What length of time can hair drug test results cover?

In addition to their accuracy, hair drug tests are often chosen because they’re able to determine long-term patterns of drug abuse.  

Has substance misuse risen in young people since Covid?

How far back does a hair drug test go?

Hair drug test collection

The simple answer is that it depends on the length of the hair being tested. It takes about 5–6 days for the hair growing from the root to appear above the skin and therefore be available for detection.

Our hair grows at an average rate of 1 cm per month, but between different individuals, it can vary from 0.7 cm to 1.5 cm per month. This means that a 6cm long section of head hair can approximately provide a 6-month drug use profile.

Hair sample drug tests explained:

Hair drug tests work by detecting the traces of the parent drug, metabolites, and constituents (chemical signatures), which have entered the bloodstream and been deposited into the hair shaft. These chemical signatures are identified by their unique molecular structures and are therefore highly specific.

The drug laboratory results are assessed by a legal medical expert who can provide an in-depth report. A drug test report describes the levels and implications of the drugs detected. They will offer a clinical insight into the pattern of substance misuse revealed. The expert can identify potential signs, symptoms, and risks that you might see by looking at the drug test results.

If required, our expert is able to answer further questions on the clinical aspects arising from the identified substance misuse and recommend further testing that may be useful to the court when assessing sustained misuse.

Our expert is also available if required to complete a full psychiatric report, identifying whether a misuser is suffering from a clinical syndrome such as drug dependency or harmful misuse and identifying potential treatments.

How to stop prescription drugs from escaping lab detection

Segmented Hair Drug Testing

Segmented hair drug test results

We can segment hair samples into monthly 1 cm sections, so a month-by-month profile of drug use can be attained to provide a detailed historical profile of an individual’s drug exposure.

If a hair drug test is to cover 3 months, a month-by-month analysis will provide 3 individual results for each of the months. So segmented analysis is useful if you want to see a trend in drug use, such as a decrease or increase in drug use over time, or to highlight irregular use.

This is of particular use when monitoring the compliance and effectiveness of opiate substitute medications such as methadone for heroin addiction. An individual who is ‘doing well’ should have sequential hair drug results showing a reduction of the heroin chemical signatures over time, whilst the methadone levels increase with dose titration to a stable level.

Why use hair segmentation drug testing?
So how long does a hair drug test go back?

Although a Hair Drug Test can technically detect drugs for years, we usually recommend a maximum of 6 months for highly accurate results. This is due to hair deterioration.

However, if you’re looking to show a 12-month insight then it’s possible for hair drug tests to go back this length of time.

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