Hemoglobin A1c (HbA1c)

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Turnaround Time: Within 1 day
CPT Code:


Test Type: 4 mL Whole blood
Stability Time:



Room temperature

14 days


14 days


14 days

Freeze/thaw cycles

Stable x3

Reference Range:

• Hemoglobin (Hb) A1c: 4.8% to 5.6%

• Prediabetes: 5.7% to 6.4%

• Diabetes: ≥6.5%

• Glycemic control for adults with diabetes: <7.0%


2010 American Diabetes Association's Summary of Glycemic Recommendations for Adults with Diabetes: Hemoglobin A1c <7.0%.

For selected individual patients, providers might reasonably suggest even lower A1c goals than the general goal of <7%, if this can be achieved without significant hypoglycemia or other adverse effects of treatment. Such patients might include those with short duration of diabetes, long life expectancy, and no significant CVD. Conversely, less-stringent A1c goals than the general goal of <7% may be appropriate for patients with a history of severe hypoglycemia, limited life expectancy, advanced microvascular or macrovascular complications, and extensive comorbid conditions and those with longstanding diabetes in whom the general goal is difficult to attain.


Hemoglobin A1c values are used to assess glucose control in diabetes, and in 2010 the American Diabetes Associations affirmed the decision of an international expert committee recommendation to use the A1c test to diagnose diabetes with a threshold ≥6.5%. Point-of-care A1c assays are not sufficiently accurate at this time to use for diagnostic purposes.

Any cause of shortened erythrocyte survival will reduce exposure of erythrocytes to glucose with a consequent decrease in Hb A1c (%). Causes of shortened erythrocyte lifetime might be hemolytic anemia or other hemolytic diseases, homozygous sickle cell trait, pregnancy, or recent significant or chronic blood loss. Glycated Hb F (fetal hemoglobin) is not detected as it does not contain the glycated β chain that characterizes Hb A1c. Specimens containing high amounts of Hb F (>10%) may result in lower than expected Hb A1c.

Factors such as duration of diabetes, adherence to therapy, and age of patient should also be considered in assessing the degree of blood glucose control.

American Diabetes Association. Summary of revisions for the 2010 Clinical Practice Recommendations. Diabetes Care. 2010 Jan; 33(Suppl 1):S3. PubMed 20042773

Bergstrom RW, Kelley JR, Ward WK. Fetal hemoglobin alters hemoglobin A1c measurements. Ann Intern Med. 1991 Oct 15; 115(8):656. PubMed 1716431

Fairbanks VF, Zimmerman BR. Measurement of glycosylated hemoglobin by affinity chromatography. Mayo Clin Proc. 1983 Nov; 58(11):770-773. PubMed 6632974

Holt GS, Wofford JL, Vélez R. Hemoglobinopathies affect hemoglobin A1c measurement. Ann Intern Med. 1991 Jul 1; 115(1):68-69. PubMed 1760005

Krauss JS, Khankhanian NK. HPLC determination of hemoglobin A1c in the presence of the fast hemoglobin I-Philadelphia. Clin Chem. 1989 Mar; 35(3):494-495. PubMed 2920422

Collection Details:

Collection Instructions:

Lavender-top (EDTA) tube, green-top (lithium heparin) tube, or gray-top (sodium fluoride) tube.

The usual precautions in the collection of venipuncture samples should be observed. The sample must be free of clots. Samples with any hematocrit disorders can lead to erroneous results. Send the entire tube to the laboratory.

Maintain specimen at room temperature.