How Long Does THC Stay in Your System?

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How Long Does THC Take to Leave Your System?

Whether you’re preparing for a drug test or just curious about how cannabis affects your body, it’s natural to ask: how long does THC take to leave your system? The answer isn’t simple. It depends on a variety of factors including how often you use it, how much you use, and how your body processes it.

THC (tetrahydrocannabinol) is the psychoactive compound in cannabis that makes you feel high. Once you use cannabis—whether by smoking, vaping, or consuming an edible—THC enters your bloodstream and is distributed throughout the body. From there, it’s broken down into metabolites, mainly THC-COOH, which are then stored in fat and gradually excreted.

Here’s what you need to know about how long THC sticks around in your system—and why it varies from person to person.

Average Detection Times by Test Type

THC can be detected in your body using several methods. Each one has a different detection window.

Blood

  • Occasional use: 1–2 days

  • Frequent use: Up to 7 days

  • Chronic daily use: Sometimes longer
    THC leaves the bloodstream quickly, but in regular users, it can linger in trace amounts.

Urine

  • Single use: Up to 3 days

  • Moderate use (2–4 times a week): 5–7 days

  • Daily use: 10–30 days

  • Heavy long-term use: 30–60+ days
    Urine tests look for metabolites (not THC itself), which can hang around for weeks, especially in regular users.

Saliva

  • Occasional use: 24–72 hours

  • Regular use: Up to a week
    Saliva tests are often used for roadside drug testing and are aimed at catching recent use.

Hair

  • Up to 90 days
    Hair follicle tests are designed to detect long-term patterns of use. As your hair grows, THC metabolites are trapped in the strands. These tests won’t detect recent use (within the past few days), but they’re difficult to “beat” if you’ve used cannabis regularly over the last few months.

What Affects How Long THC Stays in Your Body?

Frequency of Use

This is the single most important factor. If you smoke once a month, THC will likely clear your system in a few days. If you use it daily, it can take weeks to fully leave your body. The more you use, the more is stored in your fat cells, which slowly release it over time.

Body Fat and Metabolism

THC is fat-soluble, meaning it binds to fat in your body. People with a higher body fat percentage may retain THC metabolites longer. Likewise, a slower metabolism can mean longer detection times. Hydration, diet, and exercise all play a role too.

Method of Consumption

Smoking or vaping causes THC to hit your bloodstream almost instantly and may leave faster than THC ingested through edibles. Edibles take longer to process and can result in extended release of THC, meaning they may stay in your system longer.

Dose and Potency

Higher THC content means more of it for your body to break down and store. A single puff of low-THC cannabis will clear faster than a strong edible or a few high-potency joints.

How Long Does the High Last?

Although THC can stay in your system for weeks, the psychoactive effects usually wear off much sooner.

  • Smoking/vaping: 1 to 3 hours

  • Edibles: 4 to 8 hours (but some residual effects may linger for 24+ hours)

  • Tinctures or oils: Varies depending on strength and dose

Even if you no longer feel high, your body may still be breaking down and eliminating THC metabolites.

Can You Speed Up the Process?

There’s no guaranteed way to flush THC out of your system quickly, but some people try:

  • Drinking lots of water (which may dilute urine but won’t remove THC)

  • Exercising (which might temporarily release more THC from fat into the bloodstream)

  • Eating a clean, low-fat diet

  • Taking detox drinks or supplements (these have mixed and unreliable results)

Be cautious—detox kits often promise fast results, but there’s limited scientific evidence to support them.

Drug Testing in the UK

In the UK, cannabis is a Class B drug, and drug testing is increasingly used in the workplace—especially in safety-critical jobs such as driving, construction, or transport. Employers may use urine, saliva, or hair testing to check for recent or long-term use.

Police in the UK also use roadside saliva tests to check for recent cannabis use while driving. If THC is detected above the legal threshold (2 micrograms per litre of blood), you can be prosecuted for drug driving, even if you feel sober.

Final Word

THC can stay in your system anywhere from a couple of days to over a month, depending on how much you use, how often, and how your body processes it. Occasional users usually eliminate it quickly, but for regular or heavy users, the process can take significantly longer.

If you have a drug test coming up, or if you’re re-evaluating your cannabis use, knowing how THC works in the body helps you make informed choices. Everyone processes cannabis differently, so there’s no universal timeline—just general guidance shaped by lifestyle, biology, and habit.