PREGNANCY-BIRTH Messages for August, 2000: Re: 3 hour GTT (glucose tolerance test)for Dr. Montgomery and other medical personnel

Re: 3 hour GTT (glucose tolerance test)for Dr. Montgomery and other medical personnel

From: Lynn D. Montgomery, MD (anonymous@obgyn.net)
Wed, 30 Aug 2000 23:26:09 -0500 (CDT)

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In reply to: Ann: "Re: 3 hour GTT (glucose tolerance test)for Dr. Montgomery and other medical personnel"

At Wed, 30 Aug 2000, Ann wrote: >
>Thanks Dr. Montgomery and Tonja for your input! I had just happened to
>read a publication from the NIH re: these tests shortly after I posted
>that question and it said that water wasn't an issue. (Although the lab
>techs said NO WATER after the glucola, which I can understand a bit more
>since I am thinking it "might" lessen the effect of the sugar somehow.
>Not sure but who knows?) However I do have another question re: these
>tests: when I took the first test it was a non-fasting 1 hour GTT and
>that is the one that I failed. The second test I took was the fasting 3
>hour GTT. According to my MD after an hour of taking that first test
>blood sugar above 140 was an indication of possible gestational
>diabetes. When taking the 3 hr. GTT the first hour blood draw revealed
>a level of 153, but according to my MD and the NIH this is perfectly
>acceptable as it would have to be 190 mg/dl or higher to be considered
>part of a diagnostic criteria (with 120 mg/dl being the normal mean
>value) I have other women telling me that they took the 1 hour GTT as a
>fasting test and I am wondering if A) the diagnostic criteria are the
>same and B) what would the difference be between the cut off of 140 for
>the 1st take and the higher level of the second test? I am not panicking
>or anything I am just curious to how the data is assimilated and why
>patients are instructed differently in the 1 hr. GTT? Thanks for your
>insight.
>
>At Wed, 30 Aug 2000, Lynn D. Montgomery, MD wrote:
>>
>>At Wed, 30 Aug 2000, Ann wrote:
>>>
>>>Hi:
>>>
>>>I posted earlier this week when I found out I had failed my one hour
>>>test. I had a question then and I have another one now.
>>>
>>>Today I took the 3 hour GTT. I drank about 24 oz of water about an hour
>>>and a half to an hour and forty-five minutes before beginning the first
>>>blood draw. (the fasting blood draw). Could that skew the results in
>>>any way? Also, when I went back to take the second blood draw, the
>>>phlebotomist was 15 minutes late in taking my blood so instead of it
>>>being an hour after the glucola, it was an hour and fifteen minutes.
>>>Would that have skewed the data? I went back to take the other two blood
>>>draws on time from the original start of test time (time from which I
>>>drank the glucola) so I they were uneventful. Neither girl could give
>>>me an exact answer re: these two questions although they did both say
>>>that you cannot drink water after the test has begun. Please advise. By
>>>the way, the test both came back normal.
>>>
>>>Thanks for your input.
>>
>>Ann,
>>Neither the drinking water or the 15 minute late draw should
>>significantly affect the test...
>>Lynn
>>
>>--
>>Lynn D. Montgomery, MD
>>Director, Maternal-Fetal Medicine
>>Rocky Mountain Perinatal Center
>>Missoula, Montana
>>
>>**Note: Opinions expressed here are for educational purposes only and, as such, do not constitute a physician-patient relationship. This information is not intended to supplant the need for you to consult with your physician prior to choosing therapeutic options and/or interventions.
>>
>>**Private e-mails cannot be entertained due to time constraints, consequently no private e-mails will receive a response.
>>
>>**Thank you for your understanding ;-)
>>

The one hour test is designed to be a screening tool that does not require the patient to be fasting. This is accomplished by the fact that the test is only one hour and there is a 50 gram glucose load, thus the state of diet isn't really a factor. The three hour test is a 100 gram load, thus the higher 1 hour values. It is designed to be a fasting study, incorporating the fasting blood glucose value as one of its four values... Lynn

--
Lynn D. Montgomery, MD
Director, Maternal-Fetal Medicine
Rocky Mountain Perinatal Center
Missoula, Montana

**Note:  Opinions expressed here are for educational purposes only and, as such, do not constitute a physician-patient relationship.  This information is not intended to supplant the need for you to consult with your physician prior to choosing therapeutic options and/or interventions.

**Private e-mails cannot be entertained due to time constraints, consequently no private e-mails will receive a response.

**Thank you for your understanding ;-)

Next message: Lynn D. Montgomery, MD: "Re: Salt & Pregnancy"
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