The short answer to this question is “it varies.”
The duration wherein marijuana or weed can be detected in blood or urine will depend on when you last used cannabis, and how much cannabis you consumed.
On average, weed can be detected from a day to thirty days from the time that the cannabis was last consumed. Like other substances, however, weed can be detected in human hair for many months after last use.
What is the impact of dosing on detection times?
The frequency of use as well as the dosing has an impact on how much of the natural compounds and byproducts are left in your system. Generally speaking, the more frequently you use weed and the higher the dosing, the longer and more pronounced the byproducts are in your bloodstream, urine, and hair.
People who regularly use marijuana, either through ingestion, vaporizing, or smoking, often have the longest detection times. The record so far is three months after the person has last used cannabis.
In one study published by the Basel Proceedings, researcher Alain Verstraete points out that predicting the detection times of substances like weed is difficult because it relies on different factors, including the frequency of use, was there a full stop before and how long the full stop occurred, and other such factors.
Basically, detection times are determined by the level of consumption and lifestyle of the person. For cannabis, a dose of 34/SM yields the following results: THC remains detectable in blood serum levels after 36 hours at a level of 10 ng/mL, while THCCOOH remains detectable for up to 12 hours at a level of 10 ng/mL.
Understanding weed and drug tests
Common drug tests involve measuring the level of detectable metabolites of weed in urine and blood. Byproducts of weed can also be measured days after the person has consumed weed.
The duration of the psychological effects of weed has nothing to do with the duration that its metabolites stay in your system after consumption.
Weed window periods
The average window periods for different kinds of weed users are listed below. Take note that different drug tests have different window periods. The ones listed below are the average values for blood serum and urinalysis screening:
- If you are an occasional user who consumes weed no more than three times every seven days, the window period is three days.
- If you are a moderate weed user who consumes weed up to four times every seven days, your window period would be five to seven days.
- If you are a chronic user who consumes weed once a day every week, the window period is ten to fifteen days.
- And finally, if you use weed heavily and chronically, and you consume it more than once per day on a weekly basis, the window period is longest for you, at more than thirty days.
One of the reasons why cannabis byproducts and metabolites stay so long in the body is that they are fat-soluble.
What this means is after you consume the weed, these compounds have a tendency to bind to fat molecules in your body. This prolongs their stay in the body, before they are fully expelled by the liver and kidneys.