CBD side effects: what the science says, dose by dose

The starting point is a matter of consensus. In its 2018 critical review report on cannabidiol, the WHO expert committee concludes that pure CBD is “generally well tolerated, with a good safety profile”, and that it presents no abuse or dependence potential. The report notes that doses of up to 1,500 mg per day have been well tolerated in humans.

That reassuring finding has a flip side: it relates to precise study conditions. “Well tolerated” does not mean “with no effect at all”, and certainly not “suitable for everyone”.

The adverse effects observed are mostly mild to moderate. A systematic review published in Current Neuropharmacology in 2023 lists the most frequent: diarrhoea, drowsiness or sedation, and reduced appetite. These effects are dose-dependent: they increase as the oral dose rises.

In practice, this means that an effect that is felt is not abnormal in itself, but that it deserves attention. In the event of marked drowsiness, it is better to avoid driving, and to adjust the timing of intake. As always, listening to your own experience comes first — a theme we cover in what the clinical studies really say about CBD.

This is the most important point for safety. CBD strongly inhibits certain liver enzymes, CYP3A4 and CYP2C19, which are involved in the metabolism of many medicines. The 2023 review links this inhibition to clinically relevant interactions, such as increased drowsiness with clobazam or a rise in liver enzymes with sodium valproate.

The rise in transaminases is likewise dose-dependent and concentrated at pharmaceutical doses: in a study in healthy volunteers at 1,500 mg per day, 44% showed a peak above the normal range. These signals concern doses that bear no relation to ordinary use, but they impose a simple rule: if you are taking any medication, discuss it with your doctor or your pharmacist before using CBD at all. Our dedicated article sets out CBD, liver enzymes and interactions in detail.

Much of the confusion comes from the dose. The fullest evidence base comes from the trials of Epidyolex, a medicine for certain epilepsies, dosed at up to 50 mg per kilo per day — around 3,500 mg for a 70 kg adult. That is an order of magnitude with no common measure with wellbeing use.

The clearest liver and interaction signals therefore reflect a high-dose medicine, not ordinary consumption. Confusing the two leads either to excessive worry or, conversely, to crediting the product with an efficacy it does not have. Over-the-counter CBD is not a medicine and cannot claim any therapeutic effect.

In February 2026, the European Food Safety Authority took a step forward. It published a provisional safe level for cannabidiol as a novel food set at 0.0275 mg per kilo of body weight per day — around 2 mg per day for a 70 kg adult, once an uncertainty factor is applied.

EFSA also states that the safety of CBD cannot be established for people under 25, for pregnant or breastfeeding women, or for people on medication. This milestone sheds direct light on the withdrawal of ingestible CBD products from the French market, in force since 15 May 2026: a food-safety measure, which we set out in our update on CBD and the Novel Food regulation.

Is CBD dangerous to health?

The WHO describes it as well tolerated, with a good safety profile and no abuse potential. The side effects that are documented are mostly mild. The more serious signals, liver-related or interaction-related, appear at high pharmaceutical doses, with no relation to ordinary use.

What are the side effects of CBD?

The most frequent, according to a 2023 review, are diarrhoea, drowsiness or sedation, and reduced appetite. They are dose-dependent and generally mild. In the event of marked drowsiness, it is prudent to avoid driving and to adjust the timing of intake.

Is CBD bad for the liver?

CBD may raise liver enzymes, but in a dose-dependent way and above all at high pharmaceutical doses. It also inhibits liver enzymes involved in the metabolism of medicines. If you are taking any medication, seek the advice of a doctor or a pharmacist.

Can you take CBD at the same time as medicines?

That is the question to put to a healthcare professional. CBD inhibits the CYP3A4 and CYP2C19 enzymes, which may alter the effect of certain medicines. EFSA also points out that the safety of CBD is not established for people on medication.