What Is CBD? Cannabidiol Explained in Plain Language

What is CBD?

CBD (cannabidiol) is a phytocannabinoid, meaning a cannabinoid made by a plant, in this case Cannabis sativa L. The WHO's 2018 critical review (opens in a new tab) describes it as a 21-carbon terpenophenolic compound. The plant first makes an acid form, cannabidiolic acid (CBDA), which turns into CBD when it is heated, exposed to light or aged.

In medical terms, cannabidiol is also the name of the active substance in the medicine Epidyolex (more on that below). In shops, "CBD" usually refers to an extract or a purified isolate added to oils, capsules, sweets, drinks or cosmetics.

CBD is not new to science. Adams and colleagues isolated it from a cannabis extract in 1940, but its exact chemical structure was only worked out in 1963, by Mechoulam and Shvo (Zuardi, 2008 (opens in a new tab)). Cannabis research picked up in the early 1990s, after researchers described the body's cannabinoid receptors and isolated anandamide, a cannabinoid the body makes itself. Studies on CBD itself only rose sharply in the 2000s.

Where does CBD come from? Hemp, marijuana and hemp seed oil

Hemp and marijuana are both Cannabis sativa. What separates them is how much THC the plant makes. In the EU, farmers can only receive farm subsidies for hemp varieties with no more than 0.3 % THC, a limit that rose from 0.2 % on 1 January 2023 under Article 4(4) of Regulation (EU) 2021/2115 (opens in a new tab). In cannabis varieties bred for fibre, THC is nearly always low and CBD is usually the main cannabinoid (Zuardi, 2008 (opens in a new tab)).

CBD and THC collect in the flowers and leaves. The seeds contain little to no cannabinoids and are mainly a source of fatty acids, as a 2019 clinicians' guide in Mayo Clinic Proceedings (opens in a new tab) explains. That is why hemp seed oil is not the same as CBD oil. A 2020 analysis of commercial hemp seed oils (opens in a new tab) did find some cannabinoids in them, which the authors put down to seeds touching the resin of flowers and leaves during processing.

Source: VanDolah et al., Mayo Clinic Proceedings, 2019 (opens in a new tab).

CBD extracts come in three main types, depending on what is kept from the plant. We explain them in our guide to full-spectrum, broad-spectrum and isolate CBD.

Does CBD get you high? CBD vs THC

No. THC is the compound that produces the "high" associated with cannabis (FDA (opens in a new tab)). The WHO's review found no evidence that oral CBD causes THC-like effects in people. In healthy volunteers, single oral doses of up to 600 mg had placebo-like effects, and in a study of recreational cannabis users, doses of up to 800 mg produced no significant psychoactive or cardiovascular effects (WHO ECDD, 2018 (opens in a new tab)). On that basis, the WHO committee recommended that preparations considered to be pure CBD should not be placed under international drug control (opens in a new tab).

Two practical points:

• Products are not always pure CBD. A 2017 study of 84 CBD products bought online in the US found THC in some of them, at levels the authors said may be sufficient to produce intoxication or impairment, especially among children (opens in a new tab).
• CBD can make you drowsy. The FDA lists drowsiness (opens in a new tab) as one of the side effects of CBD you might notice. If you drive, read our guide on CBD, THC and driving rules in Europe.

How does CBD work in the body?

Your body has its own cannabinoid signalling system, usually called the endocannabinoid system. It includes two receptor types. CB1 receptors sit mainly in the brain and nervous system. CB2 receptors are found mostly on immune cells and in the gut, with low numbers in the brain (WHO ECDD, 2018 (opens in a new tab)). The body makes its own compounds that act on these receptors, such as anandamide.

THC produces the effects that occur when CB1 is activated (opens in a new tab). CBD works differently. According to the WHO review, CBD does not appear to act directly at CB1 receptors (opens in a new tab) and shows low affinity at CB2 receptors (opens in a new tab). It may interact with the endocannabinoid system through indirect mechanisms (opens in a new tab) and act on several other signalling systems. The review adds that it is not yet clear which of these mechanisms lie behind CBD's potential clinical effects (opens in a new tab).

A 2021 pharmacology review by Britch and colleagues (opens in a new tab) lists many biological targets for CBD, including TRPV ion channels and serotonin 5-HT1A receptors. For the approved medicine, the European Medicines Agency notes that the way it works is not clearly understood (opens in a new tab).

After you swallow CBD, the WHO review describes absorption from the gut as erratic (opens in a new tab) and estimates oral bioavailability at about 6 % (opens in a new tab), because the liver breaks down much of the CBD. In lab models, CBD blocks some of the liver enzymes (cytochrome P450) that process other medicines (opens in a new tab); the WHO review notes it is not clear whether this happens at clinical doses (opens in a new tab). Our guide to CBD and drug interactions covers which medicines need caution.

Is CBD a drug or a supplement?

It depends on the product. The same substance can be a prescription medicine, a novel food awaiting approval, or a cosmetic ingredient.

As a medicine. Epidyolex is an oral solution of 100 mg cannabidiol per ml. In the EU it is prescription-only (opens in a new tab) and authorised for patients aged two and over: with clobazam for Lennox-Gastaut syndrome or Dravet syndrome, and with other epilepsy treatments for tuberous sclerosis complex. The EMA based the authorisation on five studies in more than 900 patients. In the US, the FDA has approved only one CBD product (opens in a new tab), the same medicine sold there as Epidiolex.

As a food or supplement. CBD counts as a novel food (opens in a new tab) that needs authorisation before it can be sold as food, EFSA's February 2026 statement says CBD products for oral consumption remain unauthorised (opens in a new tab), and our guide to CBD laws in Europe covers what that means country by country.

As a controlled drug. Pure CBD is not listed in the UN drug control conventions. Cannabis extracts and tinctures are, under Schedule I of the 1961 Single Convention (WHO ECDD, 2018 (opens in a new tab)). How a product is treated in practice depends on its THC content and the country. Our overview of CBD laws in Europe, country by country goes through the details.

What is CBD used for? What research has found

Epilepsy is where CBD research has gone furthest. In clinical trials, a pure CBD medicine was found effective in Lennox-Gastaut syndrome and Dravet syndrome (opens in a new tab), two severe childhood epilepsies that often resist other medication. That medicine is Epidyolex, which the EMA authorised on the basis of five studies in more than 900 patients (opens in a new tab).

Researchers are studying CBD for a range of other uses too. The WHO's 2018 review lists CBD in development for schizophrenia, fragile X syndrome, childhood absence seizures (opens in a new tab) and several conditions in newborns.

Anxiety and sleep have also been studied. In a 2019 case series of 72 adults at a US psychiatric clinic (opens in a new tab), patients took CBD alongside their usual treatment. Anxiety scores fell within the first month in 79.2 % of them and stayed lower for the rest of the study. Sleep scores improved within the first month in 66.7 %, then varied over time. CBD was well tolerated in all but three patients. The study was a chart review without a control group, and the authors call for controlled trials.

For what individual studies tested, at what doses and how they were designed, see our summaries of the research on CBD and anxiety and on CBD and sleep.

Why is CBD so popular?

CBD is easy to buy. The UK FSA describes CBD foods as widely available in shops, cafés and online (opens in a new tab), sold as oils, capsules, sweets, drinks and bakery products.

The best European data on who uses it comes from Germany. In a representative telephone survey of 1,011 people in November 2020 (opens in a new tab), run for the German Federal Institute for Risk Assessment (BfR), 40.2 % had heard of CBD products and 11.4 % had used them. People under 30 were more likely to have used CBD than older age groups.

A follow-up online survey in March 2021 (opens in a new tab) asked 2,000 people who knew of CBD about it, and 26.8 % of them had used it. Among the 535 users, 42.1 % used CBD products at least once a week. The most common forms were oils and tinctures (58.1 %), followed by foods (20.0 %), cosmetics and skin care (17.8 %), flowers (16.6 %), drinks (16.1 %) and capsules or pills (15.1 %). Most users bought online (55.3 %), and others named pharmacies (21.1 %), specialist CBD and hemp shops (20.0 %) and drugstores (19.6 %). The researchers concluded that people are "insufficiently informed" (opens in a new tab) about CBD products and called for better risk communication.

How to read a CBD label and its claims

In the EU, claims on food labels and in food advertising fall under Regulation (EC) No 1924/2006 (opens in a new tab), which has applied since 1 July 2007. The European Commission summarises the aim: claims must be clear, accurate and based on scientific evidence (opens in a new tab), and food bearing claims that could mislead consumers is prohibited. A public EU Register lists which health claims are authorised and which are not. An authorised claim belongs to a specific nutrient or substance under set conditions of use, so a claim authorised for a vitamin in a blend is a claim about that vitamin.

Label accuracy varies between products. A 2018 study of 14 CBD oils sold in Europe (opens in a new tab) found that 9 had CBD levels that differed notably from the label. The 2017 US study of 84 online products found that 31 % were accurately labelled (opens in a new tab) for CBD, 43 % contained more CBD than stated and 26 % contained less. The FDA publishes its warning letters to CBD sellers (opens in a new tab), with letters listed for every year from 2021 to 2025.

When you compare CBD products, these questions help:

1. What exactly is claimed? If the text names a disease or promises an effect on the body or mind, look for that claim in the EU Register. Soft words like "balance" or "calm" can still imply an effect.
2. What kind of study is cited? A controlled trial in people, a case series, an animal study, a cell study and a survey each answer a different question. Check which one a statement refers to.
3. Is there a lab report? A certificate of analysis for the batch, ideally from an independent lab, should show the CBD and THC content.
4. Does the page say who should not take it? A trustworthy page names the groups regulators give advice about, listed in the safety section below.

What forms does CBD come in?

The UK FSA lists CBD foods sold as oils, drops, tinctures and sprays, gel capsules, sweets and confectionery, bakery products and drinks (opens in a new tab). CBD is also sold in cosmetics, vapes and animal products. One of the FDA's open questions is how the route, oral, topical, smoking or vaping (opens in a new tab), changes how much CBD you take in.

Form also affected label accuracy in the 2017 US study: vape liquids were the most often mislabelled and oils the most often accurate (opens in a new tab). For the practical differences between the two most common oral forms, see CBD capsules vs oil.

Is CBD safe? Who should avoid it?

The WHO's 2018 review found CBD generally well tolerated in clinical trials. Adverse events reported in those studies included somnolence, decreased appetite, diarrhoea and fatigue (opens in a new tab). Regulators in the EU, the UK and the US have also published safety advice:

• EFSA (February 2026): for people under 25, pregnant and breastfeeding women and people taking medication, EFSA concluded that the safety of CBD as a novel food cannot be established (opens in a new tab). It also lists data gaps on the liver and the hormonal, nervous and reproductive systems.
• UK FSA: the FSA does not recommend CBD (opens in a new tab) for under-18s, people taking any medication, people trying to conceive, or pregnant or breastfeeding women, unless under medical direction.
• US FDA: CBD can cause liver injury (opens in a new tab), can change how other medicines work, and adds to sedation with alcohol or sedating drugs. Side effects you might notice include drowsiness, diarrhoea, reduced appetite, irritability and agitation.

Our guide to CBD side effects and who should avoid CBD covers the liver findings and the trial doses behind them.

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