Hair Strand Test Results Explained: How to Read a Hair Drug Test Report, Line by Line

Updated 19 Oct 2026 · By the DrugTestAnswers Editorial Team

A hair strand drug test report looks more complicated than it is. Each drug class gets a result, usually "negative" or "positive", and a positive normally comes with a measured amount in picograms per milligram of hair (pg/mg) next to the lab's cutoff. Negative means the lab found less than its cutoff, not that it found nothing. Positive means a confirmation test measured the drug or its breakdown product above that cutoff. Below we go through a report section by section, explain what the numbers can and can't tell you, and cover what to do if a result looks wrong. We may earn a commission if you buy through our links.

The short version

• Negative: below the cutoff on the screen, or screened positive but didn't confirm. It doesn't mean zero.
• Positive: a mass spectrometry confirmation found the drug above the confirmation cutoff. Employer tests then go to a doctor for review before anyone sees a final answer.
• The number (pg/mg): how much of the drug was in each milligram of hair. Higher usually points to heavier or more frequent use, but it can't give a dose or an exact date.
• The window: roughly the last 90 days for a standard head-hair sample cut close to the scalp. The most recent week or so usually isn't in the sample yet.

The parts of a hair test report

Layouts differ between labs, but almost every report carries the same blocks of information. Here's what each one is for.

Negative: what it really means

A negative result says the sample didn't reach the cutoff, nothing more. Hair holds drugs in very small amounts, and a lab only reports a positive above a set threshold, partly so tiny traces from environmental exposure don't get reported as use. That's why one-time or light use, especially of marijuana, can come back negative even though it happened within the window.

A sample can also be negative because it screened positive and then failed to confirm. The first test is a quick antibody screen, called an immunoassay, that flags samples worth a closer look. The second is the precise test. If the precise test doesn't find the drug above its cutoff, the overall result is negative and most reports won't mention the screen at all.

Positive: how a lab gets there

Every positive on a lab-based hair test goes through two stages:

1. Washing. Before testing, the lab washes the hair to remove sweat, smoke residue and anything sitting on the surface. Some labs test the wash liquid too and compare it with what's inside the hair.
2. Screening. The hair is cut or ground and dissolved, and the liquid goes through an immunoassay screen for each drug class.
3. Confirmation. Anything that screens above the cutoff is tested again by gas or liquid chromatography with mass spectrometry (GC-MS/MS or LC-MS/MS), which identifies the exact compound and measures it.

For cocaine, many labs also require a breakdown product such as benzoylecgonine, norcocaine or cocaethylene to be present, which helps separate use from cocaine dust that landed on the hair. For marijuana, labs look for THC-COOH (sometimes written THCA), a compound the body makes after THC is used, rather than THC itself, because THC can come from smoke in the air. Our page on how the hair drug test method works goes through each lab step in more depth.

Understanding pg/mg and cutoff levels

Hair results use picograms per milligram. A picogram is a trillionth of a gram, so a result of 500 pg/mg means half a billionth of a gram of drug in every milligram of hair. Urine tests use nanograms per milliliter, which is a different scale entirely, so hair and urine numbers can't be compared directly.

Each lab sets its own cutoffs, and the report should list them. For a sense of the usual range, here are the cutoffs HHS proposed in 2020 for federal hair testing. Those guidelines still haven't been finalized, but they built on a 2004 proposal and are close to what many private labs use.

Source: HHS/SAMHSA proposed Mandatory Guidelines for Federal Workplace Drug Testing Programs using hair, Federal Register, September 2020. Expanded panels add drug classes such as benzodiazepines, barbiturates, methadone or fentanyl, with each lab's own cutoffs. For urine and oral fluid numbers, see our drug test cutoff levels table.

Notice how low the marijuana confirmation cutoff is compared with the others. THC-COOH gets into hair in tiny amounts, so labs have to look for very small traces. Even so, hair tests are generally less sensitive to occasional marijuana use than to regular use, which is why results for light smokers vary so much.

Is there a "levels chart" that tells you how much someone used?

People often search for a chart that turns a pg/mg number into "light", "moderate" or "heavy" use. Some labs and researchers have published rough bands, mostly for cocaine, and a few reports include a comment along those lines. Treat them with real caution:

• Hair color changes the number. Melanin, the pigment in darker hair, binds some drugs (cocaine, amphetamines and opioids especially) more strongly than lighter hair does. Two people with the same use can get quite different numbers.
• Treatments lower the number. Bleach, permanent dye, relaxers and perms can reduce drug levels in the hair, which can make heavy use look lighter.
• Growth rate varies. Head hair grows about half an inch (around 1 centimeter) a month on average, but that differs from person to person and between head and body hair.
• Dose and purity are unknown. Street drugs vary widely in strength, so the same number of uses doesn't produce the same amount in hair.

The honest reading is: a result near the cutoff fits with lighter or less frequent use, and a result many times the cutoff fits with heavier or more frequent use. Beyond that, no chart can reliably tell how many times, how much, or on which days.

Alcohol results use a separate scale

Some panels test for ethyl glucuronide (EtG), a marker of drinking. The Society of Hair Testing's consensus uses about 5 pg/mg as the level that suggests repeated drinking and about 30 pg/mg as the level that strongly suggests chronic heavy drinking. These are interpretation guides, not exact measures of how much someone drinks.

Segment results: when a report splits the hair into months

Most workplace tests treat the hair as one sample covering about 90 days. Some tests, more common outside employment, cut the strand into sections, often 1 to 1.5 centimeters each, and test each one separately. The report then shows a row for each segment, for example "0 to 1 cm", "1 to 2 cm" and "2 to 3 cm", with the segment nearest the scalp being the most recent.

Segment results can show a trend, such as levels dropping over three months, which can be consistent with someone cutting down. The timing is approximate. Hair grows at different rates, drugs can move a little along the strand, and newly grown hair takes about a week to rise above the scalp, so each segment should be read as "roughly this month", never as an exact date range.

Head hair versus body hair results

If there wasn't enough head hair, the collector may have taken hair from the arms, legs, chest or armpits. Body hair grows more slowly and has longer resting phases, so a body hair result can reflect use going back further than 90 days, sometimes up to a year, and the window can't be pinned down as precisely. The report should say which type was tested. See what body hair can be used for drug testing for how collectors decide.

Other results you might see

You won't see "dilute" on a hair report. That's a urine term.

How long results take, and who sees them first

Negatives are usually reported within a few business days of the lab receiving the sample. Positives take longer because of the confirmation step and, for employer tests, the medical review. If you took the test for a job, the result normally goes to the employer or the company running the program, not to you, unless you ask for a copy. For a home kit, the lab sends the report straight to you, usually online.

A worked example

Here's a made-up 5-panel report to show how the pieces fit together. Say the lines read: marijuana negative, cocaine positive, opiates negative, amphetamines negative, PCP negative. Beside cocaine, the confirmation column shows cocaine at 1,450 pg/mg and benzoylecgonine at 210 pg/mg, with cutoffs of 500 and 50.

• Which line matters: only cocaine. Every other class was below its cutoff.
• Was it real use or surface contamination? The lab found the breakdown product as well as cocaine itself, after washing the sample. That's the pattern labs treat as use rather than outside exposure.
• How heavy? Roughly three times the cocaine cutoff. That fits with more than a one-off, but it can't say how many times or how much, especially without knowing hair color and treatment history.
• When? Sometime in roughly the three months before the collection date, minus the most recent week or so.
• What happens next? For a job test, the medical review officer calls before the employer gets anything. Cocaine has very few prescription explanations, so a verified positive is likely unless there's a lab or paperwork problem.

Now picture the same report with cocaine at 520 pg/mg and benzoylecgonine at 55. It's still positive, because both are over their cutoffs, but only just. A result that close to the line is where questions about exposure, retesting and lab procedure carry the most weight.

The medical review step

For most employer programs, a lab positive doesn't go straight to the employer. A medical review officer, a licensed doctor, first contacts you to ask whether there's a legitimate explanation, such as a prescription for oxycodone, Adderall or a benzodiazepine. If you have a valid prescription that accounts for the result, the doctor can report it as negative. Have the pharmacy name, prescribing doctor and dates ready, and answer the call, because if the doctor can't reach you, the positive may be reported anyway. Our guide to screen versus confirmation results explains the same two-step logic for urine tests.

What results can't tell you

• The last week or so. Hair that formed during the most recent days is usually still below the scalp when it's cut.
• Exact dates. Even segment testing only gives approximate months.
• Impairment. Hair shows past use over weeks or months, not whether someone was under the influence on a particular day.
• How it was taken. Smoking, swallowing and snorting all end up in hair the same way.
• Single use, reliably. One-time use may or may not cross the cutoff, depending on the drug, the dose and the person.

If a result looks wrong

1. Check the basics. Confirm the specimen number, your details and the collection date match your copy of the form.
2. Look at what was actually found. A specific compound (say, oxycodone rather than "opiates") helps you match it to a prescription.
3. Talk to the medical review officer about any prescription, recent surgery or other medical treatment.
4. Ask about a retest. Many labs keep part of the sample. Ask whether it can be retested, ideally at a different accredited lab, and what it costs.
5. Raise exposure questions in writing. If you were around heavy smoke or handled drugs at work, say so. Washing procedures and metabolite requirements are meant to address this, but it's worth recording. Our page on secondhand smoke and hair tests and our article on cocaine false positives in hair go into the evidence.

Reading a home hair test result

Lab-based home kits send a report built the same way: a line per drug class, negative or positive, and often the cutoff used. There's no medical review officer or chain-of-custody form, so the report is for your information only and an employer won't accept it. That makes a home kit useful for one thing: seeing where you stand before an official test. If you have a test coming up, a home hair test is the sensible first step. Our comparison of the best hair follicle drug test kits covers panels and turnaround times.

Product facts: Old Style Aloe Toxin Rid

Once people understand their result, many ask about the cleansing shampoos sold for hair tests. The most discussed is Old Style Aloe Toxin Rid from TestClear. Here's what is and isn't known:

• What TestClear says: it's a deep-cleansing shampoo meant to strip residue and buildup from the hair and scalp.
• Maker's directions, briefly: wash with a regular shampoo first, then apply Aloe Toxin Rid to damp hair and scalp, leave it on for 10 to 15 minutes, rinse, and repeat over several days before the test.
• What isn't proven: there's no independent, published research showing it lowers drug levels enough to change a hair test result. Nothing on this page should be read as a promise of a negative. The only sure way to pass is not to use.

If you want to look at it anyway, you can see Old Style Aloe Toxin Rid and its current price at TestClear. For the full directions and the evidence gaps, read our Aloe Toxin Rid review and how-to guide.

A word on Macujo and Jerry G

The Macujo and Jerry G methods are home routines that layer vinegar, salicylic acid products, laundry detergent and (in Jerry G's case) bleach and dye on the hair over several sessions. They're popular online, but there's no independent evidence they reliably change a hair test result, and they can burn the scalp and badly damage hair. Labs may also note heavily damaged samples. Never mix bleach with vinegar, acids, ammonia or household cleaners: the combination can release toxic gases. If you've already treated your hair, tell the collector; don't hide it.

Where these numbers come from

Cutoff figures are from the HHS/SAMHSA 2020 proposed hair guidelines in the Federal Register and the 2004 proposal they were based on. Alcohol marker levels follow the Society of Hair Testing consensus. Growth rates, melanin binding and treatment effects come from published forensic toxicology research. Product directions are summarized from TestClear's product page. See our editorial methodology for how we check sources.

Tests this page doesn't cover

This guide is about workplace and personal hair testing. It doesn't apply to DOT-regulated testing (trucking, transit, rail, pipeline, maritime), FAA aviation testing, federal employee programs, military testing, or court, probation and parole testing. Don't use any product mentioned here to try to affect those tests. Tampering can count as a refusal and may be illegal.

Disclaimer and help

Informational only, not medical, legal or financial advice. Tampering with a drug test may be illegal and can count as a refusal or a failed test. The only sure way to pass is not to use. For free, confidential support around the clock, call the SAMHSA National Helpline at 1-800-662-4357. If you're in crisis, call or text 988.