Question about labs--non-Fasting Serum Glucose normal but A1C elevated?

Getting a second opinion from another endocrinologist about treatment. He ran non-fasting labs and I received the following results:

Finger pick in office via meter = 165
Serum glucose = 86 (reference range 70-110)
A1C = 6.5 (reference range 4.8 - 5.6)
Est. Avg. Glucose -140

My last labs in Nov. are as follows:

Finger pick in office via meter = 150
Serum glucose = 121 (reference range 70-110)
A1C = 6.1 (reference range 4.8 - 5.6)
Est. Avg. Glucose -128

Both tests were done by Labcorp.

My question is for the top labs how can the serum glucose be so low since the fingerpick and the A1C closer in alignment? What would skew the serum glucose lab results from last week to be so low?

what meter are you using? In the years between 1992 when I got my first meter and now, I’ve never had a meter reading be higher than the lab results. No matter the meter–the meters have always read lower and I’ve had just about every meter that has been on the US market since 1992. I’ve used LabCorp a lot the past few years.

Accu-chek Nano the original endocrinologist provided free to me to check my sugars. I also use the solution to calibrate be sure that I’m getting the correct numbers.

That’s the reason I am concerned as to why the numbers would be so off. The original endo never said anything about the difference. And the original endo used his meter–I don’t know he uses in his office. With the new endo I used my meter. I will meet with the new endo on the 16th to go over the test results. But I am perplexed by the difference.

There was only about 30-40 minute difference between the finger poke test and drawing the serum glucose test and my BGs do not drop that fast.

That meter should be decently accurate. We have had at least 4 of them and they were fine. However, you should still fingerstick within a few minutes of the lab poke, regardless of how level you feel you may be.

First, there is mainly random chance at play between the fingerstick and the A1C, since the A1C is an average over the last 90 days.

Secondly, despite the accuracy of most meters, including the Accu-Chek Nano, there can still be outliers. The technical requirement is for +/- 20% accuracy - - 95% of the time. I like to test with my own meter right after (or right before) a blood draw or office meter check. It just gives me another datapoint to compare with the lab results. If the office meter is way off from my meter, I might ask for another test.

Thirdly, as @phoenixbound points out there can be a significant change in BG values in relatively short periods of time. If your tests were non-fasting, how close to the test did you have something to eat?

On your earlier test, the difference between the serum glucose and the office meter is 29 points, about a 20% difference from the fingerstick. If there was a significant time lag, I wouldn’t be too concerned.

There was about a 2 hour difference in eating. I ate at around 7 am and my appointment was at 9:30 am. I did the finger test at around 10 am and the lab drew my blood at around 10:30 am.

I thought maybe there could be some compounding factors for the handling of the blood–different locations (same corporation), degradation of blood–fresh factor, serum vs. plasma blood, etc. The Nov. test I went to Labcorp, last week’s test was drawn by a Labcorp-contracted tech working in the doctor’s office and sent to Labcorp. Just guessing on my part since I’m not familiar enough in what happens to the blood after its drawn–how long it sits before it is tested.

There shouldn’t be any degradation of the blood from the blood draw into vacuum sealed, prepared test tubes.

I am not clear on what protocol you are on (metformin, insulin, none, etc), but with a fingerstick variation and the delay, you might be able to explain that large difference.

Right now I’m only on diet and exercise.

I know when they draw my blood for SED Rate testing for RA at Labcorp they have to spin it and test it immediately or else the sample will be no good for testing. The technician has to rush it, it can’t sit in the collection bin. I didn’t know if there was a time limit between the blood being drawn and when it is tested in the case with the serum glucose or not. I know it took a week to view the results in the patient portal. For my rheumatologist I always get my results back within 2 days, 3 at the maximum.

Just checked my labs in my rheumy’s patient portal from March. He always runs a CMP/CBC differential. My blood glucose was 109.

I think 86 is a mistaken somehow, but I don’t what may have happened.

This just my personal opinion after years of testing. There are just too many variables,especially with non fasting, I don’t see much value in non fasting test
For diagnosis .
If I have one test out of five that. Is wildly different I just throw it out. Blood testing is not exact.

Concentrate on your a1c values. But also there there is really not much different between 6.5 and 6.1 with allowable variances.

I agree Fraser. I don’t see the purpose either of non-fasting testing. Just as a monitoring checking, that’s o.k. Since I’m changing endos and asking for a second opinion, I understand where he’s coming from that he wants his own tests.

The old endo didn’t want to move forward beyond diet and exercise. The new endo said I should have been started on insulin since based on my history, medicine list, and labs because my diabetes is steroid induced from my RA.I think the labs were to see if all my spikes are postprandial which most of them are, a few are upon walking, but I count them on one hand.

Thank you all for your feedback.

I think 30 minutes between finger stick and lab draw is way too long. I do my finger stick in the lab and the blood is drawn immediately. No more than 3 to 4 minutes lapses between the two. Last time, I was 120 & lab 127.

The fingerstick was at the request of the nurse and recorded in the desktop in the when I was called back to a room. I was walked to another room to the lab technician after the office visit for the blood draw. I didn’t think about checking my blood sugars again since this was new doctor and trying to follow the technician without getting lost. Actually, I thought they would be giving me a lab slip for me to go to my lab, I didn’t know they had an “in house” technician to draw blood.

My rheumy and old endo always gave me a lab slip and let me take it to Labcorp to draw my blood. And I do check right before they draw–in past the differences haven’t been as noticeable as this one. Now I know for future reference.

30-40 minutes is more than enough time to drop, the finger stick may have been high. I have seen plenty of more than 50 points off numbers on all my devices, finger sticks/dexcom etc. Usually the serum glucose is pretty acurate or close to my meter when I have noticed it and the serum inr was always more accurate to my symptoms than the finger sticks. When my inr was low at the hospital labs I always had symptoms. There could be a mistake/faulty procedure in the serum test too.