How Long Does Cannabis Stay In Your Bloodstream?

Have you ever been ordered to submit to a health screen? Perhaps it caused you to worry about not passing the test. Even though the active effects of cannabis wear off after a few hours, how long is it detectable? The answer is a little complicated.

Cannabis is metabolized very differently from person to person. Consumption frequency, method, and amounts are some of the more obvious variables that can affect cannabis blood testing, but age, gender, and body fat percentage can also affect results. Due to the many variables affecting detectable THC in the bloodstream, rough estimates of detection time windows are the best that current research can provide.

What about frequency and dosage?

Light: Occasional cannabis use, fewer than one to three times per week, in small amounts

Regular: Five to seven times per week with moderate dosages

Chronic: Daily cannabis use, frequently throughout the day or in large amounts, seven days per week

THC and its metabolite, THC-COOH, are the substances that drug tests seek. These substances are lipid-soluble, so overweight people will have THC in their system longer than those who have less body fat. Exercise breaks down fat and can release THC and THC-COOH back into the bloodstream, especially for overweight and chronic cannabis users. Unfortunately, THC released from exercise won’t get you high; levels are detectable but minuscule, so any post-exercise high likely is stemming from natural endocannabinoids and endorphins.

In general, regular, chronic, and overweight users will see THC and THC-COOH in higher levels on blood tests than light users. For light cannabis users, blood tests can generally detect THC and THC-COOH for up to 24-72 hours. For regular users and chronic users, expect to find detectable THC as long as three to seven days after your last consumption. According to LabCorp, operator of one of the world’s largest laboratory networks, “Testing can indicate use anywhere from three days to more than 30 days prior to testing. Chronic, heavy users of marijuana may test positive for even longer than 30 days after last use.” As exercise can re-release these compounds, avoid exercise for up to 72 hours prior to testing if you are an overweight or chronic user, as this can increase the odds of failing a blood test—even if you have not consumed cannabis in several weeks. As a rule, cannabis users with a higher body fat content will be on the high end of estimates for detectable metabolites.

Blood tests are increasing in popularity as a way to test for THC, especially because it does not typically detect THC as sensitively as a urinalysis, meaning it can provide a more accurate estimate of use in the last 30 days. Saliva tests detect as recently as 72 hours and may be a better indicator of cannabis use than blood tests for employment screenings or roadside testing. According to LabCorp, “Since screening tests are not definitive, confirmatory testing is typically done to verify the results. A positive confirmatory test means the person had THC or THC-COOH in their body when the sample was collected, but it does not confirm when THC was used or ingested.”

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