Sickle cell trait test results
Sickle cell trait means a person has one copy of the sickle cell gene from one parent and a normal hemoglobin gene from the other. It is different from sickle cell disease, and it does not turn into it. (NHLBI, trait)
Trait or disease
- Sickle cell trait. One copy of the sickle cell gene. People with the trait are sometimes called carriers, and usually do not have symptoms of the disease. (NHLBI, trait) About 1 in 13 Black babies born in the United States have the trait. (NHLBI, trait)
- Sickle cell disease. Two copies of the sickle cell gene, or one copy of the gene for hemoglobin S and another for a different faulty hemoglobin. (NHLBI, trait) MedlinePlus says people with sickle cell trait do not have the symptoms of sickle cell disease. (MedlinePlus, sickle cell disease)
What each result means
| Result | What it means |
|---|---|
| Sickle cell test negative | No hemoglobin S was found. Iron deficiency or a blood transfusion in the past 3 months can cause a false negative. (MedlinePlus, sickle cell test) |
| Sickle cell test positive | Hemoglobin S was found. The person might have sickle cell disease or sickle cell trait. This test cannot tell the two apart, so hemoglobin electrophoresis is done next. (MedlinePlus, sickle cell test) |
| Hemoglobin test shows sickle cell trait | One sickle cell gene and one normal gene. Most people with sickle cell trait do not have health issues, but the sickle cell gene can be passed on to children. (MedlinePlus, electrophoresis test) |
| Hemoglobin test shows sickle cell disease | Two copies of the sickle cell gene, or one copy of the gene for hemoglobin S and one copy of a gene for a different faulty hemoglobin. (NHLBI, trait) |
| Newborn screen shows trait | Newborn screening programs also find out whether a baby has sickle cell trait. If so, genetic counseling will be offered. (NHLBI, diagnosis) |
In adults, MedlinePlus lists hemoglobin S as normally absent. (MedlinePlus, electrophoresis) To understand the result, your provider will consider your symptoms, medical history and other blood tests, such as a complete blood count. (MedlinePlus, electrophoresis test)
How the test is done
- The sample. In adults, a blood sample from a vein in the arm. In newborns, a few drops of blood from a heel prick. No special preparation is needed. (MedlinePlus, electrophoresis test)
- Sickle cell test. Also called Sickledex or Hgb S test. It shows whether hemoglobin S is present, but it does not tell trait from disease. (MedlinePlus, sickle cell test) The NCAA rule refers to a sickle cell solubility test. (NCAA)
- Hemoglobin electrophoresis. An electric current is applied to the blood sample, which separates the normal and abnormal types of hemoglobin so each can be measured. (MedlinePlus, electrophoresis test) A blood transfusion within 12 weeks can give false normal or abnormal results. (MedlinePlus, electrophoresis)
- Newborn screening labs. The most used tests are high-performance liquid chromatography (HPLC), capillary electrophoresis and isoelectric focusing. (NHLBI, diagnosis)
- Genetic testing. Can tell whether a person has one or two copies of the sickle cell gene, and can help confirm a diagnosis when blood test results are not clear. (NHLBI, diagnosis)
Why adults may not know their status
The NCAA says tests for sickle cell trait are done on all newborns in the United States, but few people are aware of a positive result because the condition is not considered life threatening in most of the population. (NCAA) NHLBI says to check with your child's healthcare provider to learn newborn screening results, and that adults have several options for getting tested. (NHLBI, trait) How newborn results are reported is covered on newborn screening results.
What trait means for future children
Sickle cell disease is inherited in an autosomal recessive pattern: both copies of the gene must have a variant to cause it, and the parents of a person with the disease each carry one copy, usually without signs of the condition. (MedlinePlus Genetics) ASH says that if both parents have sickle cell trait, their child has a 25% chance of having sickle cell disease; if only one parent has the trait, their child has a 50% chance of inheriting the trait but cannot get the disease. (ASH) Testing before and during pregnancy is covered on genetic carrier screening.
Trait and health
NHLBI says most people with sickle cell trait never have serious medical problems, but in rare cases some do. Symptoms are more likely when the body needs more oxygen than usual, such as with intense physical activity, activity at high elevations or in unpressurized airplanes, dehydration, or extreme heat or cold. Some people with the trait have damage to their kidneys or spleen. (NHLBI, trait) ASH says blood in the urine should be brought to a medical provider's attention, as it can rarely be a sign of a kidney cancer linked with the trait. (ASH) The ADA says people with sickle cell trait should have an A1C test done with a method that hemoglobin variants do not interfere with. (ADA, 2026)
The NCAA testing rule
A student-athlete must give their school documented results from a previous sickle cell solubility test, or be tested during the preparticipation medical exam. The NCAA says the purpose is to make coaches and athletic trainers aware that some athletes may need to take precautions, and that there is no reason student-athletes with sickle cell trait should not be allowed to compete. (NCAA)
When to contact a medical professional
The MedlinePlus Sickle cell disease page says to contact your health care provider if you have: (MedlinePlus, sickle cell disease)
- Any symptoms of infection (fever, body aches, headache, fatigue)
- Pain crises
- Painful and long-term erection (in men)
Where they differ:
- Testing athletes. The NCAA requires each student-athlete's trait status, from a test or a documented prior result. (NCAA) ASH says it urged athletic organizations to adopt universal preventive measures in training to protect all athletes, regardless of trait status. (ASH)
- Risk with heavy exercise. The NCAA says the trait can affect some athletes during periods of intense exercise. (NCAA) ASH says that rarely, extreme conditions such as severe dehydration and high-intensity activity can lead to serious health issues. (ASH) NHLBI says more recent studies in athletes and military recruits have shown that sickle cell trait is not associated with injuries in extreme heat or heavy exercise. (NHLBI, trait)
- Trait as a cause of death. The NCAA describes sudden deaths in athletes with sickle cell trait during conditioning sessions. (NCAA) ASH's January 2025 position statement says listing sickle cell trait as a cause of death on an autopsy report is medically inaccurate and without medical evidence of causation. (ASH) NHLBI says sickled cells found in the blood after death do not mean the person died from complications of sickled cells. (NHLBI, trait)
Your doctor decides what your result means for you.
Questions people ask
Can sickle cell trait turn into sickle cell disease?
No. NHLBI and ASH both say sickle cell trait does not turn into sickle cell disease. People with the disease have two copies of the sickle cell gene; people with the trait have one. (NHLBI, trait) (ASH)
Was I tested at birth?
Possibly. NHLBI says almost all newborns in the United States are screened for sickle cell disease, and that newborn screening programs also find out whether a baby has sickle cell trait. The NCAA says few people are aware of a positive result because the condition is not considered life threatening in most of the population. (NHLBI, diagnosis) (NCAA)
How can an adult find out?
NHLBI says adults have several options for getting tested and to ask your provider about it, especially if you are planning a pregnancy or are pregnant. The NHS says you can ask your GP about a blood test to check whether you are a carrier. (NHLBI, trait) (NHS, 2026)
Does sickle cell trait affect other blood tests?
It can affect the A1C test. The ADA says an A1C method without interference from hemoglobin variants should be used in people with sickle cell trait. (ADA, 2026)
Do NCAA athletes have to be tested?
The NCAA says a student-athlete must give their school documented results from a previous sickle cell solubility test, or be tested during the preparticipation medical exam. (NCAA)