Hi. Great question; sorry the answer isn't simple.

The cannabis levels in bloods and urine will depend on how much you have smoked, how strong the cannabis is, how regularly you use cannabis and in what way you use it. Also it can be affected by your mood, metabolism and your size, age, and gender. So not so simple. For example, the cannabis metabolite Tetrahydrocannibidol (THC) is stored in fat cells and if an individual uses stored fat quickly, then the THC will be depleted at a faster rate than someone with a slow metabolism.

In general, blood tests will pick up recent use (up to 36 hours) while urine tests can detect cannabis for up to 3 months (again depending on all the factors described above).