How long does cannabis stay in your system?

According to the Irish National Drug and Alcohol Survey 2019-20, cannabis is the most used drug in Ireland, with 40.3% of respondents admitting they personally knew somebody who used cannabis.

In this article, we take a closer look at cannabis, how long the drug stays in your system, and the long-term effects of cannabis use.

What is cannabis?

Cannabis, also commonly referred to as weed, dope, marijuana or hash, is a plant-based drug derived from the Cannabis sativa or Cannabis indica plant.

It is extremely popular among recreational drug users and is often sold as a soft lump of dried brown or green herbs.

Skunk, a particularly potent strain of cannabis, is typically bright green in appearance, and covered in tiny crystals.

Another common form of cannabis is cannabidiol (CDB) or CBD oil – a light yellow or amber liquid that is sold online and in select shops.

Cannabis is most commonly inhaled (smoked or vaped), but some people also add it to food and drink products such as teas, sweets or cakes. Food and drink products containing cannabis are known as ‘cannabis edibles’ or ‘edibles’.

In Ireland, cannabis is controlled under the Misuse of Drugs Act 1977 and 1984. This means that it is an offence to have cannabis in your possession either for personal use, or with the intent to supply.

The penalty for cannabis possession can include a fine, prison sentence, or both. However, several factors will be considered for sentencing including the type, quantity, and total value of the drugs found.

What does cannabis do to you?

It is important to remember that drugs affect different people in different ways, so not everybody will have the same experience while using the same substances. Drugs can even affect the same person differently when taken at a different time.

Cannabis is classed as a psychoactive drug and can have different effects depending on the person taking it, their mood, how much cannabis they have taken, frequency of usage and how much tetrahydrocannabinol (THC) it contains: the main psychoactive compound found in cannabis.

When a person consumes cannabis, THC is released into the body, altering normal brain communication, and affecting thinking, memory, movement, pleasure, and concentration.

This is why some cannabis users feel more relaxed, others become giggly and chatty, and some people become confused, paranoid, and anxious.

Cannabis can also cause other physical side effects such as lethargy, drowsiness, and increased hunger. Mild hallucinations can also occur, as can sickness and nausea. 

How long does cannabis stay in your system?

When a person uses cannabis, a proportion of the drug and its metabolites are released into the bloodstream, with a small amount being excreted by the body in a variety of ways.

How long cannabis remains in the system and how quickly a person might feel the effects depends on several factors including how the drug was ingested, how often it is used, and the metabolism and weight of the individual.

For example, when smoked, the effects of cannabis can be felt in as little as 60 seconds. When eaten, its effects can be felt in up to 45 minutes and can last for 2-4 hours.

It is important to note that when taken in large quantities, it can take days for a person to feel normal again after consuming cannabis. 

Is cannabis addictive?

Yes, cannabis is addictive. People who use cannabis regularly may experience cravings and withdrawal symptoms when they stop using it, leading to the development of harmful addictions.

When an individual ingests cannabis, either through smoking, vaping, or eating it, this alters the way the brain works and causes it to release dopamine.

Dopamine, the brain’s ‘feel-good’ chemical, creates feelings of euphoria, pleasure, and reward. These powerful sensations cause some people to become addicted and dependent on cannabis.

People who use cannabis on a regular basis are also more likely to build up a tolerance to it. This means that they will require even more of the drug over time to experience the same ‘high’.

How long does it take for cannabis to show up in a drug test?

Even after the ‘high’ has worn off, and long after the drug was first consumed, cannabis use can be detected by a drug test, depending on the type of test you take.

Oral fluid (saliva) tests can detect cannabis for up to 48 hours, while urine drug tests can detect a single-use of cannabis for up to four days after it has been consumed.

Chronic heavy use of cannabis can be detected up to 30 days after being ingested using the same urine drug testing methods.

The rate at which head hair grows means that head hair tests provide a wide window of detection for cannabis use, making it possible to detect concentrations of THC in the body for up to 12 months, depending on the length of the hair.

Similarly, nail drug testing can be used to provide an overview of up to 12 months for drug use (six months for fingernails and 12 months for toenails). 

What factors affect how long cannabis stays in your system?

How long cannabis remains in a person’s system depends on several factors including:

  • How much of the drug was consumed
  • Frequency of consumption
  • The person’s body mass index (BMI), weight and metabolism
  • The method of consumption (e.g. smoked, vaped, eaten)

What are the long-term effects of cannabis use?

Although the effects of cannabis can wear off in as little as an hour, depending on how much was consumed, regular cannabis use over a prolonged period has been linked to several long-term psychological and physical problems, including:

  • Breathing issues
  • Coughing
  • Increased heart rate and blood pressure
  • Fertility concerns
  • Anxiety, paranoia, and mood swings
  • Difficulty sleeping
  • Poor mental health episodes including schizophrenia

How can I find out if a loved one is using cannabis?

Our Home Drug Testing Kit has been designed to give you peace of mind or enable you to seek support for a friend or loved one who is struggling with substance misuse.

This easy-to-use, self-contained screening kit can detect drugs and their metabolites in a urine sample, with built-in test strips that allow you to read the results in just 5 minutes

Please be aware that our home drug test kits are for peace of mind only, and the results cannot be used in court. If you require a drug test for official matters, you will need a legally-instructed drug test.

For confidential advice about which test might best suit your needs, you can also call our Customer Services team on 01 402 9366 or email

Home Drug Testing Kit

Buy your easy-to-use home drug test kit online now for just €20.

Gail Evans AlphaBiolabs

Gail Evans

Technical Trainer at AlphaBiolabs

A professionally-trained forensic scientist, Gail joined AlphaBiolabs in 2012 and holds the role of Technical Trainer.

Her day-to-day responsibilities include delivering in-depth training sessions both internally and externally, covering DNA, drug, and alcohol testing.

Throughout her career at AlphaBiolabs, Gail has held a variety of roles, including within the Legal and Workplace sectors of the business.

Before joining the company, Gail was a practicing forensic scientist with 25 years’ experience working for the Forensic Science Service, attending scenes of crime, and analysing physical and biological material with potential evidential value.

Gail also holds qualifications in chemistry and is a Lead Auditor for the ISO 9001 standard, the international standard for quality management.

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