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CBD Side Effects & Safety

Evidence:Emerging
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This content is for informational purposes only and does not constitute medical advice. Statements about dietary supplements have not been evaluated by the FDA and are not intended to diagnose, treat, cure, or prevent any disease. Individual results may vary — consult your healthcare provider before starting any supplement. Full disclaimer

Safety Profile

Overall safety rating: Safe with Caution

Potential Side Effects

  • Fatigue and drowsiness (dose-dependent, common)
  • Diarrhea (more common at higher doses)
  • Changes in appetite and weight
  • Dry mouth
  • Liver enzyme elevation at very high doses (Epidiolex studies at 10-20mg/kg/day)
  • Drug-drug interactions via CYP450 enzyme inhibition (see interactions)

Drug & Supplement Interactions

  • CYP3A4 and CYP2C19 substrates — CBD significantly inhibits these enzymes, affecting metabolism of many medications (statins, calcium channel blockers, etc.)
  • Blood thinners (warfarin) — CBD can increase warfarin levels; INR monitoring needed
  • Clobazam and other anti-epileptics — CBD increases clobazam levels; relevant for epilepsy patients
  • Sedative medications — additive sedation effects
  • SSRIs — CBD modulates serotonin; theoretical interaction but generally considered safe at standard doses
  • Grapefruit warning drugs — CBD inhibits similar CYP enzymes as grapefruit juice

Maximum Dose

Do not exceed: 600mg/day has been used in clinical research without serious adverse effects (higher doses used in epilepsy under medical supervision)

Full CBD Guide

References

  1. Case reportShannon S, Lewis N, Lee H, Hughes S (2019). Cannabidiol in anxiety and sleep: a large case series. Permanente Journal. DOI PubMed
  2. RCTLinares IM, Zuardi AW, Pereira LC, et al. (2019). Cannabidiol presents an inverted U-shaped dose-response curve in a simulated public speaking test. Brazilian Journal of Psychiatry. DOI PubMed
  3. RCTZuardi AW, Cosme RA, Graeff FG, Guimarães FS (1993). Effects of ipsapirone and cannabidiol on human experimental anxiety. Journal of Psychopharmacology. DOI PubMed
  4. ReviewBlessing EM, Steenkamp MM, Manzanares J, Marmar CR (2015). Cannabidiol as a potential treatment for anxiety disorders. Neurotherapeutics. DOI PubMed
  5. Meta-analysisHan K, Wang JY, Wang PY, Peng YC (2024). Therapeutic potential of cannabidiol (CBD) in anxiety disorders: A systematic review and meta-analysis.. Psychiatry research. DOI PubMed
  6. Lo LA, Christiansen AL, Strickland JC, Pistawka CA, et al. (2024). Does acute cannabidiol (CBD) use impair performance? A meta-analysis and comparison with placebo and delta-9-tetrahydrocannabinol (THC).. Neuropsychopharmacology : official publication of the American College of Neuropsychopharmacology. DOI PubMed
  7. Freeman TP, Craft S, Wilson J, Stylianou S, et al. (2021). Changes in delta-9-tetrahydrocannabinol (THC) and cannabidiol (CBD) concentrations in cannabis over time: systematic review and meta-analysis.. Addiction (Abingdon, England). DOI PubMed
Show 5 more references
  1. Dos Santos MC, da Silva AMP, da Vitória Santos do Nascimento M, da Silva TMS, et al. (2026). The Influence of CBD and THC on Hepatic Enzymes of the Human Cytochrome P450 Complex Family: A Systematic Literature Review.. European journal of drug metabolism and pharmacokinetics. DOI PubMed
  2. Duan S, Liu M, An Z, Zhong Z, et al. (2026). Unlocking the potential: Cannabidiol (CBD) as a promising anti-tumor agent.. Phytomedicine : international journal of phytotherapy and phytopharmacology. DOI PubMed
  3. Gras M, Bearden D, West J, Nabbout R (2024). Efficacy of anti-seizure medications and alternative therapies (ketogenic diet, CBD, and quinidine) in KCNT1-related epilepsy: A systematic review.. Epilepsia open. DOI PubMed
  4. Aderinto N, Olatunji G, Kokori E, Ajayi YI, et al. (2024). The efficacy and safety of cannabidiol (CBD) in pediatric patients with Dravet Syndrome: a narrative review of clinical trials.. European journal of medical research. DOI PubMed
  5. Hindelang P, Scharinger A, Richling E, Walch SG, et al. (2022). Using the BMD Approach to Derive Acceptable Daily Intakes of Cannabidiol (CBD) and Tetrahydrocannabinol (THC) Relevant to Electronic Cigarette Liquids.. Frontiers in bioscience (Landmark edition). DOI PubMed