Dry January – how testing would detect if you’d fallen off the wagon.

James Nutt

James Nutt

on Jan 24, 2024

It’s the time of year where many choose to take a break from alcohol, perhaps after an indulgent festive period, for charity or as a new year’s resolution. While we haven’t ever been asked to test to confirm someone has completed ‘Dry January’, we are frequently involved in testing to prove abstinence for serious matters, such as family law cases.

Using Dry January for illustrative purposes, below, we explore how our alcohol tests would spot whether you had abstained from alcohol and the results the different types of tests would show.


Types of alcohol tests

When testing for alcohol, we offer two types of tests: a hair strand test or a PEth (dry blood spot) test. Each of these tests offer a different insight into the nature of alcohol consumption – whether it be chronic/consistent (hair) or recent/immediate (PEth).

Depending on why the test has been requested, this will determine which test is the most appropriate. For example, in social work or family law cases we usually employ the hair strand test to establish a larger picture and pattern of alcohol usage. PEth is ideal for witnessing recent consumption. For example, in workplace drug testing.


Dry January and PEth (dry blood spot) testing

 PEth, a metabolite of alcohol, can be detected in a dried blood spot for a period of around a month. Scientific research states that PEth has a half-life of 5-6 days. This means that the value will halve every 5-6 days, reducing the prevalence of alcohol weekly. In normal circumstances, one would theoretically receive a negative test result after a month, so by the end of Dry January.

However, a small proportion of people are slow metabolisers. If this is the case, there is a possibility that the period covered by the test can be slightly longer than this.

Therefore, if a PEth sample was collected around 06 February, even if the donor had a merry Christmas and a few tipples at new year, we would not expect PEth to be detected above our reporting cut-off level. This would indicate abstinence or irregular low alcohol consumption in the approximate month prior to the sample collection.

We would still expect a level of PEth to be detected, albeit less than the cut-off proposed by PEth-net of 20ng/mL.


Dry January and hair strand testing

Testing for alcohol using a hair strand test gives a much larger window of detection. When we take a sample, we can expect to gather an idea of a person’s alcohol consumption for up to six months.

When someone ingests alcohol, the metabolites that are produced as a result enter the hair as it grows. Hair usually grows at a rate of one centimetre a month, which allows us to section the hair, by month, to establish consumption.



That said, hair strand testing would not be a suitable tool to determine abstinence within a single month sandwiched between months where alcohol was consumed. This is due to a proportion of the sample comprising of hair in the “resting phase” -when the hair is not actively growing but still contain metabolites from previous alcohol use.

When people stop consuming alcohol, levels of alcohol markers quickly drop but these levels can remain detectable for some months because of the proportion of hair in this resting phase. It can therefore take some months for all traces of alcohol markers to be eliminated from the hair following abstinence from alcohol.


Court Orders

If, for example, someone has been ordered by court to prove six months of abstinence, this is something that we can accurately report on as we will be able to see the reduction and ultimate elimination of metabolites in the hair sample. One month would be too short a timescale to effectively see this.

It is worth noting that the SOHT states that “a negative result of EtG in pubic hair is the most sensitive test for abstinence because a single alcohol consumption may give a positive result”.


In conclusion

Whether proving abstinence for legal purposes, work-placed testing or personal commitments, the choice of testing method depends on the specific context and duration in question.

Dry January aside, our tests serve as valuable tools in objectively assessing and confirming an individual's adherence to abstinence, providing clarity and accountability in important situations where the results can prove life-changing.


CTA graphic - Dual PETh Blood and ETG Testing x 2



James Nutt

James Nutt

James Nutt is Cansford’s Senior Reporting Scientist and Laboratory Manager. He has extensive knowledge and experience of toxicology in relation to family court, reporting and drug and alcohol testing.

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