World Sickle Cell Day is observed annually on June 19th to raise awareness of sickle cell disease, a group of inherited red blood cell disorders that affect more than 100,000 people in the United States and 20 million people worldwide. For people with sickle cell disease, red blood cells are crescent or “sickle” shaped and do not bend or move easily, which can block blood flow to the rest of the body and cause repeated infections and episodes of pain.

Hemoglobinopathies (also called hemoglobin variants) are inherited red blood cell conditions that affect hemoglobin, the protein that carries oxygen through the body. One of the most common hemoglobinopathies is hemoglobin S, the sickle cell gene. In a severe form of sickle cell disease, sickle cell anemia, a patient inherits two genes for hemoglobin S. 

Patients can also inherit one sickle cell gene and have sickle cell trait, often with no signs or symptoms. This means that many patients are unaware they have sickle cell trait. It is also worth noting that certain populations are more likely to inherit sickle cell trait—about 1 in 13 African Americans and about 1 in 100 Hispanics/Latinos have sickle cell trait. 

Sickle Cell Hemoglobinopathies and the A1C Test

For patients who have the sickle cell gene or other hemoglobinopathies, some A1C testing methods for blood glucose may produce unreliable results. An A1C test with falsely high outcomes could lead to the prescription of more aggressive treatments, resulting in increased episodes of hypoglycemia. Conversely, falsely low outcomes could lead to the undertreatment of diabetes.

Laboratories use many different assay methods to measure A1C. Health care professionals should suspect the presence of a hemoglobinopathy when

• an A1C result is unexpected or at odds with other diabetes test results
• an A1C result is below 4 percent or above 15 percent
• the results of self-monitoring of blood glucose differ from A1C results
• a patient’s A1C result is significantly different from a previous A1C result, following a change in laboratory A1C methods

For more information about hemoglobinopathies and alternative tests to measure blood glucose levels, view NIDDK’s health information on Sickle Cell Trait & Other Hemoglobinopathies & Diabetes.

And to learn more about NIDDK Director Dr. Griffin P. Rodgers’ career researching blood conditions, including sickle cell, watch the videos below.