The interest in CBD oil as a natural remedy is huge, with up to 6 million people in the UK alone having tried it, and it’s only growing. But what exactly is CBD oil? What are the potential benefits – and side-effects – and what research is there to back them up? Is it safe? And what does the law have to say about this cannabis-derived product?


CBD – or cannabidiol – is an extract of the cannabis sativa plant used as a natural remedy for a wide variety of ailments. It’s one of numerous different compounds known as cannabinoids that are present in cannabis and is the second most common after THC, the substance that gets marijuana smokers stoned. However, CBD is usually extracted from low-THC strains of cannabis called hemp and won’t get you high.

CBD comes in a range of products. CBD oil, mixed with a base oil such as hemp seed or olive, is taken orally – either directly as droplets, in food and drink or sublingually (under the tongue). CBD also comes in capsules, chewable gummies, topical creams and in e-liquids that are inhaled using a vaping device.

According to recent studies, between 4 and 6 million people in the UK – from wide range of age groups and backgrounds – have tried CBD in some form, while a 2019 poll in the US found that 14% of Americans had used CBD.


There are currently two CBD-based medications available by prescription on the NHS, for those suffering from specific conditions where other treatments have been ineffective.

Epidiolex, which contains pure CBD, can be used to treat two rare types of epilepsy called Dravet syndrome and Lennox-Gastaut syndrome.

Nabiximols, brand name Sativex, contains a combination of CBD and THC and can be given to people with multiple sclerosis who are suffering from spasticity, a tightening or stiffening of the muscles that affects movement and speech. Studies are also ongoing into the drug’s effectiveness in treating certain cancer-related symptoms.

According to UK law, companies selling CBD products cannot currently make medical claims about them (so it is best to steer clear of any brands that do this). Instead, they are advertised as food supplements. However, CBD is generally considered to be safe for people in non-vulnerable groups.


Interest in CBD, from the point of view of both users and researchers attempting to understand its effects on various medical conditions, is often related to the fact that it has few serious side-effects. CBD is generally considered ‘well tolerated’ by clinicians, meaning it is rare for patients to opt out of studies involving CBD as a result of adverse effects.

However, there are a number of low-level side-effects sometimes associated with CBD. One large study of CBD users published in 2018 found that dry mouth was the most common, experienced by 11% of those surveyed. Tiredness or fatigue are also regularly reported, and CBD can sometimes cause appetite changes, irritability, nausea and diarrhoea.


Many of CBD’s effects on the human body are thought to be related to its interactions with the Endocannabinoid System (ECS), which regulates internal states including mood, immune responses, inflammation and pain.

The ECS consists of three main elements:

  • cannabinoid receptors, CB1 and CB2, present in cells around the nervous system
  • endocannabinoids
  • enzymes

Endocannabinoids are molecules produced on-demand by the body. They bind to cannabinoid receptors, signalling them to take actions, such as produce an immune response. Enzymes then break down the endocannabinoids.

Although plant cannabinoids (phytocannabinoids) like CBD and THC don’t interact with cannabinoid receptors in precisely the same way as endocannabinoids, they do influence them.

THC binds to both CB1 and CB2 receptors and can have multiple effects, positive and negative, including those that anyone who has smoked marijuana will be familiar with.

CBD’s interactions with the ECS appear to be more subtle, including moderating the effects of THC itself (for instance, by reducing its intoxicating qualities). It’s also thought that CBD may prevent endocannabinoids from being broken down, thereby prolonging their effects. This could explain how it is able to help with pain relief and stress-related complaints such as anxiety. Meanwhile, some researchers believe that CBD could bind to an as yet undiscovered endocannabinoid receptor.

CBD may also owe some of its therapeutic effects to its interactions with receptors outside the ECS. These include opioid receptors involved in pain relief, TRVP1 receptors which produce the sensation of scalding heat and 5-HT receptors that bind with the mood regulator serotonin.


As discussed, side-effects of CBD are relatively rare and usually minor. In terms of its general safety, the World Health Organization considers CBD to have “a good safety profile”, while the European Union’s court of justice says that it “does not appear to have any psychotropic effect or any harmful effect on human health”.

Due to the ongoing nature of research into CBD, the UK’s Food Standards Agency advises as a precaution that people in vulnerable groups, such as pregnant and breastfeeding women and those taking medication, do not use CBD and that healthy adults do not take more than 70mg a day (approximately 28 drops of 5% strength CBD oil), unless advised by a doctor.

If you are considering using e-liquids containing CBD you should be aware of the “serious risks” said to be associated with vaping itself.

There is also reason to be cautious regarding CBD’s potential interactions with some medications.


If you are taking medication or supplements, you should not use CBD without first consulting your doctor. That’s because it can inhibit the breakdown of certain drugs, potentially leading to unsafe levels in the body.

Grapefruit and some other citrus fruits can have the same effect, so you may be advised to avoid taking CBD with medications that carry a ‘grapefruit warning’. These include some statins (used to control cholesterol) and blood pressure medicines.

However, CBD may also affect the metabolisation of drugs that do not come with a warning.

Therefore, if you are on any medication, you should not take CBD without talking to your doctor. Similarly, you should not stop using prescribed drugs without seeking medical advice.


The short answer is no, CBD itself doesn’t get you high. Instead, the stoned feeling associated with smoking cannabis is caused by the psychoactive cannabinoid THC.

Brands that process their hemp correctly and abide by government guidelines generally have no more than trace amounts of THC in their products. Although a recent study of CBD products available in the UK found that almost half contained measurable levels, these averaged just 0.04% THC, not enough to produce any intoxicating effects.


Although it is extracted from cannabis plants, in its pure form CBD is not a controlled substance in the UK, meaning it is legal to buy products containing it. However, THC is illegal and, depending on the raw ingredients and processes used to make CBD products, may still be present in some of them. There are therefore strict limits to the levels of THC allowed in both plants grown in the UK and CBD products sold here.

The Home Office licences producers to grow strains of hemp that contain no more than 0.2% THC based on their dry weight when harvested.

In the majority of European countries, 0.2% also happens to be the legal limit of THC in CBD products themselves, while in the United States it is 0.3%. However, in the UK, the approach is different. Here, THC in CBD products is measured not as a percentage but by weight, with any single packet or container, regardless of its size, allowed to contain no more than 1mg of THC.

That means that the legal percentage of THC in, for example, bottled CBD oil varies depending on its volume: while a 30ml bottle containing 1mg of THC would be 0.003% THC, a 10ml bottle with the same amount would be 0.01% THC.

Given that 10ml is generally the smallest volume of CBD oil available, 0.01% is effectively the legal limit of THC.

Currently, these limits are not always followed. A 2018 investigation testing CBD products available on high streets and online in the UK found that almost half exceeded this. While THC levels in these products averaged only 0.04%, they are still technically illegal.

However, issues like this are likely to be resolved over the course of 2021, with the implementation of new regulations around the sale of CBD products in the UK.


In January 2019, the UK’s Food Standards Agency announced that it was classifying CBD products as so-called Novel Foods. The European Union has since followed suit.

Novel foods are foods which have not been widely consumed by people in the UK or the EU before May 1997, when the classification first came in. This means the foods don’t have what the FSA calls “a history of consumption”.

Before a Novel Food can be legally marketed in the UK it must go through a safety and authorisation process that requires producers to provide a dossier of information for each of their products demonstrating that they are fit to be sold under the classification. During this period, no new CBD products can be brought to the UK market.

The Novel Foods process for CBD ends in the UK on 31st March 2021, after which only products which have met its criteria will be allowed to be sold here. This is good news for consumers, ensuring that products contain the levels of CBD they claim to and no more than the legal limits of THC and other substances. However, it will only favour manufacturers whose products are up to scratch and able to demonstrate their provenance and quality.


If you’ve read the earlier sections of this article, you may well have gathered by now that the three letters CBD don’t actually stand for words. Instead they are a shortened version of the single word cannabidiol. Confusingly, cannabidiol is itself a cannabinoid, one of the many compounds along with THC found in cannabis and hemp plants. It’s also not to be confused with cannabis oil, which is a resinous form of marijuana – although cannabis oil does contain cannabidiol/CBD.


CBD can be consumed in a variety of formats but perhaps the most popular products are bottled oils, which combine CBD with a carrier oil such as hemp seed, olive or coconut. Good CBD oil brands come with an integrated dropper in the cap so that measured doses can be easily administered directly into the mouth or added to food and drink.

The most efficient and effective way to take CBD oil is by ‘sublingual’ application – placing droplets of the oil beneath the tongue and holding them there for a few moments before swallowing. This allows the CBD to enter the bloodstream quickly due to the density of capillaries there and leads to a greater degree of absorption.

Many people enjoy consuming CBD oil in drinks, with CBD coffee an on-trend option. However, there is evidence that CBD in a solution can degrade when exposed to heats above 71°F so if you like your coffee hotter than lukewarm it’s possible you may be consuming less CBD than you think.

CBD oil can also be added to food after it has been prepared, however the process of digestion not only slows down the absorption of the CBD but also destroys more of it than sublingual application. If you do decide to take CBD with food, it’s worth being aware of research suggesting that CBD is better absorbed when accompanied by higher-fat foods.

The caveats about ingesting CBD also apply to CBD soft gels, capsules or chewable gummies. They can be a convenient way of taking CBD and contain a measured dose, however varying amounts are likely to be lost during digestion.

CBD can also be administered through creams and cosmetics applied to the skin. Most creams are known as topical, meaning they do not penetrate beyond the upper layers of the skin. However, there are cannabinoid receptors in the skin and there is initial evidence that topical CBD creams may help with localised complaints such as arthritis.

Finally, electronic vaping devices are a popular way to consume CBD in the form of e-liquids. Because the vapours are inhaled directly into the lungs, vaping CBD provides the fastest and most efficient assimilation into the body. However, there are serious safety concerns over vaping itself, so this is a method you may want to think twice about.


Once you’ve decided which method of CBD consumption might best suit you, you need to consider how much to take. The ideal dosage can vary from person to person based on a number of factors including age, weight, the particular condition they wish to treat, their own specific reactions to the CBD and the way they plan to take it.

A recommended approach is to start with small doses, as low as 5-10mg per day, and to work your way up in similar increments. The aim is to find the smallest amount of CBD that has the desired result and does not elicit any unwanted side-effects. It’s worth taking each dosage for a few days before you increase it, to give your body time to respond, and it’s useful to keep a diary of how you feel afterwards (remember, the effects may be subtle). If you experience any unwanted side-effects, reduce the dosage.

See the section below to find out how to calculate the amount of CBD in a single drop of oil, based on its strength by percentage.