CBD safety in humans
Pro Research Analysisby 
Searched over 200M research papers
CBD Safety in Humans: Clinical Data and Common Adverse Effects
Clinical studies consistently show that cannabidiol (CBD) is generally well tolerated in humans, with most adverse effects being mild to moderate in severity. The most frequently reported side effects include diarrhea, somnolence (drowsiness), sedation, tiredness, and changes in appetite or weight. Upper respiratory disturbances and sleep disturbances have also been noted in some cases Madeo2023Iffland2017Larsen2020+4 MORE. Compared to other medications used for similar conditions, such as epilepsy and psychotic disorders, CBD tends to have a more favorable side effect profile, which may improve patient compliance Iffland2017Larsen2020.
Serious Adverse Events and Drug Interactions
Serious adverse events are rare but have been observed, particularly when CBD is used alongside other medications. Notably, elevated liver enzymes (transaminase elevations), abnormal liver function tests, and pneumonia have been reported, especially in studies involving children with epilepsy who were also taking drugs like clobazam or valproate Madeo2023Chesney2020Chen2019+1 MORE. CBD can interact with other medications by affecting liver enzymes (such as CYP3A4 and CYP2C19) and drug transporters, which may increase the risk of drug-drug interactions and adverse effects Madeo2023Iffland2017Bergamaschi2011+3 MORE. Monitoring for these interactions is especially important in patients with complex medical regimens.
Tolerability, Dosage, and Long-Term Use
Clinical trials and reviews indicate that even high doses of CBD (up to 1,500 mg/day) are generally well tolerated in humans, with no significant changes in physiological parameters like heart rate, blood pressure, or body temperature Iffland2017Larsen2020Bergamaschi2011. However, there is still a need for more long-term studies to fully understand the chronic safety of CBD, especially outside of epilepsy treatment and in over-the-counter products, which may have variable quality and unknown bioavailability Madeo2023Iffland2017Larsen2020+4 MORE.
Cognitive Safety of CBD
Research shows that CBD does not impair cognitive function in healthy humans, and may even have beneficial effects on cognition in certain populations, such as heavy cannabis users. No negative effects on cognitive processing have been found in clinical trials involving humans without neuropsychiatric disorders .
Regulatory and Safety Considerations
While pharmaceutical-grade CBD (such as Epidiolex/Epidyolex) has undergone rigorous safety testing and is approved for specific seizure disorders, the safety of unregulated, over-the-counter CBD products remains uncertain due to inconsistent quality and lack of standardization Britch2020Wisotzki2024. Regulatory agencies have set conservative guidance values for daily intake (e.g., 10–15 mg/day) based on available human and animal data, mainly due to concerns about liver toxicity and potential reproductive effects .
Conclusion
Overall, CBD is considered safe and well tolerated in humans at therapeutic doses, with most side effects being mild and transient. Serious adverse events are uncommon but can occur, particularly when CBD is combined with other medications. Drug interactions and liver function should be monitored, especially in medically complex patients. More research is needed to clarify the long-term safety of CBD, its effects in broader populations, and the safety of non-pharmaceutical CBD products.
Sources and full results
Most relevant research papers on this topic