CBD side effects are described, but mainly from clinical studies with pharmaceutical-grade CBD in high amounts: most commonly fatigue, diarrhoea, altered appetite and abnormal liver values. For over-the-counter products, robust data is lacking, which is why the BfR and EFSA have explicitly left their assessment open.
This article puts the position of the authorities and the main reviews into factual context. It makes no effect or usage promises and gives no dosage figures, but shows what is known, where the findings come from and where the limits of the data lie.
CBD side effects at a glance: what authorities and studies describe
Cannabidiol is a non-intoxicating cannabinoid of the hemp plant that is pharmacologically active. From its use as a medicinal product it is known that CBD can cause unwanted effects, at least at higher intake amounts. The German Federal Institute for Risk Assessment names a sedating effect and impaired liver function as examples and points to a potential for interactions with other medicinal products.
Studies and reviews mainly describe these unwanted effects:
- fatigue, drowsiness and sedation
- diarrhoea and other gastrointestinal complaints
- reduced appetite and changes in weight
- altered liver values, predominantly together with other medications
- interactions with medications broken down via the same liver enzymes
According to the BfR, whether these effects also play a role at the low amounts found in products from retail cannot currently be assessed. This is exactly the core of the debate: most findings come from studies with an approved medicinal product, not from investigations of flowers, hash or CBD oils as offered on the market.
Regulatory position: BfR, EFSA and WHO compared
Three bodies shape the assessment in Germany and Europe. Their statements differ in perspective, not in the basic finding: CBD is not risk-free, and for food the data is not sufficient.
| Body | Document | Key statement on unwanted effects |
|---|---|---|
| BfR | Questions and answers, 2022 | sedation, impaired liver function and interactions known from medicinal use; relevance at low amounts open |
| BfR | Communication 035/2024 | considerable knowledge gaps regarding the liver, gastrointestinal tract, hormonal system and nervous system |
| EFSA | Statement, 2022 | safety of CBD as a novel food cannot be assessed, data gaps named |
| WHO ECDD | Critical Review Report, 2018 | generally well tolerated; reported effects partly due to interactions with medications |
BfR: medicinal experience is not the same as a food assessment
The BfR clearly distinguishes between what is known from medicinal use and what can be said for food. In its 2024 communication, it states that the data on the effects of CBD on the liver, gastrointestinal tract, hormonal system and nervous system are not sufficient for a conclusive assessment.
EFSA: assessment as a novel food suspended
The European Food Safety Authority stated in 2022 that the safety of CBD as a novel food cannot be assessed with the available data. It names open questions regarding the liver, gastrointestinal tract, hormonal and nervous system as well as psychological functions, and states that studies with the approved medicinal product cannot readily be transferred to food.
WHO ECDD: assessment of tolerability and dependence
The World Health Organization's expert committee concluded in 2018 that cannabidiol is generally well tolerated and shows a good safety profile. Reported unwanted effects could, according to this, partly be due to interactions between CBD and already prescribed medications.
What reviews summarise about unwanted effects
A 2020 meta-analysis, according to the authors the first across all fields of application, summarises twelve placebo-controlled studies with 803 participants. Compared to placebo, reduced appetite, diarrhoea, drowsiness and sedation occurred more often under CBD, as well as abnormal liver values.
Liver values: where the finding comes from
The liver finding is the most frequently cited point. The meta-analysis shows that abnormal liver values, drowsiness and sedation were confined to studies on childhood forms of epilepsy in which CBD was given together with other antiepileptic drugs. When the authors excluded these studies, the only remaining statistically significant effect was diarrhoea. A further review from 2019 likewise describes liver abnormalities, diarrhoea, fatigue, vomiting and drowsiness from studies in humans, and concludes that CBD is not risk-free.
What the studies do not cover
Both papers point to a gap: safety data from studies outside epilepsy treatment and on over-the-counter products are lacking. The findings come predominantly from high, medically supervised amounts of a medicinal product. How this can be transferred to products from retail remains scientifically open.
Interactions with medications: described by the EFSA and reviews
Cannabidiol is broken down via liver enzymes and at the same time influences these enzymes. Many medications are metabolised via the same pathways. A 2019 review therefore rates the potential for interactions with common medications as high, and the EFSA also lists interactions among the open questions. The BfR describes that taking CBD at the same time can weaken or strengthen the effect of other medicinal products.
Anyone taking medication should therefore clarify questions about CBD with a doctor or pharmacy beforehand. This applies especially with several medications, during pregnancy and breastfeeding, and with existing conditions. A general guide cannot replace this individual assessment.
Psyche and intoxication: what the WHO states
A frequently searched question is whether CBD alters the psyche or is addictive. The WHO found no evidence of abuse or dependence potential in humans. According to this assessment, cannabidiol does not trigger a high the way THC does; the difference lies in the very low binding to cannabinoid receptors described by the BfR. What cannabidiol is as a substance and how it differs from THC is explained in the basics article What is CBD.
Drowsiness and sedation, on the other hand, are among the described unwanted effects, and the EFSA explicitly names psychological functions and the nervous system among the areas with data gaps.
Why study data and products from retail diverge
Three factors explain why study findings cannot be transferred one to one to a product: the amount, the composition and the accompanying substances. Studies work with a precisely defined medicinal product. Products from retail differ in cannabinoid profile, carrier oil and THC content.
How large these differences can be is shown by a 2024 BfR investigation: in 20 of 26 tested cannabinoid oils, the institute detected Δ9-THC, and while manufacturers declared CBD, CBG and CBN contents of between 2.5 and 20 percent, the measured values ranged from 3 to 24 percent. Unwanted effects of a product can therefore also depend on the THC content, not only on the CBD. How oils differ by spectrum, carrier oil and lab values is shown in the article on the effects of CBD oils.
This is why transparency about the actual composition is decisive. At CBDÍA, a publicly viewable laboratory certificate is available for every batch, stating CBD, THC and other cannabinoids; this is supplemented by origin with country and cultivation type as well as varieties from the EU variety catalogue. This is information about composition, not a statement about tolerability. What research describes overall about the effect of cannabidiol is summarised in the article on CBD effects.
Legal framework and Novel Food
CBD is not listed in any schedule of the German Narcotics Act and is excluded from the definition of cannabis under the German Consumer Cannabis Act. As a food, CBD is not approved in the EU: the European Commission classifies it as a novel food, and no corresponding product has been approved to date. More on the classification of hemp and flowers is in the article Legal status of CBD flowers. Not legal advice, as of: September 2026.
In brief
Described are mainly fatigue, diarrhoea, altered appetite, abnormal liver values and interactions with medications, predominantly from studies with high amounts of a medicinal product. The BfR and EFSA see considerable data gaps, while the WHO attests a generally good safety profile without dependence potential. For products from retail, the data is thin; only a batch's laboratory certificate shows what it contains. Sale only to adults aged 18 and over.
This article is for general information purposes only and does not replace medical advice. As of: September 2026.
