5 Types of Medication That Can Affect Breathalyser Results

You might have heard before that certain medications can interfere with a breathalyser result. It’s one of those claims that gets repeated quite often, usually without much explanation of what it actually means or how likely it is to happen.

The reality is a little less dramatic. Most everyday medications won’t have any effect on an alcohol breath test, but there are some types of medicine that can contain ethanol. If they’ve been taken shortly before a breath test, that alcohol can potentially be picked up in the mouth.

At Intack Self Drive, as well as offering the very best daily hire and flexi hire vehicle services, we also like to clear up some of the questions and misconceptions that come up around driving.

So, if you’ve ever wondered whether medication can really affect a breathalyser, here’s what’s actually worth knowing.

1. Cough medicines and syrups

Cough medicines are probably one of the most commonly mentioned examples when this topic comes up, and there is some truth behind it. Certain liquid cough syrups contain ethanol as part of their formulation, often because it’s used as a solvent or to help dissolve other ingredients within the medicine.

That doesn’t mean every bottle of cough medicine contains alcohol, and it also doesn’t mean taking one will automatically result in a positive breathalyser reading. The important thing is the individual formulation. Two medicines designed to treat a similar cough can contain completely different ingredients, so it’s always worth checking the label or patient information leaflet if you’re unsure.

Where ethanol is present, a small amount can remain in the mouth for a short period after taking the medicine, which is where the potential for interference comes from. In other words, it isn’t necessarily the active cough medicine itself causing the issue, but the alcohol included in the liquid preparation.

2. Cold and flu medicines

Some liquid cold and flu remedies can work in much the same way. These products often combine several different ingredients to tackle symptoms like headaches, congestion, sore throats, and coughing, and certain formulations may also contain ethanol.

Again, it’s easy to assume that the medication itself is somehow confusing the breathalyser, but that isn’t really what’s happening. If alcohol is included in the medicine, the device may simply detect traces of that alcohol shortly after you’ve taken it.

There’s another thing worth keeping in mind with cold and flu medication too. Some products can make you feel drowsy, dizzy, or less alert, which is a separate issue from breathalyser readings altogether. Even if a medicine contains no alcohol at all, you should still pay attention to any warnings about driving and avoid getting behind the wheel if you don’t feel fully alert.

3. Liquid antihistamines

Antihistamines are another category where the formulation matters. They’re commonly used for allergies, hay fever, itching, and other conditions, and while most people are familiar with the ones that come in tablet form, some are also available as liquids.

Certain liquid antihistamines can contain ethanol, which means they can fall into the same category as cough and cold medicines when it comes to breath testing. That said, this won’t apply to every product, so it’s much more useful to check the actual ingredients than to assume all antihistamines are a problem.

Again, like some cold medicines, certain antihistamines can cause drowsiness. So, even where there is no alcohol in the medicine, it’s still important to follow the instructions on the packaging and be aware of how the medication affects you before driving.

4. Medicated throat sprays and oral treatments

Some medicated throat sprays, gargles, and oral treatments can also contain ethanol. As these products are used directly in the mouth and throat, however, they are slightly more relevant when talking about temporary traces of alcohol being left behind after use.

This is also where the phrase “false positive” can become a little misleading. If a product contains alcohol and some of that alcohol is still present in the mouth, a breathalyser detecting it isn’t necessarily making a mistake. It may simply be detecting alcohol that is genuinely there at the time of the test.

For most drivers, this isn’t something to worry about if you happen to have a sore throat. It just helps explain why certain throat medicines can occasionally be mentioned in conversations about breathalyser results, especially when they’ve been used very recently before testing.

5. Herbal medicines and tinctures

This is one most people don’t expect. Herbal medicines can be easy to overlook because they don’t always feel like the kind of product that would contain alcohol, but some liquid herbal remedies and tinctures use ethanol as part of the extraction or preservation process.

That means a herbal product can potentially contain alcohol in the same way as some conventional liquid medicines. As with everything else on this list, though, it depends entirely on the individual formulation.

The word “herbal” doesn’t automatically mean alcohol-free, just as conventional medicine doesn’t automatically contain alcohol. If you’re taking a liquid remedy and want to know what’s in it, the packaging and patient information leaflet are the best places to look.

So, can medication really cause a false positive?

This is the main misconception worth clearing up.

When people hear that medication can affect a breathalyser, it can sound as though the device is somehow mistaking a completely unrelated drug for alcohol. In reality, the issue is usually much simpler than that. Some medicines contain ethanol, and if traces of that alcohol are still present in the mouth, a breathalyser may be able to detect them. So, calling it a “false positive” isn’t always quite accurate. The machine may be detecting genuine alcohol, just not necessarily from an alcoholic drink.

It’s also important to stress that most medicines won’t have this effect at all. Tablets, capsules, and many alcohol-free liquid formulations are unlikely to have any bearing on an alcohol breath test, which is why this is much more about understanding specific ingredients than worrying about medication in general.

How long can medication affect a breathalyser?

There isn’t a single answer that applies to every medicine, because it depends on the product, the amount of alcohol it contains, how it is taken, and how recently it was used.

The main concern is usually alcohol remaining temporarily in the mouth rather than the medicine somehow creating a lasting alcohol reading in the body. That’s also why it wouldn’t make sense to rely on a set waiting time as a way of deciding whether you are safe or legal to drive.

If you are taking a medicine regularly, checking the ingredients and any driving warnings in the patient information leaflet is the simplest way to understand whether there is anything you need to be aware of.

What happens if you’re breathalysed by the police?

It’s worth remembering that a roadside breath test is a screening test rather than the whole process by itself. If a driver fails a roadside breathalyser, there are further procedures in place, which can include evidential breath testing.

If you have recently taken medication that you think could be relevant, you can make the police aware of what you have taken. That doesn’t mean medication gives you an exemption from drink-driving laws, but it does mean there is more context around a breath test than many people realise.

The most important thing is not to assume that medication will explain away a positive reading, or that taking medicine means you are automatically safe to drive. Alcohol content is only one part of the picture, and some medicines can affect your ability to drive safely even if they have no impact on a breathalyser whatsoever.

What you actually need to know about medication and breathalysers

For most people, there’s no reason to worry about everyday medication interfering with a breathalyser. The idea isn’t completely made up, but it is often presented in a way that makes it sound much more common than it really is. In reality, the chances of finding yourself in this situation are relatively slim, and most medicines won’t have any effect on an alcohol breath test at all.

The main medicines worth being aware of are certain liquid cough and cold remedies, liquid antihistamines, medicated oral treatments, and herbal tinctures that contain ethanol. Even then, not every product in those categories contains alcohol, and taking one doesn’t mean you’re going to fail a breath test, which is why checking the individual formulation matters.

There are also procedures in place to account for things that could interfere with an evidential breath test. If you’ve recently taken medication that you think may be relevant, you can tell the police what you’ve taken so it can be taken into consideration as part of the testing process. So, if you’ve taken your medicine as directed, followed any warnings about driving, and aren’t impaired, an unusual roadside result isn’t necessarily the end of the matter.

So, while there is a little bit of truth behind the idea that medication can interfere with breathalyser results, it isn’t something you need to be overly concerned about. It’s just useful to know why it can happen and what to be aware of if you ever find yourself in that situation!

At Intack Self Drive, we’ll continue to keep an eye on the rules, misconceptions, and everyday driving questions that are worth knowing about, so you can stay informed without getting caught up in unnecessary worry.

And of course, if you ever find yourself in need of a vehicle, whether it’s short-term or something more flexible, we’re always here to help at Intack Self Drive.

Our daily hire and flexi hire options give you access to a wide range of cars, vans, and minibuses, so you can choose what works best for you. If you’ve got any questions or just want a bit of guidance through the hire process, feel free to give us a call on 01254 57811 and we’ll be happy to assist however we can!