If you have a hair follicle drug test coming up, the short answer is that cannabis is typically detectable for up to 90 days — and heavy daily users can test positive for six months or longer. Hair testing builds a long timeline because cannabinoid metabolites settle into the growing hair shaft and stay there as it lengthens. How long cannabis stays in hair depends on how much you use, how fast your hair grows, and how long the sample is.
How Often Should You Smoke for a Hair Test to Fail?
How Long Does Cannabis Stay in Hair?
Most labs report a detection window of about 90 days for head hair, which matches roughly 1.5 inches of growth at the average rate of half an inch per month. Chronic, high-potency users can occasionally test positive beyond that window, while one-time use is less likely to register at all.
Key Features of Hair Follicle Cannabis Testing
- Typical detection window: about 90 days for head hair, longer for some heavy users.
- Timeline is growth-based: head hair grows roughly 0.5 inch (about 1.3 cm) per month.
- Primary analyte: THC-COOH, the same metabolite measured in urine tests.
- Two-step process: an immunoassay screen, then GC-MS or LC-MS/MS confirmation.
- Sample: a pencil-thick lock of hair, around 100 strands, cut close to the scalp.
- Body hair grows more slowly, so it can reflect a much longer history than head hair.
- Shampoos, bleach, and dye may lower concentrations but rarely guarantee a negative result.
What the Test Measures
Hair testing looks for deposited cannabinoid metabolites rather than plant material itself. Labs run a screening immunoassay, then confirm any non-negative result with mass spectrometry; federal hair-testing guidelines propose a screening cutoff near 1 pg/mg for THC-COOH and a confirmation cutoff near 0.1 pg/mg. Melanin binds cannabinoids, so dark, coarse hair can hold slightly more of the metabolite than fine or light hair.
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Ordering From Eden Cannabis
Orders are packed discreetly, shipped with tracking, and covered by our standard store policy. If anything arrives damaged or is not what you expected, contact our team and we will make it right.
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Can One-Time Use Show Up on a Hair Test?
Possibly, but it is less likely than with frequent use. A single exposure may fall below the lab's cutoff, and results vary with dose, potency, and individual metabolism.
Does Bleaching or Detox Shampoo Clear Cannabis From Hair?
Not reliably. Chemical treatment can lower measured concentrations, but labs expect damaged samples and outcomes are unpredictable, so these products should not be counted on.
How Long Should You Abstain to Pass a Hair Test?
Head hair holds roughly a three-month record, so about 90 days of abstinence is the usual benchmark for a clean sample. Heavy, long-term users may need longer.