What medications can cause a positive alcohol test?

Liz Wood AlphaBiolabs

By Liz Wood, Health Testing Specialist at at AlphaBiolabs
Last reviewed: 20/11/2023

What is alcohol testing?

Alcohol testing is the analysis of one or multiple samples from an individual to look for the presence of alcohol or biomarkers related to alcohol consumption or alcohol misuse.

The type of alcohol test used depends on what you are looking for – some tests are better at detecting very recent alcohol use, whilst others are good for determining if someone is a chronic alcohol user and can provide a longer overview of alcohol use. 

Alcohol testing can be laboratory-based, meaning your samples are processed at a laboratory by specially qualified and trained staff, an at-home test, or a point of care test (POCT).

Laboratory, POCT or at-home testing all have their advantages and disadvantages. 

Laboratory tests are always the most accurate. Depending on the type of sample, they can give information on how much alcohol has been consumed over a longer period of time than most POCT or at-home tests. The results should come as a report format, which details the findings of the testing and might give a quantifiable result.

Most laboratories that conduct alcohol testing will have the capacity to test multiple sample types. Because of the nature of the laboratory process, laboratory tests can’t give you instant results and are usually more expensive than POCT or at-home tests. 

POCT or at-home tests might be cheaper than a laboratory test. Some will be able to give you instant results – for example, some at-home urine tests work a bit like a pregnancy or Covid-19 test using a test cassette. 

Although POCT or at-home tests benefit from instant results, they rely on the sample provider or collector performing and reading the results of the test accurately. These tests also won’t be able to give you quantifiable results. Generally, at-home or POCT tests are not as accurate as testing conducted in the laboratory. Laboratories that conduct alcohol or drug testing are usually accredited, which means they have to work to very strict regulations to ensure the work is carried out to the highest standards, and that all results are extremely accurate.

What type of alcohol tests are there?

There are several different ways that alcohol can be measured or detected, depending on the type of sample that is provided. In this section, we look at some of the different alcohol tests available.


There are two main biomarkers of alcohol that can be tested for in hair. 

Ethyl glucuronide (EtG) is a direct metabolite of ethanol, the active ingredient in alcoholic beverages. EtG is incorporated into our hair mainly through sweat. 

Fatty acid ethyl esters (FAEE) are made in the blood. They are incorporated into the hair via sebum. 

Determining whether someone is using alcohol chronically is best done when EtG and FAEE are assessed together and alongside blood tests. This is because EtG and FAEE can potentially be affected by hair washing or the use of some hair products like hairspray. 

Since both EtG and FAEE are found along the length of the hair, you can’t get a segmented or month-by-month analysis like you can with hair strand analysis for drugs. You can, however, get up to a 6-month overview of alcohol consumption from head hair and up to a 12-month overview from body hair.


You can detect alcohol in the blood using various tests. 

Alcohol in the blood can be detected for around 12 hours after your last drink. A simple blood alcohol test is sometimes used if an offender is caught drink-driving and meets the criteria for a blood test. This type of test will only tell you how much alcohol is circulating in the blood at the time of test.

However, there are other types of blood tests that can show someone’s drinking patterns over a longer period of time. These include phosphatidylethanol (PEth), carbohydrate deficient transferrin (CDT), liver function test (LFT) and mean corpuscular volume (MCV) tests.

PEth is a direct marker of alcohol. It relies on the presence of ethanol for its formation, so PEth is only present when you drink alcohol. It can provide an overview of alcohol consumption of up to four weeks. It can determine chronic, moderate, or low alcohol consumption/abstinence. 

To learn more about PEth testing for alcohol consumption, visit our PEth alcohol testing page

Transferrin is a type of protein that helps carry iron to the bone marrow, so it is involved in the manufacture of red blood cells. People who drink excessively make more carbohydrate deficient transferrin (CDT) than those who drink moderately or not at all. The test can therefore distinguish between people who are chronic alcohol drinkers and people who abstain from drinking or drink in moderation. 

A liver function test measure enzymes that are produced by the liver. Drinking alcohol to excess causes problems with the liver, and in turn changes the amount of some of the enzymes that are made in the liver. Abnormal levels of these enzymes are an indicator of alcohol abuse. 

Mean corpuscular volume (MCV) is the average size of red blood cells. When you drink excessively, the red blood cells become larger than normal. Elevated MCV is indicative of alcohol dependency.  However, there are some medical conditions which can also cause red blood cells to enlarge. MCV is therefore more useful when tested alongside PEth, CDT and LFT.

For more information on the blood tests we offer at AlphaBiolabs, visit our alcohol blood testing page


Although the liver is able to breakdown most of the alcohol we drink, about 5% is eliminated through sweat, breath and urine. 

Some urine tests are able to detect alcohol in the urine for up to 4 days after consumption, but this depends largely on the type of urine test used. 

The format of an alcohol urine test is often a cassette – a device similar to a pregnancy test or a Covid-19 antigen test. It can tell you whether alcohol is present in the urine.

Results for these types of tests are usually very quick. However, they cannot distinguish between types of drinkers, and they do not give a quantitative (numerical) result. 

They are good in environments where you need to find out the result quickly or are looking to find out whether someone has recently drunk alcohol. 

Saliva / oral fluid

Recent alcohol use can also be detected using saliva or oral swabs. Depending on the kit used, alcohol in the saliva can be detected around 10-24 hours after consumption, but some kits are able to detect alcohol in saliva for up to 48 hours after drinking. 

The swab is placed in the individual’s mouth and becomes saturated with their saliva. This is then placed into the testing pot. Lines on the results panel indicate whether alcohol is present in the saliva.

Like urine alcohol tests, saliva alcohol tests are only good for detecting the presence of alcohol from recent consumption. 

Saliva or oral fluid tests often come as a drug and alcohol panel, so are a good choice if you are looking to identify recent drug and alcohol use with instant results. 

However, saliva or oral swab tests cannot tell you if someone is binge drinking or dependent on alcohol. They will only tell you if someone has recently consumed alcohol.


In general, a breathalyser will detect alcohol for up to 24 hours after your last drink. 

When someone exhales into a breathalyser, the alcohol is involved in a reaction which produces an electrical current. The electrical current is proportionate to the amount of alcohol in the breath. 

Breathalysers are most commonly used by the police when someone is suspected of drink-driving. They can give a blood alcohol content (BAC) reading very quickly. The legal alcohol limit in Ireland is 22 micrograms of alcohol per 100 millilitres of breath.

Breathalysers might also be used by some employers as part of a routine employment alcohol screen.

What medications can cause false positive alcohol test results?

While false positive alcohol readings are extremely rare, they can sometimes happen.

Alcohol is found in things other than your favourite tipple, such as mouthwash, hand sanitiser or even some medications. 

If you need to prove abstinence, or show that you do not drink excessively, you should consider taking a test that covers multiple markers and sample types, as this will eliminate the chances of you obtaining a false positive result. 

At AlphaBiolabs, we offer a combined blood and hair alcohol testing package, giving you complete insight into someone’s alcohol use. 

Let’s look at some everyday items which contain alcohol. 

Over the counter medications

Over the counter (OTC) medications are medicines which don’t require a prescription from the doctor. 

Some medications, both over the counter and prescribed, contain small amounts of alcohol. 

When you take these medicines, particularly if you need to take the maximum dose, some of the alcohol will circulate in your blood. 

Some people buy certain OTC medicines to abuse them because of their alcohol content. Whilst some prescribed medications also contain alcohol, they can only be obtained through a prescription and so are harder to obtain.

Why is alcohol in medicines at all? Depending on the medicine, alcohol might be used as a preservative or as an active ingredient. You’re more likely to find higher alcohol concentrations in liquid medicines. 

Some medicines that contain alcohol include:

  • Some cough medicines (e.g. Sudafed)
  • Some cold and flu medicines (e.g. Tylenol) 
  • Some allergy medications (e.g. Benedryl)
  • Vicks 

If you need to take medicines that contain alcohol, you should avoid having alcoholic drinks at the same time. Not only will the dual consumption of alcohol increase your BAC, but some medications can interact badly with alcohol and can have serious consequences. 

Asthma medications

Asthma is a condition that causing breathing difficulties. It’s relatively common and is usually treated with steroid inhalers. 

Some steroid inhalers contain alcohol. One example is beclomethasone inhalers. 

Alcohol is sometimes used in inhalers because it increases the solubility of the active ingredient. This helps it to work faster and more effectively. 

As the delivery method involves you breathing the medicine into your lungs, there is a small chance that you may get a slightly higher BAC reading from a breathalyser. 


Alcohol is usually present in mouthwash. 

Depending on the brand, alcohol may be used to make the ingredients more soluble. 

The alcohol that remains in the mouth after you spit the mouthwash out can potentially lead to false positive results from a breath or saliva test.

Oral gels

Some oral gels like the ones used to treat mouth ulcers may contain a very small amount of alcohol.

How can I avoid false positive alcohol test results?

Despite the presence of alcohol in the medications listed above, getting a false positive on an alcohol test is extremely rare, as you should not be consuming these products in the same quantity as you would an alcoholic drink, and the alcohol levels will also be significantly lower than those contained in alcoholic drinks.

However, if you are required to submit a sample of any kind for an alcohol test, you should always tell the sample collector if you have recently used any medicine or products that contain alcohol. 

The sample collector will gather this information and it will be factored into the results to ensure that they are a true reflection of your recent or past alcohol consumption. 

Unless you are abusing over the counter medicines or alcohol-containing products, a breathalyser is extremely unlikely to give a reading that is indicative of intoxication, and other tests for longer-term alcohol use will not indicate excessive or chronic use.

Where can I get an alcohol test?

AlphaBiolabs is one of Ireland’s leading providers of laboratory alcohol testing services for members of the public, the legal sector, and the workplace sector.

Our accredited laboratory can test a variety of samples for the presence of alcohol and its metabolites, including breath, blood, hair, and nails.

We also offer alcohol monitoring in the form of SCRAM Continuous Alcohol Monitoring®.

To discuss your alcohol testing needs, call our Customer Services team on 01 402 9466 or email

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Liz Wood AlphaBiolabs

Liz Wood

Health Testing Specialist at at AlphaBiolabs

Liz joined AlphaBiolabs in 2021, where she holds the role of Health Testing Specialist.

As well as overseeing a range of health tests, she is also the lead on several validation projects for the company’s latest health test offerings.

During her time at AlphaBiolabs, Liz has played an active role in the validation of the company’s Genetic Lactose Intolerance Test and Genetic Coeliac Disease Test.

An advocate for preventative healthcare, Liz’s main scientific interests centre around human disease and reproductive health. Her qualifications include a BSc in Biology and an MSc in Biology of Health and Disease.

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