Hair follicle drug testing
A single hair sample can provide months of retrospective evidence of drug or alcohol use — collected under full chain of custody and analysed by accredited laboratories, so the result is properly documented for use in court.
How it works
How hair testing works
Drugs and alcohol metabolites are incorporated into hair as it grows. Scalp hair grows at an average rate of approximately 1 cm per month, so each centimetre of hair holds a record of roughly one month. Standard practice is to analyse the 3 cm closest to the scalp — approximately the previous 3 months — and longer hair can be segmented for a month-by-month picture.
It takes roughly one to two weeks for drugs to appear in growing hair, so hair testing answers questions about patterns of use over months rather than the last few days. Where recent use also matters, hair is often instructed together with a urine test — retrospective and recent evidence in one instruction.
This page is a general guide. It is not legal, medical or technical advice. Laws, guidance and laboratory methods change, so check the current requirements for your own case. Detection windows are indicative. They vary with the substance, dose, how often it is used and the individual. Last reviewed .
Follicle or strand — which is it?
The two names describe the same test. The laboratory analyses the hair shaft — the strand — not the follicle beneath the skin. "Hair follicle test" is the name most people search for; "hair strand test" is the name courts and laboratories tend to use. The sample, the analysis and the report are identical.
What a hair test can show
- Retrospective drug use — evidence of use many months after the last instance, on a standard panel of commonly abused drugs or a targeted request.
- Abstinence — hair testing is well suited to supporting a statement of abstinence over a defined period, often instructed in care proceedings and contact disputes.
- Alcohol use over time — through the alcohol metabolite EtG, with FAEE as an optional second marker. A low EtG result is consistent with abstinence or light drinking but does not rule out occasional drinking; a raised result counts against abstinence. The same sample can serve both drug and alcohol analysis.
Hair testing reflects use over the entire growth period and is unlikely to detect occasional or low-level use — an honest limitation that matters when choosing the right sample. Our sample comparison guide shows how hair compares with urine, oral fluid, blood and nail.
Collection, step by step
- Book. Solicitors and social workers can generate a quote or fee note online; employers can request a workplace quote; individuals can see private testing options.
- Attend — or we come to you. Collection at our Belfast centre, by arranged appointment in Dublin city centre, or at a solicitor's or social worker's office anywhere on the island of Ireland.
- Verified collection. The collector verifies identity, takes a pencil-width sample from the back of the head, then seals and labels it with full chain-of-custody paperwork.
- Accredited analysis and reporting. Screening and confirmatory analysis by ISO 17025 accredited laboratories, to Society of Hair Testing guidelines, with a clear report prepared for court use, delivered securely and digitally.
Who instructs hair testing
- Solicitors and social workers — care proceedings, safeguarding casework and contact disputes, where months of history decide the question.
- Employers — where retrospective abuse is to be detected, such as pre-employment screening in safety-critical roles.
- Private individuals — personal or family reasons, with the same professional standard as every NIVHA test. We do not offer home kits.
Common questions
Hair testing — your questions answered
How far back does a hair follicle drug test go?
Standard practice is to analyse the 3 cm of hair closest to the scalp, which represents approximately the previous 3 months. Longer scalp hair can be segmented to look further back, and non-scalp hair (body hair) carries a longer, less precisely defined detection window. It takes roughly one to two weeks for drugs to appear in hair, so a test does not reflect the last few days.
Is it a hair follicle test or a hair strand test?
They are the same test. The laboratory analyses the hair shaft — the strand itself — not the follicle beneath the skin. "Hair follicle test" is simply the more common name. Whichever name appears in your instruction or court order, the sample and analysis are identical.
How much hair is taken, and will it be noticeable?
A trained collector takes a sample about the width of a thin pencil — preferably two samples of scalp hair — from the back of the head, where it is least visible. If scalp hair is not available, body hair can be used instead.
What drugs are tested for?
In the absence of a specific request, hair samples are screened for a standard panel covering a range of commonly abused drugs. Specific drugs can be added or targeted where a case requires it.
How reliable is hair drug testing?
Non-negative screening results are confirmed by a more specific method at an accredited laboratory before they are reported. Accredited laboratories work in line with the consensus guidelines of the Society of Hair Testing.
Can someone test positive from environmental exposure?
It is possible for drugs to be present in hair through environmental exposure — less likely with non-powdered drugs such as tablets. This is why laboratories look for drug metabolites: their presence, and the concentrations detected, make environmental exposure much less likely as an explanation, alongside the laboratory’s washing procedures.
Does bleached or treated hair affect the result?
Bleaching, dyeing and perming can reduce both alcohol markers, and hair products containing ethanol can raise FAEE. Please tell the collector about any treatments. The laboratory takes hair condition into account, and each case is interpreted on its own merits.
Can hair be tested for alcohol as well?
Yes. Alcohol itself is too volatile to persist in hair, but its minor metabolites — ethyl glucuronide (EtG) and fatty acid ethyl esters (FAEEs) — become incorporated into growing hair. The results show the pattern of drinking over a period of months and are read alongside the case history. The same sample can be used for both drug and alcohol analysis.
More questions about attending an appointment? See what happens at a test or our full information hub.
Arrange a hair follicle test
Solicitors and social workers can generate a fee note in minutes. Employers and individuals — talk to us and we will recommend the right test, in confidence.