Most hair follicle tests can detect cannabis metabolites for up to about 90 days after last use, and a heavy daily user may test positive somewhat longer. Hair grows roughly half an inch per month, so a 1.5-inch sample taken near the scalp covers around three months of history. How long cannabis actually stays in your hair depends on how much you use, how often, and how your body clears THC.
Key Features That Change How Long Cannabis Stays in Hair
- Frequency of use: occasional use typically clears sooner than daily, high-potency use.
- Dose and potency: concentrates and high-THC edibles leave more metabolite behind.
- Hair length: a sample cut close to the scalp reflects roughly the last 90 days.
- Body chemistry: metabolism, body fat, and hydration affect how fast THC-COOH clears.
- Hair treatment: bleaching, relaxing, and repeated dyeing can lower detectable residue.
- Lab cutoffs: testing labs use different sensitivity thresholds, so results vary by provider.
- Secondhand exposure: incidental smoke rarely registers, but chronic exposure can.
How Hair Testing Works: Materials and Specs
Hair tests do not look for THC itself. They look for THC-COOH and related metabolites that become trapped inside the keratin shaft as the strand grows. A standard collection is a pencil-thickness lock of roughly 100 to 120 strands cut close to the scalp, sometimes sectioned to show a timeline. The lab washes the sample to remove surface contamination, screens it, then confirms any positive with GC-MS or LC-MS/MS. Because the residue sits inside the strand rather than on it, shampoo, clarifying washes, and masks do not reliably change a result.
can cannabis be detected in hair after one use
Shipping and Returns
Orders from our shop ship in plain, discreet packaging with tracking, and every batch is third-party lab tested with results available on request. If something arrives damaged or isn't right for you, contact us for a return or replacement under our standard policy.
Does cannabis grow out of your hair over time?
Yes. Once metabolites are sealed inside the strand, only new growth moves them away from the scalp, so hair that has grown past the detection window generally tests negative when sampled near the root.
How Far Back Can a Hair Drug Test Detect Cannabis?
Can a single use show up on a hair test?
It can, but usually at a much lower concentration. One-time use is far more likely to fall below a lab's cutoff than months of daily use.
Is a hair test better than a urine test?
Not better, just different. Urine detects recent use over a few days, while hair covers a much longer window and is harder to tamper with.