How long is THC detectable in blood?
Active THC is detectable in blood 3–12 hours after smoking and up to 24 hours after edibles. Heavy daily users may remain positive for several days. Switzerland enforces zero tolerance for drivers at 1.5 μg/L THC.
Key facts
- After smoking: 3–12 h
- After edibles: up to 24 h
- Daily use: 2–7 days
- Driving ban ≥ 1.5 μg/L
- THC-COOH lasts longer than THC
Detailed answer
Smoked THC peaks within minutes and drops sharply — occasional users usually fall below cut-off within 6–12 h. In daily users, redistribution from fat stores extends detection to 2–7 days. Edibles rise and fall slowly, detection up to 24 h. In Switzerland the road-traffic zero tolerance is 1.5 μg/L blood THC.