Legal FAQ’s

FAQ’s – Hair Testing for Alcohol & Drugs (Legal Services)

Why is Hair Testing for Drugs so useful?

Drugs are incorporated into growing hair. Because scalp hair grows at an average rate of 1 cm per month, the analysis of a hair sample will provide retrospective evidence for drug use. Therefore analysis of 3 cm of scalp hair should detect drug abuse during the previous 3 months approximately (it takes a few weeks for drugs to get into the hair).

Is the analysis sensitive?

Yes. Modern technology has advanced so much in the previous few years, it is possible to detect occasional drug use.

Is hair testing regulated?

Hair testing is not regulated by government. Testing organisations however adhere to the practices recommended by the Society for Hair Testing (

What information do they put on the forms that go with my sample?

For laboratory testing, a special chain-of-custody form is required. Information on declared medication (prescribed and over-the-counter) should also be provided at the time of collection.

What kinds of tests would I have to take? What drugs would be tested for?

In the absence of a specific drug request, hair samples are screened for a ‘standard panel’ which includes a range of commonly abused drugs.

How reliable is hair testing?

When both screening and confirmatory tests are conducted, the combined tests themselves become virtually 100% dependable. This is due mainly to modern analytical instrumentation used in the analysis.

Where would I be tested?

Hair samples are collected by trained nurses at a central Belfast location. NIVHA also carries out hair testing work for a number of occupational physicians across the province.

What actually happens when I go to be tested?

A sample of hair (preferably 2 samples of scalp hair) about the width of a thin pencil is collected from the back of the head.

Non-scalp hair can also be used (body, axilla, pubic) in the absence of scalp hair. Pubic hair is not suitable for alcohol metabolite analysis.

Testing is a two-stage process. First, an initial (screening) test is administered. If it is positive for one or more drugs, then a second, confirmatory test is usually conducted for each identified drug. The confirmation test uses a different, more sophisticated chemical process. A person, who is trained in the collection process, seals and labels the specimen, then prepares both the specimen and its accompanying paperwork for shipment to the laboratory. Each step of the process is documented on a “chain of custody” form. The collection and chain of custody procedures ensure the specimen is properly identified and tracked throughout the testing process.

How long after use can drugs be detected in hair?

Drug abuse can be detected many months after the last instance of use (3 cm/3 months is standard analysis practice. The detection window is longer with non-scalp hair.

Can I test positive for environmental exposure?

Yes. In the absence of drug metabolites there will be some possibility that the drug presence in hair was due to environmental exposure. This is of course less likely with non-powdered drugs (tablets). The presence of metabolite(s) precludes this possibility.

What will be done to me if I test positive?

The presence of the drug will be reported to the organisation requesting the test – usually solicitor.

What are the alternatives to hair testing?

Hair testing is the best way to demonstrate retrospective drug abstention. Urine analysis can also be used but the detection window is much shorter. The use of both hair and urine is often used – the urine picks up more recent abuse and can detect drug metabolites.

How can alcohol be detected in hair?

Alcohol itself cannot be detected in hair, due to its volatility. However there are a number of minor alcohol metabolites, which do become incorporated into hair. The measurement of these metabolites can be used to provide evidence of excessive alcohol consumption.

What are these metabolites?

There are 2 types:

  • Ethyl glucuronide (EtG)
  • Fatty acid ethyl esters (FAEE’s)

How reliable is this testing for alcohol?

If the concentration of EtG in scalp hair lies above a defined cutoff value, then this represents fairly strong evidence for excessive alcohol consumption. It cannot be used to determine abstinence.

The presence of FAEE’s above the cutoff provides additional evidence and increases to level of confidence in the assessment.

Of course this analysis is not totally definitive and each case should be judged on its own merit. Other evidential information should also be considered.

Can hair alcohol analysis be carried out with drug analysis ?

Yes. The sample selected for EtG analysis can also be used for drug analysis. The second hair sample collected can be reserved for FAEE analysis in the event of the EtG result being high.

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