How long does THC stay in your system?

Liz Filmer
04 Sep 2023

How long it takes for the THC in cannabis to enter the system and produce effects depends on how potent the strain is, whether you smoke or consume edibles and how high your tolerance is. 

The results of smoking or vaping cannabis can be felt in two to 10 minutes and last for two to eight hours. Ingesting takes a bit longer due to the digestive processes, so that it could kick in anywhere from 30 minutes to an hour (sometimes up to two) and last for three to nine hours.

There are several ways to test for THC and its by-products: blood, saliva, urine and hair. Each can present chemicals for differing periods.

Blood Testing

Blood testing for THC from cannabis has the smallest window of time for accuracy, especially if you smoke it. However, traces of THC will hang around longer if you ingest it.

When it comes to smoking, THC levels will peak within three to 10 minutes. The speed at which it decreases will depend on how much you smoke and your body’s makeup. Still, the generally accepted time frame for THC detection in the blood is three to four 4 hours. 

Edibles, on the other hand, hang around in the blood for one to two days. This is because edibles need to be processed through the digestive system, which takes longer to process the marijuana metabolites.

Saliva Testing

THC and metabolites can appear in oral fluid by “passive diffusion” and are deposited in the mouth when smoked. A saliva drug testing kit uses a biochemical process known as enzyme immunoassay to detect THC. 

A recent study found that saliva testing can detect weed in the system up to 72 hours after use. For a frequent or heavy user, that number can double. However, roadside saliva tests can only detect THC for around 12 hours after use in infrequent users and 30 hours for people who use it frequently.

Saliva testing has become one of the most commonly used methods because it can detect weed use minutes or hours after smoking. However, recent studies suggest they are inconsistent and can produce false positives regularly.

Urine Testing

When you ingest cannabis, the liver breaks it down into metabolites. Twenty per cent of those leave the body through urine. On average, a pee test can detect THC between three and seven days. 

However, this changes depending on how regularly you smoke or ingest it. For those who use cannabis at least once a day, THC can be detected anywhere from 14 to 90 days from use. For a moderate user (three times a week), it may be detectable from five to seven days. For a one-time user, it’s one to three days.

THC can stay in the system of chronic users for so long because it builds up in the body and can only break down at a specific rate relative to your genetics. The extra THC will be stored in your fat cells and be slowly released.

Hair Testing

Depending on how long the hair is, it can range from one week to one year. But, like always, results heavily rely on the dose of cannabis ingested or smoked. 

When you ingest or smoke weed, THC will enter the bloodstream, bind to cannabinoid receptors in the body’s cells and bind to them. On the way, a few will enter the blood vessels that feed the cells in the scalp. Through the hair papilla, THC enters the area where the hair grows and sprouts upwards from the root, carrying THC into the hair follicle matrix. Interesting fact: the more pigmented the hair, the more a drug will bind to it – sorry, fellow brunettes. 

Can you do anything to get THC out of your system quicker?

There is a general lack of resources behind whether there is any way to detox or metabolise THC in the body quickly. However, some reports will tell you drinking lots of water, exercising (because a lack of fat cells means less storage for cannabinoids) and taking various detox agents could help if you have a drug test coming up. 

Some products on the market are designed to help cheat drug tests, but there is little evidence to show that they are reliable. There are ways to cheat urine drug screens, but most screening programs are wise to these.

Absence, regular exercise and a healthy diet are the only ways to help remove THC over time. It also relies on your body’s metabolic rate. So, all in all, there is no scientifically proven same-day detox method – sorry.

More on this topic from Soft Secrets:

Crackdown on recreational users

Government Urged to rethink drug strategy


Liz Filmer