Glucose Tolerance Test questions.

I have to go have a glucose tolerance test. I was talking to my doctor and she said that maybe this will help prove I am a pre-diabetic. I have had an A1C and it came back in the normal range. I have also randomly had my fingers stuck and it is always in the normal range as well. My blood pressure is normal and my cholesterol/triglycerides are normal. I guess what I am curious to know is.. If I pass an A1C what are the chances of me passing the GTT test? Can you pass the A1C and fail the GTT?  When we submit for the surgeon approval in December, I want to have anything and everything I can to prove this is medically necessary. If the GTT test comes back normal, medically I will not be considered as prediabetic. In general what qualifies someones as being pre-diabetic?

Any input would be great!!

Thanks guys!

Pre-D is fasting values between 100 and 125.  A1C is an average, so yes you can still be too high and too low and still have a normal average.  If you can get someone to do a GTT, do so.  it's more definitive.  

Awesome this helps alot! Thank you.

If it is the same as the GTT to test for gestational(pregnancy) diabetes, it is a sugary drink with a measured amount of glucose - you drink it fast - wait an hour - get a blood draw.  The pass/fail number may be different depending on  your lab or doctor - but ideally you'd be at/under 120 or so by one hour after that drink.  There is also a 3 hour version of that test with draws every hour and different pass/fail numbers for each hour.  The 3 hour gives a better picture of what is happening to your blood sugar post-prandial, but the 1 hour test gives a quick idea as to whether or not the 3 hour is worth doing.

Why are you trying to get a pre-diabetes diagnosis? 

There is also a thing called insulin resistance that can come before or with diabetes.  Women with PCOS can have insulin resistance without being diabetic...but it does mess with blood sugar and how your body uses/processes glucose.

I  trying to get that diagnosis of pre diabetic because it counts as a comorbidity and will help my approval process. I am on Medicaid and they require a lot in order to be considered medically necessary. I figured this diagnosis would help.

The A1c test shows what your average blood glucose levels have been like over the last few months.  If they're normal, this probably means your body manages glucose correctly.  However, it could also mean that while you are insulin resistant, you have kept your sugar/carb intake quite low over the last few months so you have managed  your insulin resistance through diet. 

The oral GTT measures how well your body manages glucose in real time.  You drink a great wodge of nasty glucose drink.  Everyone will have their blood glucose rise immediately afterwards as the sugar is absorbed by the digestive system. Normal people will then quickly have all that excess glucose stored in their liver, muscle cells, etc.  (This is done by the glucose being 'delivered' to the cells via insulin. So, two hours later, their blood glucose levels will have dropped back to normal.  In insulin resistant people, their cells ignore the insulin message of "here, take this glucose and shove it in your back pocket until we need it again" (hence, 'insulin resistant') so the glucose keeps wooshing around the blood looking for a home.  So, two hours after the glucose drink, the person's blood glucose will still be at peak (or, at least, quite high).

If you've been on a bariatric diet for the last month or two or three, it's possible your A1C would be normal but your GTT will show you as insulin resistant/pre diabetic. If your diet has been a fairly normal one (by which I mean cakes, lollies, cokes, etc) over the last few months, then more than likely your GTT will show you as normal.

I have been on a low carb low cal diet since I started the program in June. So I figured it couldn't hurt. I've lost 22lbs. But I spoke with the lady from the weight loss center and she said the insurance uses a1c so having a gtt test won't matter as it isn't considered in the list of tests required. But if I fail the gtt, my PCP will put it in my records as me being prediabetic. So I should still do it, right? 

If a normal GTT won't hurt but a failed GTT will help, then yeah, sure, do it!

And, there's a tip for new folks considering bariatric surgery and needing medical proof: for two months before you get a A1c test, eat lots of sugar.  :D