All drug use has risks. This page is for information only and does not constitute or replace medical advice. If you have medical concerns about your drug use, please speak to a medical professional.
Cannabis leaf

Cannabis comes from the cannabis plant and is the most commonly used illegal drug in the UK. The main psychoactive ingredient is THC (tetrahydrocannabinol) which gives you the stoned feeling. Other ingredients include CBD and plants may be grown to contain different amounts of THC or CBD and can give different effects. Plant varieties can be bred to produce stronger hybrid strains.

Cannabis should not be confused with "synthetic cannabinoids" also known as "Spice".

Other names

weed, ganja, green, grass, pot, bud, hash, resin, shatter, edibles, pollen, squidgy black, soapbar, skunk


Herbal cannabis appears as dried plant leaves or buds in brown/green shades; resin appears as compressed blocks in shades of brown; oils may vary in consistency or thickness and may be amber, gold or dark brown. Oils may be sold in droppers, syringes or capsules.

Drugs Wheel Category



Misuse of Drugs Act (1971) – Class B.

Cannabis oils containing more than 0.2% THC are illegal to possess, sell, buy or give away.
Penalties for possession are up to five years in prison and/or an unlimited fine. Penalties for supply are up to 14 years in prison and/or an unlimited fine.

How it’s taken

Cannabis may be smoked in a joint, bong or pipe, or vaporised. It may also be found in edible items such as butter, cookies, chocolate, fudge or sweets. In oil form it may be absorbed under the tongue or swallowed in a capsule. There is also a method of heating oils to a high temperature and inhaling the smoke called “dabbing”. Oil extracted from cannabis plants can contain varying amounts of THC and CBD. Some may contain very low levels of THC and will not produce a psychoactive effect or very high levels of THC and be much stronger than herbal cannabis.


People using cannabis have reported the following dose/duration of effects, but this cannot be taken as a recommendation: duration and effects of any drug will depend on purity, regularity of use, other medications or drugs you have taken, your body and how it’s taken.

Many people may find that 25mg of cannabis will give them an effect if smoked or vaped. If swallowed or eaten the effects can be felt more strongly from smaller amounts and 5-10mg may produce an effect.

General information on dosing.


The onset of effects will vary depending on the route of administration. When cannabis is smoked or vaped the onset of effects can be felt within 10 minutes and may last for up to four hours.  Smoking in a bong, pipe or vape may cause the effects to be felt more quickly than if smoked in a joint.

Cannabis that is eaten in food will take longer to have an effect – up to two hours and the effects could last longer – up to six hours.

Cannabis can make you feel happy, relaxed, calm and giggly. Other effects can include feeling hungry, withdrawn, tired and paranoid. It can also cause dizziness and sickness (also known as a “whitey”) especially when used in conjunction with alcohol.

A higher THC content may produce a more energising experience while higher CBD content may produce a more relaxing experience. Cannabis is used medicinally by some people and the licensing of medicinal cannabis in the UK is currently under review and development.

It can cause dry mouth, red eyes, changes in blood pressure and blood sugar levels and some people may feel like their heart racing.

The effects may vary based on your mood and environment (also known as set and setting).


Mixing with tobacco puts you at risk of nicotine addiction, and all the harms to the lungs and heart of smoking

Remember nicotine is a stimulant drug and can contribute to poor mental health

Be aware resins (soapbar) can contain henna, plastic and other fillers

Cannabis can affect your short-term memory (while using cannabis)

People with existing mental health issues may want to avoid cannabis as some people can be more vulnerable to the potential negative effects of cannabis

Increasing tolerance (needing more cannabis to feel the same effect as before) can be a sign of dependency. Check out your use here.

There is a risk to an unborn child if used during pregnancy



Harm reduction

If you choose to take cannabis then the following steps can help to reduce harm.
  • If smoking, try to use unprinted card for roaches so you don’t inhale ink chemicals.
  • Better yet – ditch tobacco!
  • Avoid holding smoke in your lungs – this won’t increase the high but will cause more damage to your lungs
  • Clean all pipes/bongs regularly
  • You can’t judge an accurate dose by looking – start low and go slow
  • When eaten it can be easier to take too much and risk a “whitey” (feeling sick, sweaty and possibly anxious) – remember you can’t take less once you have swallowed it!
  • Avoid mixing with alcohol and other drugs. Mixing drugs can lead to unexpected and unpredictable effects
  • If you do feel any negative effects remember that these will pass – telling a friend and changing your environment may help ease these feelings
  • Think about taking a  “T-break” every once in a while (‘T’ standing for tolerance). Worried about your use of cannabis? Use our Check-it out tool here

Detection time

People taking cannabis have reported the following detection time, but this cannot be taken as a recommendation; detection of any drug will depend on purity, regularity of use, other medications or drugs you have taken, your body and how it’s taken.
  • 3-20 days or up to 12 weeks with long-term use