Renal excretion accounts for most uranium (U) that is excreted from the body. Uranium is considered mildly toxic for two reasons, low-level radioactivity and moderate biochemical toxicity.

Uranium is a radioactive element with 10 isotopes with half lives exceeding one hour. U238 constitutes about 99% of the naturally- occurring U and this is the isotope measured at DDI and reported for this individual. U238 has a half-life of 4.5 X 10 to the ninth years. It decays by alpha emission to produce thorium, Th234, the initial step in a decay chain that eventually leads to lead. Alpha, beta and gamma emissions occur during this decay process. Because of the very long half-life, the radioactivity danger is only slight. However, exposure to enriched or nuclear fuel grade U (high in U235) does pose a health hazard. The measured result (U238) does not reflect or imply exposure to enriched U235.

The toxochemical effects of U may be more severe than the radiochemical effects for U238. Uranium has four valences (3,4,5 or 6), can combine with phosphate, citrate, pyruvate, malate, lactate, etc. in body tissues, and usually is transported in the blood as a carbonate complex. Uranium that is not excreted in urine can accumulate in bone and kidney tissues as well as in the spleen and liver. In excessive amounts, it can be nephrotoxic. Inhaled U accumulatesin lung tissue. Fatigue is the most common symptom associated with chronic, low-level (natural) U exposure (DDI observations).

Uranium is more common than mercury, silver or cadmium in the earth's rock strata, and may be present, at low levels, in ground (drinking) water. Most commercial use of U is for nuclear fuel, but it may be present in ceramics or colored glass, especially ancient or antique, yellow-colored glassware.

Hair elements analysis may provide further information regarding temporal exposure to U.

Whole blood U analysis may provide confirmation of very recent or ongoing exposure to uranium.