In Opposite of Always, protagonist Jack King falls in love with Kate, but her experience with sickle cell disease, a condition sometimes referred to as sickle cell, complicates their relationship. Kate’s description of her symptoms aligns specifically with sickle cell anemia, which is “one of a group of inherited disorders known as sickle cell disease” (“Sickle Cell Anemia.” Mayo Clinic, 22 Dec 2023). A change in the gene that governs the body’s production of hemoglobin causes this disorder. Hemoglobin is a compound in red blood cells that allows them to deliver oxygen throughout the body. Sickle cell anemia affects the shape of red blood cells, which are usually round and flexible. It causes some of them to be shaped like crescent moons, or sickles. These cells slow or block the flow of blood in the body as they become rigid and sticky.

People who have sickle cell anemia experience significant symptoms. Anemia refers to a shortage of red blood cells, which occurs because sickle cells usually die in 10 to 20 days, unlike healthy red blood cells, which live for about 120 days. With this shortage, the body doesn’t get enough oxygen, leading to fatigue and other major problems.