In the US, pre-diabetes is usually classified as a fasting glucose over 99 mg/dL (5.5 mmo) and under 126 mg/dL (7.0 mmol). Alternatively, HbA1C of 5.7 to 6.4. Frequently fasting glucose over 99 mg/dL is referred to as impaired fasting glucose. Most doctors test fasting glucose and a standard lipid panel (LDL-C, HDL-C, TG, and Total) as routine test. Some will add a HbA1c. OGTT are rarely done anymore. Where I live I haven't been able to get a doctor to order an OGGT or even a fasting insulin test.
In a standard lab panel, I had a fasting glucose at 107 md/dL (5.9 mmol) which was right after a very stressful event. That got me started looking into my blood sugars. Earlier and later labs showed fasting glucose in the high 80s or low 90s. (In the last four months of eating lowish carb - 80 to 140 grams/day, fasting glucose labs have come down to 84 and 83, so about 7% lower than eating higher carb). Based on the single lab result of 107, my primary care doctor said that I had "impaired fasting glucose" and that I was insulin resistant. He wouldn't however agree to order a fasting insulin test to confirm how insulin resistant. Another doctor ordered a HbA1c and when he saw it was 5.0% (31), he said confidently that I have no blood sugar issues.
Doctors frequently aren't very helpful here, in part, because of the abysmal private insurance system we have, but we can, however, order lab tests online completely outside of the insurance system. (A doctor who has never seen you and who knows nothing about you actually signed the lab order.) The lab draw is made at one of two big national labs - Labcorp or Quest - and you can see the results online about a week later.
I just ordered my own tests which came back:
Fasting glucose 83 mg/dL (4.6 mmol/L)
Fasting insulin 4.1 uIU/mL
HOMA-IR 0.8 (insulin sensitive)
HbA1c 5.0%
That correlates pretty well with the my most recent standard lipid panel:
TG/HDL of 50 mg/dL / 48 mg/dL = 1.04 ratio
Interestingly, my HbA1c didn't change at all after 4 months of reduced carbs. Lower carbs have had a small effect on TG bringing them down from about 70 to 50 mg/dL. I would imagine my insulin would have tested a bit higher if I had had it tested when TG were at 70.
I also ordered an Apo-B since the doctors wouldn't order one. I came back at 61 mg/dL (normal <90 mg/dL, target for extreme risk patients <70 mg/dL). I guess that is reasonably similar to the last two LDL-C which were 53 mg/dL and 69 mg/dL.
My lab tests would seem to say I am healthy, but from testing on my own meters, I know that I have carbohydrate tolerance issues - at least with some large quantities and with some specific types (e.g. hamburger bun spikes me, but whole grain bread I tolerate relatively well).
It appears that my meters consistently read higher than the labs results on fasting glucose. For the latest test, I checked immediately after the lab draw and the meters read:
Relion Premier 97 (5.4)
Contour Next 91 (5.1)
Contour Next One 90 (5.0)
Lab result 83 (4.6)
For the previous test the meters were a bit closer to the lab result, but all the meters were still a far bit higher.
When I get a reading over 140 mg/dL on my meter after eating carbs, due to the accuracy of home meters I can't be quite sure whether than is really 120, 140 or 160, but my guess is somewhere between 120 and 140. But when I see a 170 on the meter and retest on another meter and get 155, I am rather confident that is not a healthy 120 or below reading and probably is above 140 which would put it in the pre-diabetic range.
My concern is to avoid big glucose spikes now, but without the unintended consequence of reducing glucose tolerance (e.g. from eating too much saturated fat?), and to prevent an increase in problems of glucose regulation to would lead to pre-diabetic cardiovascular complications (grandfather died of a heart attack in mid-50s) and certainly try to avoid going down the path to diabetes (grandmother).
At least in my testing, it appears that when I eat more saturated fat my glucose tolerance worsens. The blood sugar takes far longer to drop to baseline. (My body handles a hamburger on a big white bun quite terribly. Not that I frequently eat such ****** food, but from testing I know my body doesn't have a healthy reaction). Also, my fasting glucose seems to be influenced by how much animal protein/fat I eat (I have read that gluconeogenesis is supposedly demand based so I am not sure why protein would have that effect). When I eat a lot of meat my fasting glucose the next day is higher (at least the reading on the home meter seems to be consistently a bit higher).
I would like to know why my body doesn't handle carbs normally. I am not sure if I should order my own OGTT with insulin. (I don't see any point in ordering one without insulin). It would be nice to know if my glucose spikes because of a weak insulin response or because of some type of insulin resistance under stress of lots of carbohydrates. I don't know quite what I would do with the result at this point. If the test shows, high insulin under load, I suppose I could try to lower insulin resistance. If the test shows weak insulin response, what would I do?