How Long Does Weed Stay in Your System?

Weed, also known as cannabis or marijuana, is one of the world’s most widely used recreational drugs. With its growing popularity, it is essential to understand its effects and potential impact on our physical and mental health. Despite its widespread use, there is still a lot of confusion regarding marijuana, from its effects on the body to how long it lasts in the body. Let’s explore the science behind how marijuana is metabolised, provide a comprehensive guide to how long it typically stays in the system, and give tips to reduce its use.

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What Makes up Weed?

Cannabis comprises hundreds of compounds. Still, the most well-known are cannabinoids, such as delta-9-tetrahydrocannabinol (THC) and cannabidiol (CBD). These compounds are responsible for the plant’s psychoactive and therapeutic effects. It also contains terpenes, which contribute to its unique aroma and flavour.

Legalising Marijuana for Medicinal Purposes

Cleansed versions of the oils or medicines produced by reliable institutions in countries where medical marijuana is legalised have mainly CBD without THC and will have different effects on your body. Still, in the United Kingdom, cannabis is considered a Class B drug and is completely illegal. This might be because of the negative statistics observed. From data in 2020, over 29.6% of people in England and Wales aged between 16 and 59 have used cannabis at least once. Consequently, deaths related to cannabis use in England and Wales amounted to 36, the highest annual amount in the last 25 years.

How Does Weed Get You High?

The psychoactive compound THC (delta-9-tetrahydrocannabinol), which we already mentioned, enters the bloodstream and binds to cannabinoid receptors in the brain and central nervous system. This process happens when smoked or otherwise consumed and causes altered perception, mood, and other cognitive and physiological processes, leading to feeling “high.”

In addition to the “high” feeling, marijuana use can also cause a range of other symptoms, including:

  • Altered perception of time
  • Changes in mood, such as increased euphoria or paranoia
  • Increased appetite
  • Dry mouth
  • Bloodshot eyes
  • Slowed reaction time
  • Impaired memory and concentration
  • Increased heart rate

The effects of marijuana can vary greatly depending on factors such as the strain’s potency, the method of consumption, and the individual’s tolerance, biology, and environment.

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How Long Does Weed Stay in the System?

Typically, marijuana can be detected in the urine for 3-30 days after use. In heavy, long-term users, it can be detected for several weeks. In blood, it can be detected for up to 72 hours, and in hair, it can be seen for up to 90 days. Remember that these are general estimates, and the specific length of time it stays in the system can vary significantly from person to person.

Detection Tests for Weed


Saliva testing for marijuana is a relatively new method for detecting recent drug use. Employers and law enforcement often use it for on-site or roadside testing. Saliva tests can detect THC in the oral fluid for up to 72 hours after use–this was confirmed based on a study in 2020. However, the accuracy of saliva tests can be influenced by factors such as the time of the last use and the individual’s metabolic rate.


Hair tests are considered more reliable than other drug testing methods, such as urine or blood tests, as they can detect long-term drug use (up to 90 days). In addition, THC and other drugs can become incorporated into the hair follicle as it grows, providing a longer detection window compared to other testing methods.


Blood serum and plasma tests measure the concentration of THC in the blood. They are commonly used in workplace drug testing and can detect THC within minutes to a few hours after use.

Factors That Affect How Long Weed Stays in Your System

The length of time marijuana stays in the system depends on several factors, including:

  1. Frequency and amount of use: The more you use marijuana, the longer it will take for weed to clear from your system.
  2. Body fat: THC in weed is fat-soluble and is stored in fat cells. So, individuals with higher body fat percentages will take longer to eliminate weed from their system.
  3. Metabolism: Weed is metabolised by the liver, so individuals with a faster metabolism will clear THC more quickly.
  4. Type of administration: Oral weed stays longer in the system than inhaled weed.
  5. Age: Older individuals tend to have a slower metabolism and may take longer to clear weed from their system.
  6. Hydration: Staying hydrated can help flush THC out of the system faster.
  7. Drug tolerance: Regular users of marijuana may build up a tolerance to THC and have higher levels of the substance in their system for more extended periods

Dangers of Using Weed

There are several potential dangers associated with using marijuana, including:

  1. Impaired judgment and coordination: THC can impair cognitive abilities and motor skills, making driving or operating heavy machinery while under the influence dangerous.
  2. Addiction: Regular use of marijuana can lead to the development of a substance use disorder, and withdrawal symptoms can occur when use is stopped.
  3. Mental health effects: Some individuals may experience anxiety, paranoia, or psychosis after using marijuana, particularly if they have a pre-existing mental health condition.
  4. Respiratory problems: Smoking marijuana can lead to respiratory problems, including bronchitis and lung infections.
  5. Long-term effects: Long-term use of marijuana can lead to decreased cognitive function, motivation, and educational and career achievement.

Tips to Detox from Weed

Considering the effects of consistent weed intake, it is essential to reduce our intake. Here are some steps to help detox from marijuana.

  1. Hydrate: Drinking plenty of water can help flush THC from your system.
  2. Exercise: Physical activity can help increase metabolism and release stored THC from fat cells.
  3. Healthy diet: Eating a diet rich in fruits, vegetables, and whole grains can support liver function and help clear THC.
  4. Set a goal: Determine why you want to reduce your use of marijuana and set a specific, achievable goal.
  5. Keep track: Keep a journal of when and how much marijuana you use, and identify patterns or triggers that lead to increased use.
  6. Find alternatives: Try to find alternative activities to replace the time spent using marijuana, such as exercise, hobbies, or spending time with friends and family.
  7. Gradually decrease use: Gradually reduce the marijuana you use each day rather than quitting abruptly.

Detoxing from marijuana is a process that varies for each individual, and some individuals may require additional support, such as medical supervision or rehabilitation. If you are struggling with substance use, it is recommended to seek help from a professional medical body. While outpatient detox is usually enough for marijuana addiction, The Providence Project’s residential programmes for drug addiction and dual diagnosis will be a better option for those who abuse more than one substance or are simultaneously treating a mental health condition.