Did you happen to do blood tests and not understand the difference between glycemia and glycated hemoglobin? Don’t worry, by the end of this post you’ll be able not only to understand both parameters, but also recognize why they’re so important. You’ll find out their limits and you’ll discover how they can be helpful managing sugars in you organism.
Let’s start from the beginning.
What’s Glycemia?
Glycemia indicate the concentration of glucose in the blood and it is measured in milligrams of glucose per deciliter of blood (mg/dl) and sometimes in millimoles per liter (mmol/L).
Before talking about glycemia, we need to briefly introduce glucose. Glucose is a type of sugar, to be precise it is a monosaccharide sugar and its importance depends on the fact that it is the main energy source of plants and animals, like us.
Human beings take this sugar in the form of complex carbohydrates (like starch) or simple carbohydrates (like sucrose).
In the digestive track these sugars are attacked by enzymes that, like knives do, cut the molecules into many small pieces (including glucose itself), so that they can be absorbed by the intestinal walls.
To make you better understand how this process takes place and how these sugars get into the blood, imagine playing with legos and wanting to build houses and buildings with bricks. Once your beautiful village is built, you have to pass the toys through a perforated wall with holes just wide to allow the passage of the individual pieces.
I know! It’s difficult, but the only solution is to disassemble your toys and pass each brick, piece by piece, through the cracks.
So let’s get to the point!
The constructions represent the complex molecules found in your gut, you are the enzymes that reduce larger non-digestible particles and the perforated wall is the intestinal mucosa.
When glucose passes the intestinal membrane cells, most of it passes into the portal circle (blood flow to the liver). This is why blood sugar rises with a meal. So, as you can well understand, the blood sugar is not stable but it changes in correspondence with food intake.
So, as you can well understand, the blood sugar is not stable but it changes in correspondence with food intake. However we always tend towards homeostasis, therefore some mechanisms, including insulin,restore normal glycemic values.
But what are the “normal” blood glucose values?
We’ll get there shortly.
A wise person puts a pinch of sugar in everything he says to others and listens with a grain of salt to everything others say. Tibetan proverb
If you are interested in the topic of blood tests, read also: “How to raise good cholesterol”.
What is glycated hemoglobin?
To explain what glycated (or glycosylated) hemoglobin is, it is necessary to know what hemoglobin is. This is a protein responsible for transporting oxygen to tissues. During the life of the erythrocyte (red blood cell) it tends to bind to the glucose molecules present in the blood stream in a manner that is directly proportional to the concentration of this sugar. The reaction is called glycation (pardon the pun).
So, how does it differ from blood sugar?
The glycated hemoglobin value provides an indication of the average concentration of glucose in the blood in the three months prior to the blood sample.
Why does this happen?
Everything is linked to the life of the erythrocyte. The red blood cell, in fact, lives an average of 120 days, after which it is destroyed. The glycated hemoglobin in red blood cells reflects the average level of glucose to which the blood cell has been exposed during its life cycle.
I like to explain the concepts of glycemia and glycated hemoglobin through this example.
The speed camera measures the instantaneous speed of the machines at the time of their passage on the meter line, while the safety tutor control system measures the average speed of the machine from the moment the detection begins.
Glycemia represents the speed camera, because it describes the value at the time of sampling, while glycated hemoglobin the safety tutor control, due to the indication of the average referring to a longer period.
One more thing!
There are two types of glycated hemoglobin: HbA1 and HbA1c. The latter is the most stable, which means that it generally does not undergo abrupt changes in relation to sudden changes in blood sugar. For this reason it is usually HbA1c to be measured.
God gave men both a penis and a brain, but not enough blood to be able to shower them both at the same time. Robin Williams
Blood glucose test and reference values
The blood glucose test is usually carried out with a normal blood sample, however it can also be done through the use of glucometers. The latter are portable tools used by professionals or given to people with diabetes to constantly check their glycemic levels.
Blood glucose can be measured fasting (for at least 8 hours) or after a meal (usually after 120 ‘). In this case, the ability of the tissues to pick up insulin signals will be evaluated. In short, the presence or absence of insulin resistance will be detected. Here are the results you might find following the fasting exam:
IFG, or altered fasting blood sugar, means that the biological effect produced by the release of insulin decreases and therefore insulin resistance occurs.
Sometimes the response to ingestion of glucose can be analyzed using an OGTT (Oral Glucose Tolerance Test), which is an oral glucose tolerance test. The test consists in ingesting 75g of glucose dissolved in 250ml of water in 5 minutes after about 12 hours of fasting. A real crap!
The test involves a blood sample fasting (with attached blood glucose measurement) and others with a frequency of 30 ‘following the drinking of the “OGTT cocktail” up to 120’. There is also a simplified test that provides for the detection only at the 0 and at the 120 minute.
Why are the measurements taken after water and sugar rather than after a normal meal?
The answer is to standardize the test.
From the first readings of the test you will notice a glycemic peak that should return (hopefully) with the subsequent samples. In order for you to understand better, here’s what you might find after the measurement at 120 ‘:
IGT stands for impaired glucose tolerance and indicates another diabetes alert condition.
The diagnosis of diabetes is “official” even with a glycemic value of 200 mg/dl at any time of the day, while hypoglycemia occurs below 60 mg/dl.
Please note
Remember that understanding your blood sugar doesn’t provide all the answers. Sometimes it is better to investigate other parameters as well, such as insulinemia.
Examination and reference values for HbA1c
Finally some good news! Sampling for the detection of glycated hemoglobin can be carried out without fasting.
The reference values expressed in the test results for glycated hemoglobin are indicated as a percentage.
Attention!
If there are high concentrations of hemoglobin (as occurs for example in the presence of anemia, haemorrhages or thalassemias) or kidney disorders, the test results may still be altered.
Take home message
We have reached the end of our journey and it is time to take stock.
By now you will have understood that both of the parameters discussed so far are useful for understanding your body’s sugar management capabilities, but which is the most useful?
The best answer is: both of them.
Both values in fact have limitations, however the shortcomings of one are filled by the merits of the other. So the next time you go for a blood test, ask for both. They will also be useful to understand if you are at risk of diabetes and, if so, take action. As long as the values are borderline you can correct the shot and the situation is reversible by improving your lifestyle.
Finally, remember that having a good carbohydrate metabolism is equivalent to burning your “fuel” better and therefore being less likely to gain weight.
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See you soon. Bye!
Photos taken from google images
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