3 Hour Glucose Tolerance Test

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Re : 3 Hour Glucose Tolerance Test

Postby blythe » Sat Jul 28, 2007 00:33 am

Hi Kim! I just about lost my mind when I failed the 1-hour screening test with baby #2- I was all prepared for PE, then totally blindsided by failing the GD screening. I passed the 3-hour, but did tons of internet research anyway. As near as I can tell, the 150-a-day unrestricted carbohydrate diet is more a "research" thing - a way to standardize everyone's results. I've read that the carb-loading before the test is a American Diabetic Association recommendation, but have never been able to find the actual ADA statement, or the rationale behind it. For what it's worth, in this study (full text):


says "The test was performed at 8–9 am after an overnight fast of not less than 8 hours and after 3 days of unrestricted diet with at least 150 g of carbohydrates daily."

And "Kmom" http://www.plus-size-pregnancy.org/gd/gd_testing.htm
go to the section "More on the Three-Hour, 100g Diagnostic Test (Glucose Tolerance Test)"
"Generally speaking, the woman is supposed to "carbo-load" for several days before a GTT. This apparently stimulates her body to produce more insulin and be more prepared for the overload of the 100g test. However, many doctors do not instruct their patients on this at all, and some even forget to tell the patient to fast ahead of time. In addition, even those who tell their patients to carbo-load do not give consistent advice. Some give a specific diet to follow, specifying exactly how many extra carbs to eat and when (usually >150g--10 servings or more--of carbs per day; remember that carbs in this case includes all starches, fruits, sweets, and dairy products). On the other hand, other doctors just tell the woman to eat a few extra servings of carbs 1-2 days before the test. Be sure to press your doctor for more details on this and question your care closely if the doctor seems careless in attitude towards the test protocols. The official recommendation is to carbo-load for at least 3 days before the test, but since many doctors do not follow this, the lack of uniform testing conditions is a major criticism of this test."

And finally, http://jcem.endojournals.org/cgi/conten ... /43/5/1088
"Effects of carbohydrate restriction on the hypoglycemic phase of the glucose tolerance test"
seems to say that restricting carbs before the test increases _hypoglycemia_ in normal individuals (but pregnant women weren't tested and pregnancy is one of those things that change the way your body processes sugar so dramatically that I hesitated to even include this study because they only tested "normals").

Not a doctor here, but since you're already on metformin (for PCOS?) that makes me think your body already does whacky things with sugar, and throw pregnancy into the mix and you probably do have GDM (gestational diabetes mellitus). Since your random numbers are fine, I wonder if your diet is just already good enough to control it?

I really like the Kmom site (GDM index at:) http://www.plus-size-pregnancy.org/gd/gd_index.html
If you have your numbers from the 3-hour you can even compare them to her charts. It's been a while since I've read it closely, but it seemed like the fasting number was a big indicator of whether you need insulin or not (over 105 fasting = insulin).

For what it's worth, a midwife told me that women who eat protein-heavy diets in pregnancy tend to fail the 1-hour screening, but pass the 3-hour no problem. Since you failed the 3-hour also, that also makes me (non-doctor) think that you have GDM.

The good news is that if your random numbers are fine, you won't need to change much at all!

(Oh! I'm pretty sure I've read that if your fasting # is above 105 or your 1-hour is over 200, most docs will skip the 3-hour and automatically put you on insulin. More http://www.plus-size-pregnancy.org/gd/gd_testing.htm
Absolutely look at other sites, too, but in my reading, Kmom seemed to follow the research pretty accurately and tried to be balanced about whether GDM is dangerous for mom and baby or overemphasized and overdiagnosed...)

Whew - hope something in all that is helpful [:)]!

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Re : 3 Hour Glucose Tolerance Test

Postby misty costner » Fri Jul 27, 2007 09:48 pm

I took these tests last month. I miserably failed the one hour test, with a score of 180 or so. Then I easily passed the three hour test. No one could believe it.

According to my doctors and the lab I visited, you can eat normally before the test (I avoided sugar and fruit for three days) and fast after 12 am. I took the test the first thing the next morning.

I was excited that I didn't have gest. diabetes, but only for a short time, because that was the day I started spilling protein, and the PE seemed to swing into overdrive.

Good luck to you.

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Re : 3 Hour Glucose Tolerance Test

Postby ecfeeney » Fri Jul 27, 2007 04:06 pm

Hi...the three hour is pretty accurate...It was my fasting sugars that were do la la...You really need to chat to an endocrinologist. I think if you were going to fail the test you were going to fail regardless. I have GD and Hypertension, and i was told today that although I'm losing weight??? my baby at 35.3weeks is 7pounds with abnormal growth. It was quite a shock. My first baby wasn't this weight at three months old! lol...My numbers were good too from 28-30weeks and started to get much more difficult to control later on. Again it's all due to a strange placenta...Good luck...

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Re : 3 Hour Glucose Tolerance Test

Postby kara » Fri Jul 27, 2007 12:12 am

I thought it was standard practice to have a 3 hour done when you fail the one hour. The 3 hour is more accurate from what I've heard. Maybe ask to retake the 3 hour and eat a normal diet prior to the test. Also, they usually ask you to fast prior to the test (at least the 1 hour), so ask about that as well.

Good luck!

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Re : 3 Hour Glucose Tolerance Test

Postby emersons mom » Fri Jul 27, 2007 12:01 am

just chiming in that i failed the one hour and was labeled gd, put on the diabetic pregnant diet, then put on insulin when my finger sticks started going too high (in the 130-150 range after a meal) and suddenly about 4 weeks after insulin I was hypoglycemic...too low with finger sticks could not drive but the dr kept me on insulin....convinced i was having sumo baby.......i just think all my whacky blood sugars were thanks to my badly operating placenta.....wonder why they never gave me a three hour?

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Re : 3 Hour Glucose Tolerance Test

Postby bookworm » Fri Jul 27, 2007 10:17 am

With baby #2, I failed the 1 hr glucose spectacularly and had to do the 3 hr. My dr's office said to eat a normal diet beforehand. I did some online reading about the "carbo-loading" diets that some dr's recommend before the 3 hr test, but it does not seem to be supported by evidence (and could be dangerous if you truly are a gestational diabetic and don't know it yet).

I did read that a low-carb diet prior to the 3 hr test is thought by some researchers to affect metabolism in a way thats make the body somewhat less able to process the sugar you take in during the 3 hr test. The idea is that a low-carb diet can cause your body to downregulate its sugar processing machinery, and then when you flood your body with sugar during the test it's unprepared. Do bear in mind that this is just a theory - and it seems doubtful that just a few days on a low-carb diet would have much effect.

Turns out that I passed my 3 hr with FLYING colors. My dr thinks that I failed the 1 hr (seriously failed - they were sure I'd need insulin) because I was taking benadryl and antibiotic at the time for cold/bronchitis. Apparently benadryl can affect blood sugars. Any chance you had been taking meds that could have affected your 3 hr?

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Re : 3 Hour Glucose Tolerance Test

Postby ozierja » Fri Jul 27, 2007 08:49 am

The 3 hour GTT tests how quickly you process the sugars and is pretty "controlled" so to speak. Everyone gets the same amount of sugary drink and waits the same amount of time to see how the body processes it. The random test can have many factors influence the results. Does that make sense? Just something to consider...it would seem that the 3 hour GTT is more reliable.

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3 Hour Glucose Tolerance Test

Postby kimpaulus00 » Fri Jul 27, 2007 07:24 am

I was wondering if anyone knew the protocol for diet prior to the 3 hour GTT?

My 3 hour came back with numbers so high that my OB figured that I would need insulin (even with the fact that I am on a good bit of metformin). However, they drew a random glucose the same day that I learned the results and the number on the random glucose was 107 (which was great considering that I had juice earlier during the NST). But, I had already been sent to some Diabetes Care Center and told that I had gestational diabetes -- I have been monitoring and all of my numbers have been absolutely beautiful.

So, I am wondering about the accuracy of the 3 hour (as is the OB nurse). I did some research and found that several web sites said that a person should eat a normal diet or a diet with at least 150 grams of carbs per day for three days prior to the test. I was not told this and instead figured that a low carb diet would be better, so during the few days prior to the test, I ate very few carbs.

Any ideas or similar experiences?


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