11 min read
Sam North
How long does cannabis stay in your system? THC can remain detectable in saliva tests for 24-72 hours, urine tests up to 30 days, blood tests for 24 hours, and hair tests up to 90 days
The length of time THC will stay detectable in your system depends on the type of test you take.
Saliva tests, the most common form of roadside testing, may detect traces of THC between 24 and 72 hours after you have last taken your medical cannabis. Blood tests can pick up THC for a shorter window of around 24 hours, though this may also extend out to three days for patients who medicate frequently. Urine tests, the most common drug screening method, can detect THC metabolites anywhere from 3 days after a single dose, but for patients who take medical cannabis regularly, this window can extend out to 30 days. Hair tests typically analyse the 1.5 inches or so closest to the scalp, which reflects around 90 days of growth, so they can show THC consumption up to 90 after a patient last took their medication.
Key takeaways
Contents
|
Test type |
Detection window |
|
Saliva |
Between 24 and 72 hours |
|
Blood |
24 hours, up to three days for patients who medicate frequently |
|
Urine |
Around three days for patients who medicate irregularly, up to 30 days for patients who take medical cannabis daily |
|
Hair |
Up to 90 days |
Cannabis will typically stay detectable in a saliva test for between 24 and 72 hours, depending on how much you took, the potency, and how frequently you take your cannabis.
Saliva tests are the most common form of roadside testing. This is done by inserting an absorbance pad into the mouth, which wicks up the saliva. The pad with the saliva is then placedin a testing solution, which will show a chemical reaction if THC is present. These tests are fairly accurate but can provide both false negative and positive readings. They do not show the level of THC present, only that it is there.
In urine tests, cannabis is typically detectable for between three days after a single dose, up to 30 days for patients who take it daily.
These tests actually measure a secondary metabolite THC-COOH (11-Nor-9-carboxy-THC), which lingers as cannabinoids are stored in the body’s fat cells and are released slowly as that fat breaks down. In rare cases, and under sensitive lab settings, THC-COOH detection in urine samples has been documented in considerably longer periods, but this is seen as the exception rather than the norm. Most Urine test have a THC-COOH of 50 nanograms per millilitre (ng/mL).
THC remains detectable in blood tests for a shorter period than other testing protocols, usually around 24 hours. That can rise to 3 days for patients who take their medication daily.
Blood tests offer the most accurate results in terms of the level of active THC in your system. Rather than measuring the metabolites, blood tests detect the actual THC, which is why they show a clearer picture of recent cannabis consumption than urine or hair tests. That said, the level of THC in your blood is not an accurate reflection of impairment, more so in patients who medicate regularly and retain a baseline level of THC in their system between doses.
Hair testing has the longest detection window, and can show evidence of cannabis being taken for up to 90 days. It works through analysing a section of hair, usually the 1.5 inches closest to the scalp.
For most people, hair grows at a rate of around 1 cm (about half an inch) per month. While traces of THC technically remain in the entire hair strand, testing almost always focuses on the most recent growth, which is why the detection window is capped at around the 90 day mark.
Hair testing has been found to be less reliable for people who only take cannabis occasionally. Research suggests it is a good test for heavy, daily use cases, but it cannot reliably detect THC in people who only take cannabis infrequently and does not indicate how much was taken.
Cannabinoids get into the bloodstream through inhalation or oral ingestion. When cannabis or THC is taken orally, it is processed by the digestive acids and passes through the liver before entering the bloodstream. The onset of effects takes around 45 minutes to an hour. Taking it with food can improve bioavailability, and higher fat foods further increase bioavailability. Inhaled cannabinoids can enter the bloodstream in a matter of seconds, allowing the effects to be felt almost instantly.
There are a range of factors that will impact how long cannabis stays in your body, including your percentage of body fat, your body type, how you took your cannabis, and how strong the dose and cannabis product were.
Body fat - because cannabinoids are fat-soluble, they bind easily to the fats in your body. The more fat stores you have, the greater chance your body has of holding onto cannabinoids for longer.
Frequency and quantity - taking cannabis frequently will create an overlap of the THC metabolites stored in your system, as there will be less time for them to clear.
Potency - the more THC you take, the longer it takes for it to leave the body due to larger amounts being stored in the fat.
Method of administration - oral administration of cannabis causes THC to pass through the digestive tract and into the liver, where it is metabolised and more easily stored in body fat than if THC is inhaled, where it goes directly into the bloodstream.
THC and the metabolites produced as your body processes them can stay present in your system for a sustained period of time, as the cannabinoids are fat-soluble. This means they are stored in your fatty tissues rather than being flushed out easily and quickly.
80 minutes to 2 hours after taking THC, the metabolite THC-COOH levels in the blood reach maximum levels before they slowly start to taper off. Active THC clears the system quite quickly, passing out through urine and faeces, while THC-COOH starts to be released from your fat stores over the next few days. This slow release from fat is precisely why cannabis can be detected long after the effects wear off.
THC’s half-life is calculated at around 20-30 hours. 11-hydroxy-THC has a similar half-life of around 12-36 hours, with it being longer for patients who take high doses regularly. Half-life is the time it takes for half of the drug to leave the system. Typically, the body will eliminate a drug within four to five half-lives.
The more CBD you take in a single dose, the longer it stays in your system. A study in the journal Therapeutic Drug Monitoring found that taking 1.35 milligrams of CBD was detectable in the blood for around six hours after being taken, but higher doses were detected for longer.
To learn more, head to our full guide on how long CBD stays in your system
The half-life of CBD, or cannabidiol, varies depending on several factors, including the method of ingestion and your metabolism. Generally, the half-life of CBD is estimated to range from about 1 hour after inhalation to as long as 2 to 5 days.
Taking CBD Orally: When CBD is consumed orally on an empty stomach, it tends to have a shorter half-life. This is because it gets processed by the digestive system and metabolised by the liver relatively quickly.
Influence of Food: Consuming CBD with food, especially fatty foods, can extend its half-life. Fats enhance the bioavailability of CBD, which means that more of it is absorbed into the bloodstream. As a result, it takes longer for the body to process and eliminate CBD, thereby increasing its half-life.
Medical cannabis influences our body by interacting with the endocannabinoid system (ECS), a complex cell-signalling system that plays a key role in regulating a range of functions and processes, including sleep, mood, appetite, memory, and pain.
It has been shown to help with a huge range of health concerns. Medical cannabis has been a legal treatment option in the UK since 2018, and can be prescribed through a private clinic like Releaf for a wide range of chronic health conditions.
The main differences between medical cannabis and recreational cannabis are:
Regulation and quality control. In the UK, medical cannabis products are subject to strict regulatory oversight and pharmaceutical Good Manufacturing Practice (GMP) standards. All products are tested for purity and consistency, and come with COA showing cannabinoid content, along with a range of other quality checks. Recreational, street sourced weed is totally unregulated.
Clinical oversight. Medical cannabis must be prescribed by a doctor on the GMC Specialist Register, with ongoing monitoring.
Legal Status. Medical cannabis has been a legal treatment option in the UK since 2018. Recreational cannabis remains illegal to buy, possess, or supply, and is classified as a Class B drug.
There is no 'one-size-fits-all' approach to taking medical cannabis. The best administration method and dosage will depend on your individual needs and the condition being treated. Your prescribing specialist will work with our multidisciplinary team to create a personalised treatment plan that suits your specific needs.
In most cases, patients are recommended to 'start-low, go-slow' when taking medical cannabis for the first time. This means starting with a low dose and gradually increasing it until you achieve the desired therapeutic effects.
As above, there is no universal answer to this question. Your prescribing specialist may recommend taking your medication at a certain time of day based on factors such as the condition being treated and the type of medical cannabis being prescribed.
Releaf patients have access to a wide range of medical cannabis strains, oil, pastilles, THC vapes, and other medical cannabis product options to choose from. Your prescribing specialist will be able to advise on the most suitable option for your needs, but it may involve some trial and error to determine the right cultivar, dose, and method of administration for your unique health needs.
Edible CBD typically stays in your system for 2 to 5 days, though the actual time frame will vary based on how often you take CBD, the dosage, your metabolism, and body weight. Patients taking CBD in small doses daily, for example, may have CBD traces stay in the system longer than someone who takes a higher dose once a week.
That depends on the drug, how often it is taken, and a range of other factors. Most drugs stay in the system for a few days, with some (like medical cannabis) being detectable for up to several weeks if taken regularly. Hair, urine and blood tests will show results for far longer than a mouth swab or saliva test.
The duration that cannabis components like THC and CBD stay in your system can and do vary widely, influenced by many factors. The type of test used, the method of ingestion, dosage, and individual metabolism all play a role in how long THC may be detectable. Understanding these nuances is important, as THC can stay detectable long after the therapeutic benefits it offers wear off.
To find out if you may be a candidate for medical cannabis treatment in the UK, head to our fast and free medical cannabis eligibility checker. It takes just 20 seconds to complete, and is totally obligation-free.
Releaf - Let's redefine healthcare
It is important to seek medical advice before starting any new treatments. The patient advisors at Releaf are available to provide expert advice and support. Alternatively, click here to book a consultation with one of our specialist doctors.
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