Sickle cell test

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The sickle cell test looks for the abnormal

in the blood that causes the disease .

Alternative Names

Sickledex; Hgb S test

How the Test is Performed

A blood sample is needed.

How the Test will Feel

When the needle is inserted to draw blood, some people feel moderate pain. Others feel only a prick or stinging. Afterward, there may be some throbbing or a bruise. This soon goes away.

Why the Test is Performed

This test is done to tell if a person has abnormal hemoglobin that causes sickle cell disease and sickle cell trait. Hemoglobin is a protein in red blood cells that carries oxygen.

In sickle cell disease, a person has two abnormal hemoglobin S genes. A person with sickle cell trait has only one of these abnormal genes and no symptoms, or only mild ones.

This test does not tell the difference between these two conditions. Another test, called hemoglobin electrophoresis, will be done to tell which condition someone has.

Normal Results

A normal test result is called a negative result.

Normal value ranges may vary slightly among different laboratories. Some labs use different measurements or test different samples. Talk to your health care provider about the meaning of your specific test results.

What Abnormal Results Mean

An abnormal test result indicates the person might have one of these:

  • Sickle cell anemia
  • Sickle cell trait

Iron deficiency or blood transfusions within the past 3 months can cause a "false negative" result. This means the person might have the abnormal hemoglobin for sickle cell, but these other factors are making their test results appear negative (normal).


Veins and arteries vary in size from one person to another, and from one side of the body to the other. Obtaining a blood sample from some people may be more difficult than from others.

Other risks associated with having blood drawn are slight, but may include:

  • Excessive bleeding
  • Fainting or feeling lightheaded
  • Hematoma (blood buildup under the skin)
  • Infection (a slight risk any time the skin is broken)


Steinberg MH. Sickle cell disease and associated hemoglobinopathies. In: Goldman L, Schafer AI, eds. Goldman's Cecil Medicine. 25th ed. Philadelphia, PA: Elsevier Saunders; 2016:chap 163.

Wetzler M, Cornett PA. Hematology. In: Bope ET, Kellerman RD, eds. Conn's Current Therapy 2016. Philadelphia, PA: Elsevier Saunders; 2016:chap 12.

Version Info

  • Last reviewed on 2/11/2016
  • Todd Gersten, MD, Hematology/Oncology, Florida Cancer Specialists & Research Institute, Wellington, FL. Review provided by VeriMed Healthcare Network. Also reviewed by David Zieve, MD, MHA, Isla Ogilvie, PhD, and the A.D.A.M. Editorial team.

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