Normal A1c levels can be difficult to achieve in long-standing diabetes. But using the HbA1c is not always the best way to measure success or failure of diabetic treatments.
The hemoglobin A1c test is a blood test used to diagnose diabetes mellitus. You can also use it to monitor the progress and success of treatment.
It gives an average of your blood sugar levels over the past 3 to 4 months.
What is hemoglobin (haemoglobin)
Hemoglobin is a protein found in your red blood cells. It carries oxygen from the lungs to the cells. It also takes carbon dioxide from the cells to the lungs to be breathed out into the atmosphere.
Sugar in the blood attaches to hemoglobin to form glycated hemoglobin, which is commonly known as HbA1c.
The higher the sugar levels in the blood, the more of it binds to the hemoglobin, the higher the HbA1c levels.
Once sugar attaches to the hemoglobin, you cannot remove it.
The only way to get rid of this sugar is to destroy the red blood cell. The average lifespan of a red blood cell is 3 to 4 months. So once it is formed, the a1c (glycated hemoglobin) will remain in the blood to be measured for 3 to 4 months.
The HbA1c is often described as a percentage:
glycated haemoglobin/ total haemoglobin x 100.
How is the HbA1c test done?
You must have a blood sample to check the HbA1c levels. You don’t need any special preparation. That means you can have your blood drawn any time, day or night.
Everybody has some a1c (glycated haemoglobin) circulating in their blood. Your blood sugar cannot be zero or else you’d be dead! In the same way, your HbA1c cannot be zero because you must always have some sugar circulating in your blood.
Normal A1c Levels
- less than 5.7% is normal
- 5.7 – 6.5 is the prediabetic level
- more than 6.5 suggests a diagnosis of diabetes.
Estimated average glucose level (EAG) and abnormal A1c levels
Below is a table that gives the HbA1c equivalents in units you will be more familiar with.
| A1c | EAG (mg/dl) | EAG (mmol/l) |
|---|---|---|
| 6 | 126 | 7 |
| 6.5 | 140 | 7.8 |
| 7 | 154 | 8.6 |
| 7.5 | 169 | 9.4 |
| 8 | 183 | 10.1 |
| 8.5 | 197 | 10.9 |
| 9 | 212 | 11.8 |
| 9.5 | 226 | 12.6 |
| 10 | 240 | 13.4 |
eAG (estimated average glucose levels) = 28.7 X A1C – 46.7
If you don’t want to do the maths, here is a handy calculator you can use to calculate your estimated average glucose levels based on your HbA1c.
Treatment goals for diabetes using A1c
Generally speaking, the treatment goal in diabetes is an HbA1c below 7%. However, this depends on age and other coexisting health conditions. Younger people have lower goals, to help them avoid the complications of having high blood sugar over time.
- less than 6.5% – young patients
- less than 7% – general population
- less than 7.5%-patients
- less than 8.0%-very sick, elderly or frail patients.
For every drop of 1% in the HbA1c, the risk of diabetic complications reduces by about 30%.
Your aim should be to keep your HbA1c level as low as possible without having frequent blood sugar crashes (hypos). Hypos have their own set of complications and can lead to death. You must avoid very aggressive treatment of diabetes to bring the HbA1c level down to a particular number.
How accurate is the A1c test?
The HbA1c test is not a perfect one. Many things can affect the accuracy of this test one way or another.
Blood disorders:
- Blood disorders like sickle-cell anaemia and haemolytic anaemia can lead to a very low HbA1c. They are conditions in which the blood cells are destroyed prematurely, so they don’t survive for up to 3 to 4 months. These result in an abnormally low A1c number.
- Iron deficiency anaemia – In this kind of anaemia, the blood cells live for longer than 3 to 4 months which means that there are more blood cells in circulation at any given time. This leads to a markedly increased HbA1c. The same can be said for any condition where red blood cells live longer than 3 to 4 months.
Diseases of the major organs:
- Kidney disease can affect HbA1c.
- Advanced liver disease can also influence the A1c.
Recent blood loss and recent blood transfusions can also skew the estimated A1c levels.
Disadvantages of the HbA1c test to monitor progression and treatment of diabetes
Measured HbA1c levels can vary from lab to lab, even using the same blood sample. To make sure you have consistent results, you should get your HbA1c test done at the same lab each time.
Another problem is that anything that tampers with the haemoglobin in the red blood cells over the red blood cells themselves can affect the accuracy of the test.