For Healthcare Providers

The Power to Change a Life
Starts with an HbA1c test

Turn to Bio-Rad's Hemoglobin Testing Solutions

Choose the Right HbA1c Methology

Not all HbA1c assays are equal. HbA1c testing options on the market generally fall under two major categories: those that reveal hemoglobin variants and those that do not. The diagram below offers a breakdown of each method by mechanism and ability to reveal hemoglobin variants.

HbA1c methodologies
  • "When reporting HbA1c results, it's important for clinicians to know if a hemoglobin variant is present."

    Little RR et al.3

Factors That Interfere with HbA1c Results

Learn more about the importance of knowing when hemoglobin variants are present and how HPLC testing helps give the full patient picture.

  • How do you know what your system doesn’t show?

  • Effect of Hemoglobin Variants on HbA1c Methods

    A Test in Context: Hemoglobin A1c and Cardiovascular Disease by M.O. Gore et al. in the Journal of the American College of Cardiology2

    Some HbA1c assays are affected by hemoglobin variants, which consequently has an impact on HbA1c results. This means HbA1c results may be affected in patients with hemoglobinopathies, such as β-thalassemia or sickle cell disease in patients carrying the sickle-cell trait (HbS), HbC, HbE, and HbD variants, and in patients with elevated HbF.


How HbA1c Results from Different Methods Are Affected by Hemoglobin Variants

Effects of Different Rare Hb Variants on HbA1c Measurement in Eight Methods
by Randie R. Little et al. in the Journal of Diabetes Science and Technology3

To ensure accurate HbA1c results, laboratories must be aware of the presence of hemoglobin variants in a sample. Therefore, it is important to know if patients have a hemoglobin variant and if so, how that variant affects their HbA1c results.

effects if hb char

Can You Afford to Miss One Diagnosis?

  • d-100
  • Evaluation of Lowering the Diabetes Screening Age in Asymptomatic Adults

    by Myers J et al.

    Currently, the Brazilian Diabetes Society recommends screening asymptomatic adults beginning at age 45. In January 2022, the American Diabetes Association lowered the recommended screening age from 45 to 35. In a study by Myers J et al., results from three laboratories in Brazil demonstrated that lowering the age of diabetes screening identifies more potential cases of prediabetes and diabetes. ​

    Download study (EN) 
    Download study (PT)


Clinical Case Studies on HbA1c Interpretation

  • The Good, the Bad, and the Ugly in HbA1c Interpretation

    Trefor Higgins discusses the challenges of HbA1c interpretation when hemoglobin variants are present. He uses real world patient case studies to illustrate those challenges to help clinicians diagnose and treat patients living with diabetes.

  • Confounding Factors for HbA1c Interpretation

    Chris Florkowski presents patient case studies to illustrate the challenges in reporting accurate HbA1c results in the presence of hemoglobin variants, as well as findings from published papers that clinicians should understand when treating patients with undiagnosed diabetes.

  • The Strengths and Weaknesses of HbA1c in Diagnosing Diabetes

    Dave Koch demonstrates how hemoglobin variants and other issues might impact the HbA1c result by sharing patient case studies and data from published papers.

  • HbA1c as a Diagnostic Test and its Role in my Endocrinology Pratice

    David G. Robertson, M.D. shares his insights on managing patients living with diabetes using the HbA1c diagnostic test to help guide healthcare providers


Other Factors that Interfere with HbA1c Results

It is crucial to be aware of factors known to interfere with HbA1c test results when using HbA1c to manage patients with diabetes. The table below provides an overview of factors affecting clinical interpretation of HbA1c.

Factors that Interfere with HbA1c Test Results from Published Sources
Falsely Lowered
Falsely Elevated
Biological Factors Erythropoiesis Increased erythropoiesis:
Erythropoietin/Iron/Vitamin B12 Therapy;1,4,5 Reticulocytosis1;
Chronic Liver Disease1,5
Decreased erythropoiesis1:
Iron2,6 / Vitamin B12 Deficiency;1,4,5 Renal Failure7
Glycation Aspirin (small doses)1,4,5; High doses of vitamin C1,4,5 or vitamin E;1,4,5
Certain hemoglobinopathies1
Chronic kidney disease;5 Alcoholism1,5
Erythrocyte Life Span Shortened erythrocyte life span1,3,5:
Hemolytic anemia;2,3,6 Splenomegaly;1,5 Rheumatoid arthritis;1 Nephritis;3 Liver Disease3; Sepsis3; Certain hemoglobinopathies1; Paroxysmal nocturnal hemoglobinuria;3
Drugs such as antiretrovirals1,4,5, ribavirin1,4 and dapsone1,4
Increased erythrocyte life span1,5,6: Splenectomy1,5,6
Analytical Factors Assay Method Interference Hypertriglyceridemia Certain hemoglobinopathies1,5 Hyperbilirubinemia Carbamylated hemoglobin;1 Certain hemoglobinopathies;1,5 Chronic opiate usage1,4


  1. Geneva: World Health Organization 2011, Use of Glycated Haemoglobin (HbA1c) in the Diagnosis of Diabetes Mellitus: Abbreviated Report of a WHO Consultation, viewed 29 April 2021
  2. NGSP 2019, Factors that Interfere with HbA1c Test Results, viewed 19 May 2021
  3. Lohmann, T.P 2019, The impact of red blood cell lifespan on HbA1c measurement, viewed 20 May 2021.
  4. Unnikrishnan, Ranjit & Anjana, Ranjit & Mohan, Viswanathan. (2012). Drugs affecting HbA1c levels. Indian journal of endocrinology and metabolism. 16. 528-31. 10.4103/2230-8210.98004.
  5. Goel, Shobhit & Sen, Arijit & Sampath, Sangeetha & Tripathi, Preeti. (2020). Hemoglobin E: a potential interferent in measurement of glycated hemoglobin. International Journal of Advances in Medicine. 7. 10.18203/2349-3933.ijam20203609.
  6. O'keeffe, D., Maraka, S., & Rizza, R. (2016). HbA1c in the Evaluation of Diabetes Mellitus. JAMA, 315 6, 605-6. 10.1001/jama.2015.16561.
  7. Garza, M. 2020, Your A1C May Not Be Reliable If You Have Chronic Kidney Disease, viewed 29 July 2021

While many of the above conditions may alter red blood cell production, red blood cell life span and rate of glycation, they can often be picked up by a review of the patient’s medical record or prior laboratory results. Conditions which are clinically silent, however, like hemoglobinopathies which are highly prevalent across Asia and other parts of the world, can be missed resulting in wrong patient care decisions and treatment delays.

The use of an HbA1c assay method that reveals suspected hemoglobin variants (otherwise invisible on other methods) can help you identify patients with clinically silent hemoglobinopathies, allowing you to alert physicians of potential interference on HbA1c test results and/or suggest other methods to manage patients with hemoglobinopathies.

Specific hemoglobin variant and interfering substance claims vary by assay and can be found in the respective assays' Instructions for Use (IFU).


Why Bio-Rad

It is important to choose the right HbA1c testing system to ensure that you and your patient can trust the HbA1c result. Bio-Rad products are recognized as the gold standard for diabetes testing, hemoglobinopathy screening, and quality control systems.

World leader and gold standard in delivering
high-quality HbA1c testing systems.

HbA1c results your clinicians can trust.

Our technology is backed by over 40 years of research in diabetes, hemoglobinopathies, and beta-thalassemia. Our HbA1c diagnostic tests are run on hemoglobin testing systems that are NGSP certified, IFCC traceable, and standardized to DCCT as recommended by the American Diabetes Association4. In fact, more NGSP-certified labs are powered by Bio-Rad ion-exchange HPLC than any other system or method. In addition, our assays are CE marked and FDA cleared.

More NGSP-certified labs5 are powered by Bio-Rad A1c

A1c methods adopted by NGSP L1&2 certified labs

The purpose of the NGSP is to standardize Hemoglobin A1c test results to those of the Diabetes Control and Complications Trial (DCCT) and United Kingdom Prospective Diabetes Study (UKPDS) which established the direct relationships between HbA1c levels and outcome risks in patients with diabetes.

  • NGSP certification requires optimal instrument performance
  • NGSP certification demonstrates DCCT and UKPDS traceability
  • 62% of total NGSP-certified labs* worldwide trust HPLC for A1c testing, out of which 63% trust Bio-Rad HPLC

Resources for Healthcare Providers and Patients

HbA1c Wallet Card

The American Diabetes Association (ADA) recommends using the HbA1c test to diagnose diabetes. Bio-Rad has created an HbA1c wallet card that lists glycemic ranges and frequency of testing to raise patient awareness. To help your patients meet their HbA1c goals, share our wallet card.

Download (EN)

Download (ES)

Download (PT)

HbA1c Wallet Card image

Keeping You Informed​

Proper screening, monitoring, and management of people with diabetes is important to slow the progress of the disease and limit complications. This brochure is aimed to help keep you and your patients up-to-date on HbA1c testing methods and ADA guidelines for managing diabetes. It also outlines the 2022 screening guidelines for diabetes.

Download pamphlet

Download poster



  1. Weykamp C (2013). HbA1c: A Review of Analytical and Clinical Aspects. Annals of Laboratory Medicine.
  2. Gore M, McGuire D, et al. (2016) A Test in Context. Journal of the American College of Cardiology., 68 (22) 2479–2486.
  3. Little RR et al. (2015). Effects of 49 Different Rare Hb Variants on HbA1c Measurement in Eight Methods. Journal of Diabetes Science and Technology I-8.
  4. U.K. Prospective Diabetes Study (UKPDS) Group (1998). Intensive blood-glucose control with sulphonylureas or insulin compared with conventional treatment and risk of complications in patients with type 2 diabetes (UKPDS 33). UK Prospective Diabetes Study (UKPDS) Group. Lancet 352:837-53.
  5. NGSP. (March 2021). List of NGSP Certified Laboratories.
  6. DCCT Research Group (1996). The absence of a glycemic threshold for the development of long-term complications: the perspective of the Diabetes Control and Complications Trial. Diabetes 45(10), 1289–1298.
  7. Nathan DM et al. (1993). The Effect of Intensive Treatment of Diabetes on the Development and Progression of Long-Term Complications in Insulin-Dependent Diabetes Mellitus. The New England Journal of Medicine 329(14), 977–986.
  8. American Diabetes Association (2020). Pharmacologic Approaches to Glycemic Treatment: Standards of Medical Care in Diabetes—2020. Diabetes Care 43(Supplement 1): S98-S110.