Examinations
Examinations
Hemoglobin consists of four protein-containing subunits. Each subunit in red blood cells contains a heme group and red-colored protein. Its main function is the transport of oxygen and carbon dioxide in the blood. Each hemoglobin molecule can bind to four oxygen molecules. Hemoglobin molecules consist of various fractions and derivatives. HbA1c, a component of the heterogeneous group of hemoglobins, is one of many glycated hemoglobins, meaning it is a subfraction formed by the attachment of various types of sugars to hemoglobin.
The formation of HbA1c occurs in two stages:
- A reaction between glucose (non-enzymatic) and the N-terminal amino group of the beta chain of hemoglobin (HbA) results in the formation of labile HbA1c (reversible aldimine).
- Stable HbA1c (ketoamine) is also detected in the blood of healthy individuals.
The rate of this reaction and the amount of glycohemoglobin formed depend on the average blood glucose concentration during the lifespan of red blood cells (approximately 120 days). This reaction produces several forms of glycohemoglobin: HbA1a, HbA1b, and HbA1c, with HbA1c being the most quantitatively significant and closely correlating with diabetes severity.
HbA1c reflects hyperglycemia over the lifespan of red blood cells, serving as an average indicator of carbohydrate metabolism during this period. Normalization of HbA1c levels occurs 4–6 weeks after blood glucose levels are stabilized. In diabetic patients, HbA1c levels can be 2–3 times higher.
WHO Recommendations:
This test is considered optimal and essential for predicting diabetes. Diabetic patients are advised to take this test every three months. To guide diabetes management, maintaining HbA1c levels below 7% is recommended. Results above 8% indicate the need to adjust treatment strategies.
Clinical studies show that a 1% increase in HbA1c corresponds to a 2 mmol/L rise in blood glucose levels, which helps assess the risk of diabetes complications. Lowering HbA1c by 1/10 reduces the risk of diabetic retinopathy by 45%.
- Sample Type: Venous blood.
- Do not eat for 2–3 hours before the test. Drinking water is allowed.
- Avoid physical and emotional stress 30 minutes before the test.
- Refrain from smoking 30 minutes prior to the test.
- Monitoring blood glucose levels in diabetic patients to minimize damage to the kidneys, eyes, cardiovascular, and nervous systems.
- Assessing the average blood glucose concentration over 2–3 months.
- Verifying the effectiveness of diabetes treatment and determining if adjustments are needed.
- Detecting uncontrolled blood glucose spikes in newly diagnosed diabetes patients.
- Preventive diagnosis of early-stage diabetes.
- For Type 1 or Type 2 diabetes, the test is conducted 2–4 times a year, depending on treatment quality.
Additionally, the test is performed for patients suspected of diabetes with symptoms such as:
- Extreme thirst
- Impaired vision
- Increased susceptibility to infections
- Fatigue
- Frequent and excessive urination
Factors Affecting Results:
- Low glycohemoglobin levels may occur in patients with abnormal hemoglobin forms (e.g., anemia).
- Conditions such as anemia, hemolysis, or significant blood loss can lower results.
- Conversely, recent iron deficiency or blood transfusion (conserved blood contains high glucose levels) may raise HbA1c levels.
HbA1c (%) | Assessment |
4–6.2% | No diabetes |
>6.5% | Diagnostic criteria for diabetes |
5.7–6.4% | High risk of diabetes and its complications (as per ADA criteria) |
6–6.5% | High risk of diabetes and its complications (as per WHO criteria) |