The best method of accurately determining zinc status is through measuring white blood cell levels. Since this test is not readily available and may be more expensive, serum zinc is routinely used as a screening tool. Hair levels may show deficiencies or excesses but are generally not considered as reliable as other tests of zinc status. While low hair zinc is likely to be indicative of poor zinc status, elevated hair zinc may be indicative of low zinc in the cells or contamination from the use of zinc-containing shampoos. The zinc taste test appears to be of some value in determining general zinc status.