OGTT - Oral Glucose Tolerance Test?

#1

Has anyone had this test? I ask because I was shown some data from a patient who had normal HbA1c, normal fasting glucose, normal fasting insulin, normal triglycerides and liver function. Normal defined being in the ranges. Yet his postprandial insulin levels were off the chart from 30 minutes on.

(You've tried everything else; why not try bacon?) #2

The late Dr. Joseph Kraft believed that the results of the oral glucose tolerance test showed diabetes far earlier (up to 20 years) than the standard diagnostic, which is loss of glucose control. He identified five patterns of insulin response, one of which is healthy, and the rest indicators of incipient diabetes.

Dr. Kraft called the phenomenon "diabetes in situ or “occult diabetes.” The terms used for it today are “pre-diabetes,” “insulin-resistance,” and “metabolic syndrome.”

Just one caveat: If you have an OGTT on a keto diet, the results will be skewed, because of the missing first-phase insulin response. This can freak out your doctor. On a high-carb diet, the pancreas maintains a store of insulin for immediate release, but on keto the pancreas doesn’t need that supply, so it lets it go. If your doctor understands ketogenic eating, he or she will take it into account when interpreting an OGTT, but if keto is not on your doctor’s radar, you can eat carbs for a couple of days before the test, to make the results look “normal.” It takes the pancreas about 24 hours, apparently, to build its insulin store back up and provide a good-looking first-phase response.

#3

Yes, I have been having these tests for years, initially at my request because in the 90’s I knew I was insulin resistant and wanted to avoid becoming diabetic. Unfortunately then there wasn’t helpful information available.

The “normal” data was obtained from a non-challenging test situation.

The benefit of the OGTT is that you get the real time data of your insulin and blood glucose levels as they exist when you eat or are exposed to glucose.

My insulin levels are high at a morning fasting test and off the charts for a OGGT. It is the OGTT results that have always guided me.

I avoid the OGTT these days because I know I have type 2 diabetes and exposing myself to all this glucose I regard as toxic.

(Bob M) #4

Do you know where the patient got this done? I can no longer find anywhere that does a Kraft test (which is basically OGTT + multiple insulin readings).

#5

An OGTT will almost always fail on keto. Most pregnant women on keto who have been put through it ( to test for gestational diabetes) fail this for reasons mentioned by Paul. Unless a doctor understands how keto affect OGTT results, they almost always just rule it as gestational diabetes.

Eating high carb for a week before the OGTT is the usual work around for this. Which sounds awful especially during pregnancy - all that sugar yuk. Some doctors accept the results of a cgm though.

If not on a keto diet though, could have a different interpretation.

#6

I just asked the doctor for a request for glucose tolerance test with insulin levels …it was never a problem to get the insulin levels.

#7

Look for the test that measures both glucose and insulin, sampling at the 30min mark. (its rarely done) Takes about 2 hours to complete, 4 blood draws and the worst part is you have to consume a disgusting bottle of pure glucose. Search on line and you will find.

#8

It’s becoming an outdated way of doing things, 30 minutes isn’t long enough to tell anything, though. Most people aren’t completly recovering from 75-100g pure glucose hit in 30 mins regardless of how insulin sensitive you are. That’s an unrealistic expectation. Unless every time you injest carbs it’s 75-100g of pure glucose.

A1C is only good IMO if you always eat good, way to easy to skew it. Eat awesome half the time, eat like garbage and crash half the time, the average will be good.

#9

Read the entire post. “2 hours long to complete, 4 blood draws.” 30, 60, 90, and 120 minutes.

(Bob M) #10

No doctor I know of will order this test.

Can anyone show me equivalent tests anywhere online? Labcorp doesn’t have it. Quest doesn’t have it.

Maybe you could get an OGTT and then get multiple insulin tests too, and tell the phlebotomist when to take them. I’m not sure about that.

I had a 2 hour Kraft test done a few years ago, but that doctor is long gone and the other doctors at the same place she was thinks she was a quack. I can’t figure out what she ordered.

(You've tried everything else; why not try bacon?) #11

I thought an OGTT consisted of an insulin level at baseline, a 75 mg glucose load, then insulin and glucose measured at 30, 60, 90, and 120 minutes. What other type of test are you thinking about? Sorry, but I’m not quite sure what we’re talking about anymore.

(Bob M) #12

The one I got was 75 g glucose. Blood sugar measured before then at 1 hour and 2 hours.

Some people include 30 minutes. Some suggest going longer than 2 hours. The one you suggest has every 30 minutes.

Regardless, it’s a moot point anyway, because I can’t find these – anywhere. Can’t order one.

Edit: For instance, I contacted Siobhan Huggins from Own Your Labs. No such test exists, and they use LabCorp. No such test exists at LabCorp.

This all I can find that’s close, and it just uses insulin and c-peptide:

https://www.questdiagnostics.com/healthcare-professionals/about-our-tests/diabetes-pre-diabetes/early-diagnosis/irscore

I cannot find any location to get a Kraft test.

If anyone knows of one, let me know.

(You've tried everything else; why not try bacon?) #13

Thanks for the explanation, Bob. So an “OGTT” means measuring glucose only, and very few measurements, at that. Sheesh!

#14

In Australia, the doctor simply requests the insulin levels be taken as well as glucose levels and then you have the additional info (re insulin) that Kraft recommended.

Even if they didn’t really understand why I wanted it, I never had a doctor refuse the request, in the 25 years I was getting them.