OGTT test - HbA1c: HELP

[sgiossi]

Good afternoon,
A couple of years ago, my doctor prescribed some blood tests. The outcome of the HbA1c was 41 mmol/mol (5.9%), just below the pre-diabetes level. It was strange because my glucose levels had always been fine.
Following the outcome of the blood test, I kept getting tested with home testing kits, and even two hours after eating, I was normally below 8 mmol/L in glucose. The weird thing is that even if before going to bed my glucose is 5.4 mmol/L or less, in the morning when I wake up, it's often 5.6-5.8 mmol/L. There are no diabetes cases in my family.

I had a lab blood test in March: glucose (fasting) 4.98 mmol/L, HbA1c 5.73%.

I tested again earlier today: glucose (fasting) 5.23 mmol/L, HbA1c 5.45%.

I also had the OGTT earlier today and the result was that after 2 hours glucose was 8.69 mml/L (I drank 75 g of sugar).

According to this OGTT test, I am at pre-diabetes level, while HbA1c keeps improving and puts me well below prediabetes. I am not sure, which test is more relevant?

I have been following a diet with reduced sugars and carbohydrates and lost weight in the last two years.

This has definitely improved the level of sugar in the blood but the OGTT tests is at odds with the HbA1c.

I must point out that I took the OGTT test at 10:15 AM (I drank 75 g of sugar at this time), after about 14-15 hours of fasting. The other two tests were taken a couple of hours earlier. Honestly I don't know what to do anymore as I have lost roughly 20 kg in the last 2 years (20% of my weight) because of improved diet.

The downside is that ketones in my urine today was 50 mg/dl, significantly higher than the normal limits, I guess because of a diet poor of carbohydrates.

What should I do? Do I need to worry about the OGTT test?

Many thanks

 

[Ronancastled]

According to this OGTT test, I am at pre-diabetes level, while HbA1c keeps improving and puts me well below prediabetes. I am not sure, which test is more relevant?

Greetings @sgiossi
Congrats on dropping your A1c.
In regards to your OGTT, did you eat more carbs in the 3 days preceeding, the advice is to eat >150gs of carbs in the days before the test.
If you were eating low carb then the results are skewed.

 

[sgiossi]

Greetings @sgiossi
Congrats on dropping your A1c.
In regards to your OGTT, did you eat more carbs in the 3 days preceeding, the advice is to eat >150gs of carbs in the days before the test.
If you were eating low carb then the results are skewed.

I can say I was careful with carbs only the day before. Bread, rice, fruit, yogurt were included in my diet in the three days before my OGTT. I don't think I reached 150 g a day though, no. It was fairly low carb. I've read this leads to false positive cases. Do you think I have diabetes then?

 

[Oldvatr]

Your ketones are consistent with a low carb diet, and nothing to worry about. That reading indicates a low to medium level of ketosis.

The OGTT result is not startling, and only slightly over the threshold. Here in the UK, an OGTT is only really used for testing for gestational diabetes, and is not used for general diagnosis of diabetes. The oral GTT is dependant on many metabolic factors, and is not an exact evaluation. The intravenous IVGTT is more accurate but is rarely used nowadays.

 

[Lamont D]

The doctors will be looking at other results with the OGTT.
Sometimes the two hours isn't a good diagnosis tool of what is going on because, depending on your own individual digestion system, the spike could be different from others. Early or late depending on your first phase insulin response.
If your getting regular normal fasting BG levels everyday, maybe knowing why the the prediabetic diagnosis?
Perhaps as you say too many carbs over a period that the hba1c covered.
Most doctors go by the hba1c levels for a T2 of prediabetic diagnosis, but it doesn't answer all the questions.

 

[sgiossi]

Your ketones are consistent with a low carb diet, and nothing to worry about. That reading indicates a low to medium level of ketosis.

The OGTT result is not startling, and only slightly over the threshold. Here in the UK, an OGTT is only really used for testing for gestational diabetes, and is not used for general diagnosis of diabetes. The oral GTT is dependant on many metabolic factors, and is not an exact evaluation. The intravenous IVGTT is more accurate but is rarely used nowadays.

Thank you for this. I was very worried about the ketones level, as the normal levels are up to 5 mg/dl. I thought my level could be dangerous . I was the one deciding on getting a OGTT. My UK GP advised to repeat the HbA1c only. Should I disregard the OGTT result? If I look at my HbA1c result, mine isn't even pre-diabetes. What about my diet? Should I still lose weight and keep a low carbon diet? Thank you again for being so helpful.

 

[sgiossi]

The doctors will be looking at other results with the OGTT.
Sometimes the two hours isn't a good diagnosis tool of what is going on because, depending on your own individual digestion system, the spike could be different from others. Early or late depending on your first phase insulin response.
If your getting regular normal fasting BG levels everyday, maybe knowing why the the prediabetic diagnosis?
Perhaps as you say too many carbs over a period that the hba1c covered.
Most doctors go by the hba1c levels for a T2 of prediabetic diagnosis, but it doesn't answer all the questions.

The Hb1Ac levels are normal and constantly dropping. My fasting (lab) levels have always been below 5.6 mmol/L. However, when I take some tests myself at home, I notice some higher levels in the morning after waking up, sometimes 5.7 or 5.8. Levels are usually lower during the day (fasting). Should I continue a low carbo diet? I have lost 20% of my weight and it's obviously getting difficult on that side. A year ago, my doctor advised to pay a little more attention to what I eat. My situation looks like border line between normal levels and prediabetes. My hba1c levels are normal though. Is there anything I can do to improve the situation further? Thank you for your help.

 

[HSSS]

The Hb1Ac levels are normal and constantly dropping. My fasting (lab) levels have always been below 5.6 mmol/L. However, when I take some tests myself at home, I notice some higher levels in the morning after waking up, sometimes 5.7 or 5.8. Levels are usually lower during the day (fasting). Should I continue a low carbo diet? I have lost 20% of my weight and it's obviously getting difficult on that side. A year ago, my doctor advised to pay a little more attention to what I eat. My situation looks like border line between normal levels and prediabetes. My hba1c levels are normal though. Is there anything I can do to improve the situation further? Thank you for your help.

No one test is perfect or addresses every need.

Eg fasting blood glucose is subject to something called dawn phenomenon. That’s a normal and natural process whereby when the liver senses lower glucose levels it adds a bit more to the blood for energy. The most common time this happens is after a longer fast between meals such as overnight. Everyone has a bit of this. Ideally it stops as soon as we are up and able to fend for ourselves. In some people it can be a bit slow to switch off. Type 2 commonly have this issue. It has little bearing on what the rest and vast majority of their days readings are. It’s also typically the last glucose measurement of the day to come into line even after the rest of the day has been great for months or even years. Often for type 2 it will remain higher than some expect even with perfect non diabetic hba1c and amazing rest of the day numbers. Hence looking at the total picture not just one aspect of it.

Also fingerprick readings are not so precise as to mean anything at all in the 0.1- 0.2 differences you identify. I’d go so far as the nearest mmol is about the limit of their accuracy (there are formal guidelines but this isn’t too bad a method in practice to understand it). The higher you are the bigger that “allowance” becomes.

hba1c assumes red blood cells of an average lifespan of 12 weeks and the result is weighted more towards recent weeks than more distant ones. If yours live less or more for whatever reason then it gradually becomes less useful. Some medical conditions do this and likely some people have some natural variation too.

As to whether to continue low carb? Well it seems to have had a beneficial effect on weight and hba1c so far. Do you have more weight to lose? How are the belly to hip or hieght ratios? How do you feel eating this way in general? What about markers like triglycerides often fall and any high blood pressure resolving? I’d caution about returning to your old ways completely, as that would likely mean returning to your old weight and hba1c too. Perhaps there’s a bit of wiggle room though depending on how much difference there is between the old and the new ways of eating. Generally to slow, halt, or reverse weight loss it’s advised to add more proteins and fats rather than carbs for those of with type 2.

 

[sgiossi]

No one test is perfect or addresses every need.

Eg fasting blood glucose is subject to something called dawn phenomenon. That’s a normal and natural process whereby when the liver senses lower glucose levels it adds a bit more to the blood for energy. The most common time this happens is after a longer fast between meals such as overnight. Everyone has a bit of this. Ideally it stops as soon as we are up and able to fend for ourselves. In some people it can be a bit slow to switch off. Type 2 commonly have this issue. It has little bearing on what the rest and vast majority of their days readings are. It’s also typically the last glucose measurement of the day to come into line even after the rest of the day has been great for months or even years. Often for type 2 it will remain higher than some expect even with perfect non diabetic hba1c and amazing rest of the day numbers. Hence looking at the total picture not just one aspect of it.

Also fingerprick readings are not so precise as to mean anything at all in the 0.1- 0.2 differences you identify. I’d go so far as the nearest mmol is about the limit of their accuracy (there are formal guidelines but this isn’t too bad a method in practice to understand it). The higher you are the bigger that “allowance” becomes.

hba1c assumes red blood cells of an average lifespan of 12 weeks and the result is weighted more towards recent weeks than more distant ones. If yours live less or more for whatever reason then it gradually becomes less useful. Some medical conditions do this and likely some people have some natural variation too.

As to whether to continue low carb? Well it seems to have had a beneficial effect on weight and hba1c so far. Do you have more weight to lose? How are the belly to hip or hieght ratios? How do you feel eating this way in general? What about markers like triglycerides often fall and any high blood pressure resolving? I’d caution about returning to your old ways completely, as that would likely mean returning to your old weight and hba1c too. Perhaps there’s a bit of wiggle room though depending on how much difference there is between the old and the new ways of eating. Generally to slow, halt, or reverse weight loss it’s advised to add more proteins and fats rather than carbs for those of with type 2.

Thank you for such a detailed explanation.
I think my values show that I don't have type 2 diabetes but I am sort of borderline case between normal values and prediabetes?
My waist-hip ratio is 0.93. I'm 175 cm and my current weight is about 81/82 kg. During the lockdown, my weight reached more than 100 kg. I must say that my ideal weight is probably around 78-80 kg as I am kind of stocky, with large shoulders. When I was going to gym as well back some years ago, my weight was probably around 79 kg. I had fatty liver for more than 10 years and cholesterol around 232 mg/dl (family issue), but this has suddenly disappear after loosing weight and taking cholesterol improving supplements. My cholesterol is currently around 200 mg/dl, HDL is good and triglycerides 90 mg/dl.
I am fine with eating the way I am eating at the moment and I don't want to go back to my old diet. I'd obviously like to eat some more carbohydrates and sugar, sometimes it would be nice. I have a high level of ketones in the urine probably because of my low carb diet.

 

[HSSS]

Ketones do seem a bit high, even for a ketogenic diet rather than merely low carb as you have described. How many carbs (excluding fibre) are you eating daily?

Urine levels are notoriously a bit more erratic than measuring by blood not least of all because of the subjective assessment of results. This chart shows blood ketone ranges, though I understand urine values are the same.

 

[Hobs]

The weird thing is that even if before going to bed my glucose is 5.4 mmol/L or less, in the morning when I wake up, it's often 5.6-5.8 mmol/L. There are no diabetes cases in my family.

That is not unusual. If you go lowish while asleep, it is not uncommon for your liver to dump some glucose to help keep you functioning as you slowly awake. Read the link below

Dawn Phenomenon (Liver Dump)

Dawn phenomenon is the term given to an increase in blood sugar in the morning caused by the bodys release of certain hormones. It is a relatively common phenomenon amongst diabetics.

www.diabetes.co.uk