Is there a Blood test for marijuana?

LENGTH OF TIME THC CAN BE DETECTED:

In Blood:

Frequent User: Delta-9-THC = 4-8 hours post dose, then possible "baseline" level of 0.3 to 0.4 ng/ml. 11-nor-9-carboxy-THC = approximately 2 weeks + depending on past frequency of use.

Infrequent User: Delta-9-THC = 3-4 hours post dose 11-nor-9-carboxy-delta-9-THC = 2 -3+ days post dose

In Urine:

Several days to 30 days average, seen up to 3 months on an extremely heavy user. THC is a lipid soluble drug, therefore stores in the fat in the body and the amount of time it takes to clear the system is dependent on how much drug was used and over what period of time the drug is used.

DURATION OF EFFECTS: Approximately 3 hours, peaking at 60 - 90 minutes post dose.