How long does weed stay in your system? What smokers should know this 4/20.

Corrections/clarifications: A previous version of this story incorrectly said women generally have less body fat than men.

As of April 2024, 24 of the 50 U.S. states, plus the District of Columbia, have fully legalized marijuana, with the other 26 range from mixed legality to full illegality. States like Idaho, Wyoming and South Carolina keep weed fully illegal, with criminal charges and zero medicinal use. California, New York and Michigan have completely legalized cannabis, along with decriminalizing it and enabling medicinal use.

New and veteran users may be wondering when it’s okay to drive or take a drug test after ingesting the drug by smoking or eating. Here's what we found out.

How long does weed stay in your system?

After weed enters your system, it can take between one to three hours to feel the complete effects and another one to three hours for those effects to wear off, according to Healthline. American Addiction Centers says, when eaten, the effects of weed edibles can last for multiple hours. Weed can be detected in your body for far longer after its effects wear off.

How long do tests detect weed?

Medical News Today says first-time smokers may have cannabis detected for “about 3 days,” while more consistent smokers at three to four times per week can have it detected for “5-7 days” afterward. Daily smokers can expect tests to detect weed for at least 30 days.

Specific tests include urine, saliva, hair and blood tests, says Medical News Today. Urine tests detect weed between three and 30 days. Saliva tests generally detect cannabis within 24 hours but have been known to detect cannabis for up to three days after use. Hair tests can detect cannabis for up to 90 days but can give false positives if the person being tested was recently in contact with a cannabis user. Blood tests detect weed for three to four hours.

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What influences how long tests detect weed?

Tetrahydrocannabinol (THC) is the chemical in weed that gives users the high that has made it popular. How long tests can detect weed is dependent upon how long it takes for your THC to metabolize, says Medical News Today.

Whether weed is detected depends on the THC dose, the person’s body fat, their sex, how hydrated they are, if they recently exercised and their metabolism rate.

The strength and quantity of the THC consumed can be the difference between a positive and negative test, as drug tests are searching for THC, not cannabis, says Medical News Today.

Those with higher body fat will metabolize weed slower than those with less fat, according to Medical News Today. Women generally have more body fat than men, lowering their metabolism rate. Hydrating more than normal won’t necessarily affect the results of a drug test, but dehydration may increase THC concentration. Regular exercise won’t change a drug test’s results, but exercising right before a drug test may increase the chance of a positive test. 

Those with faster metabolism rates will remove THC from the body quicker than those with slower metabolisms.

How to get weed out of your system

According to Healthline, you’re very limited in your options to metabolize weed out of your system at a faster rate. Exercising, although not right before a test, healthy eating and hydration can all help, but they won’t substantially change your THC levels.

The most influential factor in getting weed out of your system is time, Healthline says.

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