Metabolites are byproducts created when the body metabolizes an ingested drug. Every person metabolizes drugs in a similar fashion, making metabolites a predictable and reliable indicator that a certain "parent" drug has been used by the patient. Because metabolites stay in the body much longer than their parent counterparts, drug use is more accurately assessed by measuring metabolites rather than the parent drugs themselves. Testing for metabolites can also help eliminate test tampering and manipulation. If the parent drug is present in higher concentrations while the metabolites are present in much lower concentrations, it becomes apparent that a sample has been adulterated.