Conditions such as ovulation, pregnancy and hyperthyroidism may decrease basophil levels in the blood, according to Vanderbilt University Medical Center. A decreased percentage of basophils may also be caused by an acute infection, cancer or a severe injury, notes MedlinePlus.
The normal absolute range of basophils is between 190 and 200 cells per microliter of blood. Children between 2 and 10 years old have more basophils than adults, and children less than a year old typically have twice as many basophils than older children, explains Vanderbilt University Medical Center.
The normal percentage of basophils, as compared to other white blood cells, is between 0.5 and 1 percent, according to MedlinePlus. Basophils are one of five types of white blood cells found in humans, and basophils are the least-common white blood cell type. Neutrophils are the most common, and they account for 40 to 60 percent of all white blood cells at any given time. Lymphocytes are next at 20 to 40 percent.
Basophils are measured during a blood differential test, which is used to ascertain several conditions and disorders. Basophil levels may indicate a parasitic infection, an allergic reaction, chronic myeloid leukemia or myelodysplastic syndrome, notes Vanderbilt University Medical Center. Drugs and medications such as hydroxocobalamin may affect test results. Increased basophil counts may be caused by nephrosis, ulcerative colitis, hypothyroidism and splenectomy surgery.