Blood disorders can affect any of the three main components of blood:

Red blood cells, which carry oxygen to the body's tissues

White blood cells, which fight infections

Platelets, which help blood to clot

Blood disorders can also affect the liquid portion of blood, called plasma. Treatments and prognosis for blood diseases vary, depending on the blood condition and its severity.

Most blood disorders decrease the number of cells, proteins, platelets, or nutrients in the blood, or interfere with their function. A majority of blood disorders are caused by mutations in parts of specific genes and can be passed down in families. Some medical conditions, medications, and lifestyle factors can also cause blood disorders to develop.