How Long Do The Effects Of Medical Cannabis Last?

Alternaleaf Team
Written by
Alternaleaf Team
Nov 20, 2023
Last updated:
May 2, 2024

Medical cannabis affects everyone differently, but it can be helpful to have a general idea of what to expect and how long the effects can last. While there are no hard and fast rules when it comes to duration or how powerful the effects might be, it’s still important to understand how your medicine works so you can approach it sensibly and better understand your treatment plan.

What Causes The Psychoactive Effects Of Cannabis?

Tetrahydrocannabinol (THC) is the compound in cannabis that causes its psychoactive effects (commonly known as a ‘high’), and is one of the two major cannabinoids in the plant, alongside cannabidiol (CBD). CBD is a non-psychoactive compound, meaning it has no effect on your mental or psychological functions.

Consuming medical cannabis introduces these so-called “phytocannabinoids” into our system, but our body also produces natural endocannabinoids – such as anandamide – which are molecules that bind to our cannabinoid receptors just like phytocannabinoids.

Phytocannabinoids and endocannabinoids both affect your endocannabinoid system, a complex cell-signalling network that consists of CB1 and CB2 receptors throughout the body.

The endocannabinoid system helps regulate a variety of bodily functions, including pain sensation, mood and appetite. It’s through affecting the endocannabinoid system’s receptors in the brain that THC creates its psychoactive effects.  

The experience of these effects can differ depending on several factors, but generally you can expect to feel relaxation, an increased appetite and mood changes. A cannabis high can also lead to anxiety or paranoia, particularly if a person takes too much THC or is inexperienced.

Does Ingesting Medical Cannabis Make The Effects Last Longer?

Ingesting medical cannabis instead of inhaling it will result in longer symptom relief. Ingestion means consuming capsules, oils or tinctures, while inhalation refers to either inhaling the dried cannabis flower using a dried herb vaporizer or vaping a cannabis cartridge.

When you inhale medical cannabis, the active compounds enter the lungs where they are quickly absorbed into the bloodstream. This is why inhalation causes a near instant effect, as the THC enters the system rapidly. You can expect the effects to peak at around 10 minutes and to last for 1 to 3 hours, although they can linger for up to 8 hours.

Ingestion is a much slower process. When you ingest cannabis products your liver must first break down the medication before the THC enters your bloodstream. This means that the effects will usually take around 30-60 minutes to appear, or sometimes up to 2 hours. Usually the effects will peak at around four hours and can last up to 12. You may feel the residual effects from an ingested cannabis product for up to 24 hours.

What Other Factors Affect How Long The Effects Of Cannabis Last?

Many factors contribute to the speed at which cannabis is absorbed. Since THC is fat-soluble, if you consumed food with a high fat content before consuming medical cannabis, THC’s effects may appear sooner and potentially last longer.

The speed of an individual's metabolism can also affect how your body processes THC. Your metabolism is influenced by several factors, including your age, weight, genetics and overall health. If you have a slow metabolism, your body may take longer to process THC, causing its effects to potentially last longer. The opposite of this may also be true: a faster metabolism may produce shorter but more pronounced effects.

If you’re prescribed a strain of medical cannabis that is high in THC, you may find that the effects last longer or are more intense. During your consultation, you and your doctor will discuss your condition and decide on a product with the appropriate amount of THC.=

Finally, your previous experience with cannabis can affect how your body processes THC. Tolerance to THC can build up with repeated use, meaning the effects of medical cannabis may be less pronounced or shorter in duration if you’ve been using it frequently.

How Long Does THC Stay In Your System?

Once THC is in your bloodstream, it passes into your liver where it’s metabolised into the compound that causes the psychoactive effects: 11-OH-THC.

11-OH-THC is then converted into an inactive compound called THC-COOH. This inactive compound is stored in your fatty tissue and gradually released into your bloodstream over days or weeks. It’s then eventually excreted as waste.

THC can remain in your system long after its effects have worn off. Australia has strict laws around driving and medical cannabis – you can’t have any THC detectable in your system while driving, even if you’re not experiencing any psychoactive effects. The only exception to this rule is in Tasmania, where if you have a medical cannabis prescription and have used your medication accordingly you may drive with small amounts of THC in your system, provided you are not impaired.

Due to the different variables influencing the speed at which cannabis is metabolised, there are no reliable time frames for when your system will be free of THC. We recommend finding alternative forms of transport while using medical cannabis. Some workplaces also conduct drug testing for THC, so make sure you know your workplace’s policies on medical cannabis before you get a prescription.

Can You Shorten How Long The Effects Of Cannabis Last?

There aren’t any ways to significantly shorten the duration of cannabis’ effects. Sleep may help to reduce the effects of cannabis. Your body will process and eliminate some of the THC from your system while you sleep and you’ll likely wake feeling refreshed.

If you are prescribed a CBD product, you may find taking your it helps to counteract the negative effects of THC. There’s some evidence that CBD acts as a modulator to THC, meaning it may reduce some of its less desirable effects such as anxiety and drowsiness).

Keeping hydrated will help speed up your body’s natural detoxification process, meaning some cannabis compounds may exit your system faster. Water can also reduce uncomfortable side effects such as dry mouth.

Working With Your Doctor to Ensure The Best Experience Possible

Everyone's system reacts differently to medications such as medical cannabis. Your age, gender, diet, health and previous cannabis use can change how your body reacts to cannabis and how long the effects will last.


Always follow your prescribed dosage instructions and discuss any questions or concerns with your prescribing doctor. Following your doctor’s recommendations will reduce negative side effects and help your Doctor to determine the efficacy of your regime.