Hemoglobin A1C

Test Mnemonic


CPT Codes

  • 83036 - QTY (1)




  • Glycosylated Hemoglobin
  • Glycosylated Hemoglobin


  • Hemoglobin A1C
  • Estimated Average Glucose

Performing Laboratory

Cleveland Clinic Laboratories

Specimen Requirements

Volume Type Container Collect Temperature Transport Temperature Special Instructions
2 mLWhole bloodEDTA (Lavender) Refrigerated 

Minimum Specimen Requirements

Volume Type Container Collect Temperature Transport Temperature Special Instructions
0.1 mL     


Environmental Condition Description
Ambient5 days
Refrigerated14 days
Frozen7 days

Days Performed

Sun - Sat

Turnaround Time

24 hours


Name Description
High Performance Liquid Chromatography (HPLC) 
Ion Exchange Chromatography 

Reference Range

Hemoglobin A1C
Sex Age From Age To Type Range Range Unit
       Normal4.3 - 5.6%

Special Info

The HbA1c test is not intended for analysis of samples collected from newborns. The HbA1c test should not be used to replace glucose testing in pediatric patients, pregnant women, or patients with Type 1 diabetes. In cases of rapidly evolving Type 1 diabetes, the increase of HbA1c values might be delayed compared to the acute increase in glucose concentrations. In these conditions, diabetes mellitus must be diagnosed based on plasma glucose concentration and/or the typical clinical symptoms. The HbA1c test should not be used to diagnose diabetes during pregnancy or to diagnose gestational diabetes. HbA1c reflects the average blood glucose levels over the preceding 3 months (the average life of a red blood cell), and therefore may be falsely low during pregnancy or any other condition associated with recent onset of hyperglycemia and/or decreased red cell survival. The oral glucose tolerance test (OGTT) and/or fasting blood glucose test is performed instead for gestational diabetes diagnosis and maintenance. The HbA1c test should not be used to diagnose diabetes in patients with any condition that alters the life span of the red blood cells, including recent blood loss, transfusion, significant iron deficiency, hemolytic anemia (including hereditary spherocytosis) or other hemolytic diseases, hemoglobinopathies and thalassemias, as the altered red blood cell turnover interferes with the relationship between mean blood glucose and HbA1c values. The HbA1c test should not be used to diagnose diabetes in patients with malignancies or severe chronic hepatic and renal disease. Hemoglobin Variants: The most common heterozygous hemoglobin variants (i.e., HbAS, HbAC, HbAD, and HbAE) do not interfere with the test. In the homozygous and double-heterozygous forms of variant hemoglobins (e.g., SS, CC, SC), there is no HbA present; therefore, no HbA1c value can be determined. Other abnormal hemoglobin variants have not been evaluated on the D-100 HbA1c test. Hemoglobin F concentrations up to 30% do not interfere with the test. Any sample with HbF >5% should be suspected of having a hemoglobinopathy. ß-thalassemia trait, as indicated by increased HbA2 concentrations, does not interfere with the test. Labile A1c, as indicated by glucose concentrations up to 1200 mg/dL, does not interfere with the assay. At physiologically occurring concentrations, there is no interference from carbamylated hemoglobin or acetylated hemoglobin. For the confirmation of any particular hemoglobin variant, alternative methods are required. Certain medications may also interfere with the ability to measure HbA1c accurately. Other measures of evaluating glycemic control should be used in patients taking dapsone.

Clinical Info

The hemoglobin A1c (HbA1c) test provides an estimate of a patient’s average level of circulating blood glucose (i.e., blood sugar) over the past 2 to 3 months. The test measures the amount of glucose that has attached to the hemoglobin. The glucose remains bound to the hemoglobin for the lifespan of the red blood cell (typically 4 months). Unlike a standard fasting blood glucose test that reflects the patient’s blood glucose level at a particular point in time, the HbA1c test is not subject to daily fluctuation and is considered a good measure of average blood glucose level over an extended period. Results of the HbA1c test are used to evaluate the treatment of diabetes mellitus. Testing for HbA1c is also used for diagnosis of diabetes in adults, as standardized by the National Glycohemoglobin Standardization Program (NGSP) and the American Diabetes Association (ADA). In diagnosis, HbA1c levels of > or = 6.5% indicate the presence of diabetes, while levels of 5.7-6.4% are considered to identify prediabetes, or increased risk of diabetes. In treatment of diabetes, the HbA1c test is used to monitor long-term blood glucose levels in patients with type 1 or type 2 diabetes. The results of the test can be used by physicians and patients to monitor progress toward treatment goals of lowering the patient’s HbA1c levels over time.