The reason for this is that many drugs, especially heroin, will remain in the hair for up to three months, according to ExpoMed. Generally, heroin can show up on a urine test for as little as two and half hours or as much as two days, according to MedlinePlus.However, heavy users can fail a drug urine test for as long as seven days.he reason for this is that many drugs, especially heroin, will remain in the hair for up to three months, according to ExpoMed. Generally, heroin can show up on a urine test for as little as two and half hours or as much as two days, according to MedlinePlus.