A sickle cell test is a simple blood test used to determine if you have sickle cell disease or sickle cell trait. Sickle cell disease (SCD) is a group of inherited red blood cell disorders. People with this disease have red blood cells that are shaped abnormally. Instead of looking like doughnuts like normal red blood cells, they’re shaped like a crescent moon. The disease is named for the C-shaped farm tool known as a sickle.

Sickle cells often become hard and sticky, which can increase the risk of blood clots. They also tend to die off early. This causes a constant shortage of red blood cells.

People with sickle cell trait are genetic carriers of sickle cell disease. They have no symptoms and can’t develop sickle cell disease, but they may be able to pass it on to their children. Those with the trait may have a higher risk of some other complications, including unexpected exercise-related death.

The sickle cell test is part of the routine screenings performed on a baby after it’s born, but it can be used on older children and adults when needed.

Newborns are regularly screened for SCD soon after birth. Early diagnosis is key, because children with SCD may be more vulnerable to serious infections within weeks of birth. Testing early helps ensure infants with sickle cell get the proper treatment to protect their health.

Other people who should get tested include:

  • immigrants who haven’t been tested in their home countries
  • children who move from one state to another and haven’t been tested
  • anyone displaying symptoms of the disease

According to the Centers for Disease Control and Prevention, SCD affects an estimated 90,000 to 100,000 Americans. The disease causes the following symptoms:

  • anemia (which causes fatigue)
  • paleness and shortness of breath
  • yellowing of the skin and eyes
  • periodic episodes of pain (caused by blocked bloodflow)
  • hand-foot syndrome (swollen hands and feet)
  • frequent infections
  • delayed growth
  • vision problems

Your doctor will need a blood sample to test you for SCD.

A nurse or lab technician will place an elastic band around your upper arm to make the vein swell with blood. Then, they’ll gently insert a needle into the vein. The blood will naturally flow into the tube attached to the needle. When there’s enough blood for the test, the nurse or lab tech will take the needle out and cover the puncture wound with a bandage.

When infants or very young children are tested, the nurse or lab tech may use a sharp tool called a lancet to puncture skin on the heel or finger. Then they’ll collect the blood on a slide or test strip.

The sickle cell test is a normal blood test. Complications are extremely rare. You may feel a little lightheaded or dizzy after the test, but these symptoms will go away if you sit down for a few minutes. Eating a snack may also help.

The puncture wound has a slim chance of becoming infected, but the alcohol swab used prior to the test normally prevents this. Apply a warm compress to the injection site if you develop a bruise.

The lab tech who examines your blood sample will be looking for an abnormal form of hemoglobin called hemoglobin S. Regular hemoglobin is a protein carried by red blood cells. It picks up oxygen in the lungs and delivers it to other tissues and organs throughout your body.

Like all proteins, the "blueprint" for hemoglobin exists in your DNA, the material that makes up your genes. If one of the genes is altered or mutated, it can change how the hemoglobin behaves. Such mutated or abnormal hemoglobin can create red blood cells that are sickle-shaped, leading to SCD.

A sickle cell test looks only for the presence of hemoglobin S, which causes SCD. A negative test is normal. It means your hemoglobin is normal. A positive test result may mean you have sickle cell trait or SCD.

If the test is positive, your doctor will probably order a second test called hemoglobin electrophoresis. This will help determine which condition you have. If the test shows you have two abnormal hemoglobin genes, you’ll likely be diagnosed with sickle cell disease. If the test shows you have only one of these abnormal genes and no symptoms, you’ll likely be diagnosed with having sickle cell trait.

After the test, you’ll be able to drive yourself home and do all of your normal daily activities.

Your doctor will go over your test results with you. If the test shows you have the sickle cell trait, they may order more tests before they give you a diagnosis.

If you’re diagnosed with SCD, your doctor will work with you to develop a treatment plan that works for you.