Heroin itself clears from the blood very rapidly — within 6 hours. However, heroin metabolises into morphine, which is detectable in urine for 2–4 days after use (up to 7 days for heavy users). Hair follicle tests can detect heroin use for up to 90 days. Heroin is typically detectable by standard UK drug tests for 2–3 days after a single use.
Estimates only. Individual results vary based on metabolism, body weight, hydration, and frequency of use.