How long marijuana takes depends on what you’re really asking: how long until you feel it, how long the high lasts, or how long it stays detectable in your body. The answers range from minutes to months, depending on the method of use and how often you consume it.
How Quickly You Feel the Effects
Smoking or vaping cannabis produces effects almost immediately, with the high peaking around 10 minutes after inhalation. That rapid onset is why inhalation remains the most common method of use: you can gauge how high you’re getting in real time and stop when you want.
Edibles are a completely different experience. Effects don’t appear until 30 to 60 minutes after eating, and they often don’t peak until 1.5 to 3 hours later. This delay catches a lot of people off guard. Someone eats a gummy, feels nothing after 45 minutes, takes another, and then both doses hit at once. The slow onset is caused by THC passing through your digestive system and liver before reaching your bloodstream, a much longer route than lungs to brain.
How Long the High Lasts
A high from smoking or vaping typically lasts 1 to 3 hours, though residual effects like mild grogginess can linger for up to 8 hours. Most people feel functionally normal within 3 to 4 hours of a moderate inhaled dose.
Edibles last dramatically longer. The effects can persist for up to 24 hours from a single dose, with the most intense period centered around the 2-hour mark. Even after the peak fades, many people report feeling “off” or sluggish well into the next day, especially with higher doses. This extended duration is one reason edibles are more likely to produce uncomfortable experiences for new or infrequent users.
How Long THC Stays in Your Urine
Urine testing is the most common form of drug screening, and it’s where the detection window varies the most. A single, isolated use can show up for roughly 1 to 3 days. Regular use pushes that window out significantly, and daily, long-term users can test positive for up to 5 weeks after their last use.
The standard workplace urine test, including the one required by the U.S. Department of Transportation, uses an initial screening cutoff of 50 nanograms per milliliter. If that test comes back positive, a confirmation test at 15 ng/mL follows. You need to be below those thresholds to pass.
The reason the detection window spans such a wide range comes down to how your body processes THC. Unlike alcohol, which is water-soluble and clears quickly, THC and its byproducts are fat-soluble. Your body stores them in fat tissue and releases them slowly over time. Research from Johns Hopkins found that the primary urinary byproduct of THC has a half-life of roughly 28 to 35 hours in a one-week observation window, and potentially 44 to 60 hours when tracked over two weeks. That means it takes days just to eliminate half of what your body stored from a single session.
Blood, Saliva, and Hair Tests
Blood and saliva tests detect THC over a much shorter window than urine tests, which makes them more useful for identifying recent use. After smoking, THC levels in saliva drop below 1 nanogram per milliliter within about 6 hours. Blood tests generally detect use within a similar timeframe for single sessions, though distinguishing between use 12 hours ago and use a few weeks ago remains a challenge with some testing methods.
Hair follicle tests work on an entirely different timescale. They can detect cannabis use for up to 3 months, because drug byproducts get incorporated into the hair shaft as it grows. These tests are less common for routine screening but are sometimes used in legal or custody situations. They aren’t perfect: contamination, certain foods, and even some prescription medications can produce false positives, and laboratories occasionally return inconclusive results.
What Makes THC Clear Faster or Slower
Several factors determine where you fall in those detection ranges.
- Frequency of use: This is the single biggest factor. Someone who smoked once at a party faces a fundamentally different detection window than a daily user. Chronic use leads to a large reservoir of THC stored in fat cells, which trickles out slowly over weeks.
- Body fat percentage: Because THC lodges in fat tissue, people with higher body fat tend to retain it longer. Two people can use the same amount on the same day and test differently a week later based on body composition alone.
- Metabolism: A faster metabolic rate clears THC more quickly. Age, activity level, and genetics all play a role here.
- Stress and fasting: This one surprises people. Research from the EPA has shown that conditions triggering fat breakdown, including food deprivation and stress hormones, can release stored THC back into the bloodstream. In animal studies, fasting and stress both measurably increased blood THC levels in subjects that had been previously exposed. This means crash dieting before a drug test could theoretically work against you.
Can Secondhand Smoke Cause a Positive Test?
It’s possible, but only under extreme conditions. A Johns Hopkins study placed nonsmokers in a sealed, unventilated room with smokers who went through 10 high-potency cannabis cigarettes over the course of an hour. Under those conditions, some nonsmokers produced enough THC in their urine to trigger a positive result on a standard workplace drug test. They also reported feeling mildly intoxicated and showed slight cognitive impairment.
When the same experiment was repeated with ventilation fans running, nonsmokers showed no drug effects at all besides increased hunger. The researchers described the unventilated scenario as a “worst case” that couldn’t realistically happen to someone without their knowledge. In practical terms, brief exposure at an outdoor concert or walking past someone smoking is extremely unlikely to cause a positive test.
Rough Timeline by Test Type
- Saliva: Up to about 6 to 12 hours for a single use
- Blood: Generally hours to a few days, depending on use frequency
- Urine: 1 to 3 days for a single use, up to 5 weeks for heavy daily use
- Hair: Up to 3 months
If you’re facing a specific test with a specific timeline, the most reliable variables in your control are how much and how often you’ve used. No detox drink or supplement has strong evidence behind it for speeding up THC clearance. Time and abstinence remain the only proven approaches.