Test that measures the proportion of sugar bound to hemoglobin molecules, reflecting average blood glucose control over the past 2-3 months. Used in the diagnosis and follow-up of diabetes.
Indication
- Supporting the diagnosis of diabetes (may be used alone in symptomatic patients)
- Follow-up every 3-6 months in known diabetic patients
- Adjustment of diabetes medications or insulin doses
- Screening in individuals at high risk of prediabetes
- Evaluation in eligible risk groups as part of an annual check-up
- Pre-pregnancy diabetes control assessment
Preparation
- Fasting is not required for HbA1c; it can be drawn at any time of day
- Recent blood draws or transfusions should be reported to the physician
- If there is a history of hemoglobinopathy (thalassemia, sickle cell anemia), the physician should be informed; results may be affected
- Conditions such as iron deficiency anemia may distort HbA1c results
How it's performed
- Approximately 2-3 mL of blood is drawn from an arm vein
- Blood is placed in a purple-cap (EDTA) tube
- Glycated hemoglobin percentage is measured by HPLC or immunological methods
- Results are reported in % (NGSP); some laboratories also report IFCC mmol/mol units
- Results are usually available the same day or within 24 hours
Post-procedure
- Results are evaluated together with the clinical picture and accompanying tests
- If diabetic patients have reached the target, current treatment is continued
- If above target, nutrition, exercise, and medication doses are reviewed
- Follow-up every 3-6 months is recommended
- In conditions such as anemia, hemoglobinopathy, or pregnancy, alternative tests such as fructosamine may be considered instead of HbA1c
Risks
- Temporary bruising or sensitivity at the blood draw site
- Rare hematoma
- Brief lightheadedness due to needle anxiety
- Very rarely, local infection
FAQ
What should the HbA1c value be?
General reference: below 5.7% is normal, 5.7-6.4% is prediabetes, and 6.5% or above on two measurements is significant for diabetes. For most adults with diabetes, the target is generally below 7%; the target is individualized based on age, comorbidities, and hypoglycemia risk.
Do I need to come fasting?
No. Because HbA1c reflects the average over the past 2-3 months, it is not affected by fasting or meal timing.
How often should I have it checked?
In diabetic patients, every 3-6 months is generally recommended. After a treatment change, a follow-up within 3 months is appropriate. In non-diabetic individuals, routine screening is performed according to the physician's recommendation.
Can HbA1c be misleading?
Yes. Iron deficiency anemia, chronic kidney failure, pregnancy, recent transfusion, and certain inherited hemoglobin disorders can affect the result. In these cases, the physician may request additional tests.
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