If you’ve enjoyed cannabis, you might have a lingering question long after the effects have worn off: how long does it stay in your hair? Unlike other methods of detection, a hair follicle test has a much longer memory. It’s a common concern for job screenings or personal curiosity, and the answer isn’t as simple as a few days.
Hair tests are designed to detect substance use over an extended period. When you consume cannabis, its compounds, known as metabolites, enter your bloodstream and are eventually deposited into your hair follicles. As your hair grows, these markers become a permanent part of the hair strand, creating a timeline of your consumption.
The 90-Day Window for Hair Follicle Tests
The most frequently cited timeframe for cannabis detection in hair is up to 90 days. This is because standard hair tests typically analyze the 1.5 inches of hair closest to your scalp, which represents about three months of growth. If you’ve consumed cannabis within that period, it’s likely to show up. However, this isn’t a perfect clock. Factors like your hair growth rate, metabolism, and the frequency of your use all play a significant role.
Factors That Influence Detection Times
Not everyone will test positive for the full 90 days. Several key factors can shorten or lengthen the detection window. Frequency of use is the biggest one; a single, one-time use may only be detectable for a few days in the hair follicle before the hair strand grows out, while chronic, heavy use leads to a much higher buildup of metabolites. Your hair color and type can also matter, as some studies suggest darker, coarser hair may retain more drug metabolites than lighter, finer hair.
Can You Remove THC from Your Hair?
Many people search for quick fixes or detox shampoos to beat a test. While these products claim to strip toxins from your hair, their effectiveness is highly debated and often unreliable. They may cause damage or only work superficially. Because the metabolites are embedded inside the hair shaft, simply washing your hair is not enough to remove them. The most reliable way to pass a hair test is through a period of abstinence.
Hair Tests vs. Other Detection Methods
It’s helpful to understand how hair testing compares to other methods. Urine tests, for example, are far more common and detect recent use—typically from a few days to several weeks, depending on frequency. Blood tests have an even shorter window, usually just hours to a couple of days. Hair testing is unique because it provides a long-term history, making it one of the most challenging tests to pass if you’ve been a regular user.
In summary, while the 90-day rule is a good general guideline for how long weed can be detected in your hair, your individual results will vary. The most important factors are how often you consume it and your body’s unique biology. If you have an upcoming screening, the safest approach is to be informed and plan accordingly.