More specifically...
Uranium is a naturally occurring, heavy, metallic element that is found virtually everywhere in nature—in rocks, soil, plants, and our bodies. The average person ingests about 2 µg (around 1/15,000 of an ounce) of uranium in food and water every day, but only a very small fraction—on the order of 1 or 2 percent—is absorbed into the body. Thus almost all of the uranium we ingest is never absorbed but is excreted in the feces.
Of the small fraction of ingested uranium that is absorbed through the gut, most is quickly excreted in the urine and only a tiny amount is excreted in the hair. This is perfectly normal. The hair from different people—or even the same person—will contain varying amounts of uranium, depending on how much is in the water and food that people drink and eat. Some people might have ten or even hundreds of times the amount of uranium in their hair than do others.