What is the difference between sickle cell trait and disease?

If you have the sickle cell trait, you do not have sickle cell disease. Having the trait means that you are a “carrier” of the sickle cell gene, but you do not have the condition itself ^[1][2].

Because sickle cell disease is a genetic condition, understanding the difference between the trait and the disease comes down to how many copies of the mutated gene you inherited from your biological parents.

The Genetic Difference

Genes come in pairs. You inherit one copy from your mother and one from your father. The genes responsible for sickle cell conditions control how your body makes hemoglobin—the protein in red blood cells that carries oxygen.

• Sickle Cell Trait: You have the trait if you inherit one normal hemoglobin gene from one parent and one sickle cell gene from the other parent ^[3]. Because you have one normal gene, your body still produces enough healthy hemoglobin to keep your red blood cells functioning normally.
• Sickle Cell Disease: You have the disease if you inherit two abnormal hemoglobin genes (one from each parent) ^[4]. Without a normal hemoglobin gene, your red blood cells can become hard, sticky, and C-shaped (sickled) ^[4].

(Note: The sickle cell trait is very common in certain populations worldwide because carrying one copy of the gene historically offered some protection against severe malaria ^[1].)

Symptoms: What to Expect

The day-to-day experience of someone with the trait is drastically different from someone with the disease.

• Sickle Cell Disease: People with the disease experience chronic health issues ^[4]. Because their sickled red blood cells die early and get stuck in blood vessels, they face a shortage of red blood cells (anemia) and episodes of severe pain known as pain crises ^[4]. Over time, this can lead to organ damage in the kidneys, liver, and eyes ^[5].
• Sickle Cell Trait: People with the trait usually live completely normal, healthy lives with no symptoms ^[6]. However, under extreme physical stress—such as severe dehydration, extreme military-style exercise, or being at very high altitudes—people with the trait have a slightly higher risk of muscle breakdown (exertional rhabdomyolysis) or kidney issues ^[7][8].
  • Staying Safe While Active: You can still exercise regularly! To protect yourself, simply stay well-hydrated, take breaks, and avoid pushing yourself to the point of absolute physical exhaustion ^[9][10].

Passing the Gene to Your Children

The most important reason to know if you have the sickle cell trait is for family planning ^[11]. Because you carry one sickle cell gene, you can pass that gene on to your children. In many countries like the US and UK, you may already know your status because most people are tested at birth via newborn screening ^[12].

Whether your child will have sickle cell disease depends entirely on the genetics of the other biological parent ^[13]:

• If the other parent has normal hemoglobin, your children cannot inherit sickle cell disease. Each child will have a 50% chance of inheriting the trait.
• If the other parent also has the sickle cell trait, each child has a 25% chance of being born with sickle cell disease, a 50% chance of having the trait, and a 25% chance of having neither ^[11].
• If the other parent has a different abnormal hemoglobin trait (such as Hemoglobin C or beta-thalassemia trait), this can also result in a form of sickle cell disease when combined with your sickle cell gene ^[14].

If you are planning to have children, it is highly recommended that both you and your partner get a blood test (called a hemoglobin electrophoresis) to find out your exact sickle cell status ^[15].