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Date of last update: 10/17/2017.

Forum Name: Diabetes

Question: Can glucose tolerance test results be invalid?

 ladonnascott - Fri Sep 12, 2008 12:02 pm

I gave birth three months ago. I had gestational diabetes during pregnancy. At 9 weeks postpartum I had a 2-hr glucose tolerance test. The results were: fasting 86, 1-hr 185 and 2-hr 225. My midwife then refurred me to an endocrinologist. I have since been testing my blood sugars again and they have all been within 85-120. This is with eating McDonalds and sugary foods as well. I am wondering how it would be possible to have diabetes and have perfectly normal blood sugar readings. I even borrowed a friends meter, and his meter was within 3 points of my own, so I know it's accurate and calabrated also. I had asked my midwife to let me take the 2-hr again, since I had some doubts about the results. They refused... First of all, I was having a very heavy period and I've read that this can effect blood sugar levels. Also my meter has an option to mark a reading with "menses", so I know this to be true (even though my midwife and the nurse said otherwise). Second, they forgot (and I didn't think about it until later) to tell me to bulk up on carbs for three days before the test, and I was dieting, so my carb intake was drastically lower than normal. Third, I took the test at 2:30 pm after having had two cups of coffee with my breakfast at 6:30 am (8 hours of fasting, but not tested first thing in the morning). Could the test be wrong? If I were to have the test redone (which the endo says he would do) and it still shows high, even though my own results are normal, what does that mean? Is it possible to have diabetes and still have totally normal readings all the time? Should I take this as a sign that I have a precurser to diabetes and just keep eating healthy and dieting? Should I bother to visit the endocrinologist? Thanks!
 John Kenyon, CNA - Mon Nov 03, 2008 10:36 pm

User avatar Hi there -

You need to have a second GTT as well as a hemoglobin A1C test, to determine if the findings are consistent. There was enough wrong with the circumstances of the first test to make it probably invalid. Second, since you had gestational diabetes you're more likely to have metabolic abnormalities which may well resolve over time. If your home tests are in the range you describe, then you either are coming down from the gestational form and may well stabilize at normal, or you may have what's often called "prediabetes", which may or may not evolve into confirmable diabetes. By all means keep living a healthy lifestyle as you are now, especially since there is some slight question about your ability to metabolize sugars, but it sounds like right now you really need a proper recheck and hemoglobin A1C test done. If they come out within normal limits you can pretty well stop worrying about this. If they show something else, you'll probably have to be followed (at least with occasional 8-12 hour fasting glucose tests) for a while. If that all comes out clear then, again, you'll be able to relax.

I'd see the ednocrinologist for sure. Get this out of the way one way or the other. Best of luck to you.
 joenauta - Sat Jan 03, 2009 4:41 pm

I am constantly thirsty and peeing frequently. I went to the hospital, the doctor gave me a random blood glucose test and it turned out to be 96. He said I'm not a diabetic. Do I take his opinion or not. The thirst and urination has me worried. I tried to go to sleep at 8 and I urinated 5 times before 9p.m. before i was able to go to sleep. Does peeing a lot and drinking lots of water lower your blood sugar before that test? Your advice would be greatly appreciated.
 John Kenyon, CNA - Sat Jan 03, 2009 9:06 pm

User avatar Hi again -

There's a whole long list of possible causes of frequent urination and thirst (one follows the other), and while some can be serious, most of the time it is a temporary metabolic imbalance. If this persists you may have to have a different sort of test, a 24-hour urine test, to determine if there's something funny going on with your adrenals. I say this because you are looking less and less like a diabetic, and no, the frequent drinking and urination wouldn't alter your blood sugar, at least not enough to keep you from registering in the diabetic range. In fact, your ER glucose reading totally defies diabetes as a cause of the other (new) symptoms. I still think you should have at least a hemoglobin A1C test, which would be able to tell if your blood sugar has been elevated over the past few months. This is an excellent guide in diagnosing diabetes, and an essential occasional test for known diabetics, to be certain the condition is well-controlled. I strongly suspect you don't have diabetes, but it's not completely impossible, so this test would be very helpful in ruling it out once and for all. Then, if the thirst and urination continue, you can consider ruling out adrenal problems, which may also not be present (again, this can just happen sometimes, for a stretch, then return to normal).

Please keep us updated. We'll be right here.
 joenauta - Sun Jan 04, 2009 7:13 pm

I think you're replying thinking I am somebody else. How am I looking less and less likely to be a diabetic? That was my first post. I think you're mistaking me for the person who initiated the post.
 joenauta - Tue Jan 20, 2009 12:55 am

Is this normal or am I making too much of this? I ate three slices of ham with rice. Blood Glucose @ 2 hours was 96. But Blood Glucose @ 3 hours was 107. I thought Blood Glucose peaked 2 hours after eating.
 John Kenyon, CNA - Mon Jan 26, 2009 11:51 am

User avatar Hi -

It appears I did what you said, yet the response still is valid, as your question rather overlapped the content of the first poster's questions. I apologize for mistaking you for someone else (new questions are usually posted in separate threads so it's easy to not realize one is responding to a different poster). Again, though, I'd stand by the answer as totally appropriate to your question.

Further, regarding the 2-hour post-prandial glucose "peak", as with all things it is an average, not an ironclad rule. Our glucose levels change throughout the day depending upon a lot of different factors including activity (or lack of it), stress (or relief of stress), etc. A small increase in blood glucose beyond the 2-hour window is not abnormal, and yours was certainly still within an acceptable range. There is a phenomenon known as post-prandial dip, wherein glucose levels actually drop after a generous meal, then slowly rebound. This could also explain the difference, although it's really close enough to normal to not warrant any further investigation anyway.

Hope this is helpful and again I apologize for not realizing who I was addressing when I wrote the reply -- even though it turns out to be the right answer anyway. :)
 joenauta - Wed Jan 28, 2009 9:27 pm

No apology necessary. I guess it was a minor misunderstanding.
 John Kenyon, CNA - Thu Jan 29, 2009 1:31 am

User avatar Thank you. I just wasn't paying close enough attention to the patient names. Your question seemed to fit the issue already brought up. I've got my glasses on now. :)
 joenauta - Fri Mar 06, 2009 4:46 pm

I went to my appt. My fasting was 98, they gave me an a1c and the result was a 74. The doctor said I'm not diabetic. Now the doctor wants me to get a post void urinary ultrasound.
 John Kenyon, CNA - Mon Mar 09, 2009 2:10 am

User avatar So far so good, then. Please update us as to the results of the ultrasound. I'm happy to hear the tests showed you're not diabetc. Continued good luck!

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