilla

Eldritch said:

told us in these newsgroups that their readings are higher in the morning because the phenomenon,
and that if they don't eat breakfast as soon as they get up, their glucose levels continue rising
until they do eat. I've seen it happen in myself.

If BG falls below 4 mmol/l glucagon will fire and signals degrading the glycogen stores in liver, so
BG will increase. The lesser it has been, the more glucagon will be released and the higher the BG
will rise. But after some time, BG start falling again, but not to the same level, so firing will be
less and the overshoot will be less next time.

You may find exactly the same phenomena in regulation of temperature in a room using both a cooler
and a heater operating in parallell. Some diabetes II will be an analogy to having them operating
at the same time, that is heater is heating the cooled air, thus increasing permanently the
temperature above the wanted level. (heater is the analogy of glucagon). What you then observe is a
kind of futile cycle where food energy is the loosing part, while in a room, your electric bill
will be the loosing part since it costs a lot to have both a cooler and a heater running,
especially if one the set points is far off wanted, like someone setting the heater on 40 deg C,
and the cooler at 18 deg C, with low range 16 deg and high range 20 deg, and heater at +- 2 deg
around 40 deg. Gives lots of fun :-)

My endocrinologist does not have me fast for a hba1c test. And from talking to the pathology people,
I know that is his normal practice with his patients.

Nev.

"Herman Rubin" <[email hidden]> wrote in message
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Quoted message said:

In article said:

"Mikefbolen" <[email hidden]> wrote in message
"]news:[email hidden]...

Quoted message said:

Recently had a blood test done, fasting glucose was 109. I did not eat since 7 that night, took
the blood test around 10 that morning, about 15 hour fast. If I would of fasted longer or
shorter, say 11 or 8 hours would the fasting glucose number change. What I am

thinking

Quoted message said:

is since I fasted 15 hours instead of the 8 hours maybe my glucose true figure would be much
higher than 109.

Quoted message said:

Quoted message said:

Any opinions on this?

Quoted message said:

Well it would've been different at the 8 hour mark, and different again

at

Quoted message said:

Quoted message said:

the 4 hour mark (anytime we're not eating we're fasting) so I suppose the "specialists" have
decided on a 12 hour fast as being the "benchmark"

figure

Quoted message said:

Quoted message said:

for that reason.

It depends on the person. My bg goes up after about 8 hours,

Mine would if I didn't use the right amount of background insulin. In fact it DID do, but not
anymore. The only time I get a spontaneous BG rise is between 8 and 10 in the morning, and not every
day. I know a few diabetics who would be floored at the 8 to 10 hours point after last eating too,
but they use FAR too much insulin (and they know it, but do it so they can eat like pigs:-)

Have you considered a tad more basal insulin Herm?

Beav

"Alf Christophersen" <[email hidden]> wrote in message
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Quoted message said:

Eldritch said:

told us in these newsgroups that their readings are higher in the morning because the phenomenon,
and that if they don't eat breakfast as soon as they get up, their glucose levels continue rising
until they do eat. I've seen it happen in myself.

If BG falls below 4 mmol/l glucagon will fire and signals degrading the glycogen stores in liver,
so BG will increase. The lesser it has been, the more glucagon will be released and the higher the
BG will rise. But after some time, BG start falling again, but not to the same level, so firing
will be less and the overshoot will be less next time.

Well, not exactly what I have been told.

When there is no (little?) insulin in my blood, glucagon will fire and release the stored glucogen
from the liver. Maybe this occurs around 4 mmol/l with normal people?

As long as I do not take any insulin, the BG will continue to rise. I may stop eating, but as long
as my insulin level is low the BG will rise. Also the dawn phenomenon will cause the BG to rise in
the morning to prepare my body for the next day.

--
Have a nice day Bjørn BL.

In article <[email hidden]>,

Nev. said:

My endocrinologist does not have me fast for a hba1c test. And from talking to the pathology
people, I know that is his normal practice with his patients.

This test does not test current bg levels, but a sort of weighted average for the preceding
few months.

--
This address is for information only. I do not claim that these views are those of the Statistics
Department or of Purdue University. Herman Rubin, Department of Statistics, Purdue University
[email hidden] Phone: (765)494-6054 FAX: (765)494-0558