CBD

Is CBD safe?

For most healthy adults, a few drops of CBD oil are unlikely to cause harm in the short term. CBD (cannabidiol) does not make you high, and the common side effects are sleepiness, diarrhoea and less appetite. The problems are less visible. CBD can raise liver enzymes, it changes how the body clears several prescription drugs, and the bottle may not contain what the label says.

Regulators have become more cautious, not less. The UK Food Standards Agency cut its advised daily limit for healthy adults from 70 mg to 10 mg in October 2023. In 2026 the European Food Safety Authority set a provisional safe dose of about 2 mg a day for a 70 kg adult, and only for very pure CBD. Many shop products give 20 to 50 mg per serving.

What prescription CBD tells us

The best safety data come from Epidiolex, a purified CBD drug the FDA approved for seizures in Lennox-Gastaut syndrome, Dravet syndrome and tuberous sclerosis complex. Its label is blunt. Doctors must check liver tests before starting. The usual dose is 5 to 10 mg/kg a day, rising to 20 mg/kg (or 25 mg/kg in tuberous sclerosis). In controlled trials, 13% of patients had ALT, a liver enzyme, above three times the normal limit, against 1% on placebo. The risk was much higher in people also taking valproate.

Those are high doses in very ill patients on several drugs. The more useful question is what happens at consumer doses in healthy people, and the FDA paid for a trial to find out. In 2024, 201 healthy adults took CBD at 5 mg/kg a day (about 350 mg for a 70 kg person) or placebo for 28 days. Eight people on CBD (5.6%) had liver enzymes above three times the normal limit, and none on placebo. Seven met the criteria for possible drug-induced liver injuryDrug-induced liver injuryLiver damage caused by a medicine, herbal product or supplement. It is usually rare and unpredictable, but it can be serious.More in the glossary, usually found at day 21 or 28.

That dose is higher than most people take from a shop oil, but well within what some heavy users reach. The trial lasted four weeks, so it says little about years of daily use, which is exactly what the FSA and EFSA worry about. Both also point to thyroid and reproductive effects seen in animal studies.

Drug interactions

CBD blocks or changes several of the liver enzymes and gut transporters that handle medicines. The Epidiolex label lists:

Drug	What happens
Clobazam	Active metabolite rises, more sedation
Valproate	Much higher chance of liver enzyme rises
Everolimus	Exposure up about 2.5-fold; tacrolimus, sirolimus and digoxin may rise too
CYP1A2CYP450 enzymesA family of liver enzymes that break down many medicines. When another drug or supplement speeds them up or slows them down, drug levels change.More in the glossary drugs (theophylline, tizanidine)	Levels may rise
CYP2C19 and CYP2C8 drugs	Dose changes may be needed

Shop doses are lower, but they are not free of interactions. In a 2026 study, 2.5 mg/kg twice a day raised blood levels of the antidepressant citalopram by 43%. Similar drugs such as sertraline are handled partly by the same enzymes. CBD also adds to the drowsiness of zolpidem, alprazolam, other sedatives and alcohol. People on warfarin should only use it with INR monitoring. If you take any regular medicine, talk to your doctor or pharmacist before adding CBD.

Does the bottle contain what it says?

Often not. In a 2017 study in JAMA, researchers bought 84 CBD products online and tested them. Only 31% were accurately labelled. 43% held more CBD than stated and 26% less, and THC turned up in 21%. Oils did better than vape liquids. Later testing keeps finding the problem; a 2026 study of oils sold in Costa Rica, for example, found both over- and under-labelling and possible THC.

THC matters for two reasons: it can cause a failed drug test, and in edibles it can be enough to affect a child. If you buy CBD, choose a product with a recent certificate of analysis from an independent lab for that batch, showing CBD content and THC.

The legal position

In the US, the FDA concluded in January 2023 that CBD cannot be sold as a dietary supplement or added to food under current law, citing possible liver harm, drug interactions and harm to the male reproductive system. It asked Congress for a new pathway with content limits, labelling and a minimum age. Congress has not created one. A November 2025 law instead caps hemp products at 0.4 mg total THC per container, which would remove most full-spectrum CBD oils. It was due to start in November 2026 and was pushed back by a funding bill to December 2026.

In the UK and EU, CBD foods are novel foods that need authorisation. None has been fully authorised. The UK allows products linked to pending applications to stay on sale.

Who should avoid CBD

The FSA and EFSA name the same groups:

• Children and teenagers (EFSA says safety cannot be established under 25).
• Women who are pregnant, breastfeeding or trying to conceive.
• Anyone taking regular medicines, unless their doctor agrees.
• People with liver disease or who drink heavily.

CBD combined with other calming supplements such as melatonin or kava adds to drowsiness, and kava has its own liver warnings.

How we scored it

Product quality (40) and regulatory actions (35) are the weakest factors: labels are often wrong and CBD is not a lawful supplement in the US or an authorised food in Europe. Organ toxicity (55) reflects liver enzyme rises in a well-run trial in healthy adults. CBD scores below St John's wort, which interacts more but is better studied and regulated, and above kava.