HbA1c/Fasting Glucose Question

[anexpat]

Hello Everyone!

                       To start this topic right, may I give a few statistics I believe are correct, thanks:

 

- Healthy HbA1c is <5.7 %

- Healthy fasting Glucose level is <100 mg/dL

- Fasting Glucose level over 100 mg/dL but <126 mg/dL is prediabetic 

- Fasting Glucose level over 126 mg/dL indicates diabetes

I believe those are the correct numbers?

 

My last medical checkup (12/2019) showed the following:

My HbA1c was 5.4%, so that’s within the healthy reference range (I know HbA1c measures glucose over several (maybe three) months)

 

But my report also said, “Estimated Average Glucose... 108 mg/dL. It did not say if that was for Fasting Glucose or not, I am *assuming* it is, nor does the report indicate that 108 is either above or below the healthy reference range. I am also *assuming* that this 108 number covers the same time period that the HbA1 covered. On the specific date of my check up, my Fasting Glucose was 96 mg/dL.

 

However, if the stats I used when starting this post are accurate, 108 mg/dL *is* prediabetic. 
 

Cut to the chase: my HbA1c is OK, but my Estimated Average Glucose is not, *assuming* the same time period has been covered.
 

This, to me, is a contradiction that I do not understand. Can anybody out there please explain how this can be possible? I *do not* mean to be rude, but I don’t want guesses or assumptions as replies. I’d like to hear from somebody who knows the answer, thanks! This is not just an off the cuff question, a close family member had Type 1 diabetes and passed away far too soon from it.

 

Again, thank you all very much for reading this, I hope 2020 is getting off to a good start for you!

Edited January 21, 2020 by anexpat

[saengd]

The A1C test looks at the problem over a 90 day period and measures glucose attached to hemoglobin molecules, most of which die after 90 days. 

 

An estimated glucose test is just that, an estimated calculation.

 

A fasting blood glucose test is a more precise measurement taken after fasting for at least 10 hours and is also very reliable.

 

The A1C is the one to watch, daily fasting glucose readings will give you a good idea of what to expect and how to adjust your diet daily. I ignore estimated readings.

[thedemon]

You're right that a normal fasting glucose is under 100mg/dl but it's also normal that, depending what you eat, post prandial glucose will be up to 140mg/dl or thereabouts.

 

So 108 is just a mathematical calculation based on your HbA1C giving a 24 hour average. 108 is fine.  

[saengd]

2 hours ago, thedemon said:

You're right that a normal fasting glucose is under 100mg/dl but it's also normal that, depending what you eat, post prandial glucose will be up to 140mg/dl or thereabouts.

 

So 108 is just a mathematical calculation based on your HbA1C giving a 24 hour average. 108 is fine.  

An HbA1C is a 90 day figure, not a 24 hour average.

https://www.niddk.nih.gov/health-information/diabetes/overview/tests-diagnosis/a1c-test

 

 

[thedemon]

2 hours ago, saengd said:

An HbA1C is a 90 day figure, not a 24 hour average.

https://www.niddk.nih.gov/health-information/diabetes/overview/tests-diagnosis/a1c-test

 

 

 

Approximately 3-4 months yes. But what I said is that the figure of 108mg/dl is a 24 hour average. Which it is.

[Sheryl]

4 hours ago, saengd said:

An HbA1C is a 90 day figure, not a 24 hour average.

 

 

The Estimared Average Glucose is derived directly from the HbA1C. It just converts from a score to an average blood sugar reading for the same time frame.

 

But that is average over the whole time period so captures both fasting and post prandial. So the fasting glucose normal ranges don't apply.

 

An EAG if 108 is fine. Not prediabetic.

 

By the way fasting glucose levels are easily affected by stress and some people (myself included) have higher readings on samples done in a hospital than tested at home. My Hba1c is perfectly normal and at home so is my fasting glucose. But on tests done at a lab or hosputal it is a good 10 points higher. A type of "white coat syndrome" or response to the stress of longer without food and painful blood draw (very in my case as they usually have trouble getting a vein).

[PPMMUU]

you can dismissed to "estimated glucose derived from HbA1C"

it is not to be used to diagnosed anything

[oceanbreeze851]

Pre-diabetes is like pre-pregnancy, you either are or not. HbA1C is normal at 4.0 to 5.4. Anything over you are classified as a diabetic. Normal treatment begins when HbA1C is greater than 6.5. Keeping HbA1C between 6.0 and 6.5, means you are controlling the diabetes with medication. If the HbA1C goes below 6.0, the medication should be decreased and if the HbA1C goes above 6.5, the medications should be increased.

[Sheryl]

7 hours ago, oceanbreeze851 said:

Pre-diabetes is like pre-pregnancy, you either are or not. HbA1C is normal at 4.0 to 5.4. Anything over you are classified as a diabetic. Normal treatment begins when HbA1C is greater than 6.5. Keeping HbA1C between 6.0 and 6.5, means you are controlling the diabetes with medication. If the HbA1C goes below 6.0, the medication should be decreased and if the HbA1C goes above 6.5, the medications should be increased.

 

I would disagree with that.

 

Pre-diabetic is a relatively new category but just as "real" as any other categorization. All are classifications adopted by the medical community and subject to change as knowledge advances.

 

Pre-diabetes does  not require medication, but it does warrant life style changes and  more frequent monitoring (No need for daily monitoring, but should probably not go more than a year without a recheck.).

[anexpat]

On 1/21/2020 at 10:50 PM, Sheryl said:

 

The Estimared Average Glucose is derived directly from the HbA1C. It just converts from a score to an average blood sugar reading for the same time frame.

 

But that is average over the whole time period so captures both fasting and post prandial. So the fasting glucose normal ranges don't apply.

 

An EAG if 108 is fine. Not prediabetic.

 

By the way fasting glucose levels are easily affected by stress and some people (myself included) have higher readings on samples done in a hospital than tested at home. My Hba1c is perfectly normal and at home so is my fasting glucose. But on tests done at a lab or hosputal it is a good 10 points higher. A type of "white coat syndrome" or response to the stress of longer without food and painful blood draw (very in my case as they usually have trouble getting a vein).

Thank You for posting this, Sheryl. Most interesting to read! Copied into my notepad for reference! Always good to learn something new... ????
- anexpat

Edited January 28, 2020 by anexpat