CBD can raise liver enzymes, which is a blood-test signal that the liver is under stress. The effect depends on dose, is usually symptom-free and usually reverses when CBD is stopped or reduced.1 It is clearly documented from about 350 mg a day upward and is much more common in people who also take the anti-seizure medicine valproate.12 Below 150 mg a day there is very little controlled evidence either way.
What did the trials find?
| Study | Who | CBD dose | What happened |
|---|---|---|---|
| Epilepsy trials1 | People with severe epilepsy on other medicines | 10 to 25 mg/kg/day | Enzymes above 3 times the normal limit in 13% (Dravet and Lennox-Gastaut) and 12% (tuberous sclerosis), against 1% on placebo |
| US FDA trial, 20252 | 201 healthy adults | About 350 to 400 mg a day for 28 days | 5.6% on CBD had a significant rise; none on placebo |
| Healthy adults, 20213 | 16 healthy adults | 1,500 mg a day | 44% had ALT above normal; 31% above 5 times the limit |
| Knee osteoarthritis, 20234 | 86 adults also on paracetamol | 600 mg a day for 8 weeks | Rises in 15 on CBD and 5 on placebo |
In the FDA trial nobody had liver symptoms, and enzymes returned to normal within one to two weeks of stopping. The trial lasted only four weeks, and our figures come from the press release, not the full paper.2
What about low doses?
The only sizeable low-dose study was observational: 839 adults taking retail CBD at an average of about 50 mg a day had raised ALT at a rate (9.1%) similar to the general population (8.9%). It had no placebo group and was funded by 12 CBD companies.5 A fair summary is that liver effects at 150 mg a day or less have not been properly tested.
Who is most at risk?
- People taking valproate. Enzyme rises occurred in 21% of people taking CBD with valproate, 30% with valproate and clobazam, and 3% with neither.1
- People on higher doses.1
- People with liver disease. Moderate or severe liver impairment gave 2.5 to 5.2 times the CBD blood levels.1
Alcohol has not been tested for its effect on this risk. See can you drink alcohol while taking CBD?
How is it monitored?
For prescription CBD in epilepsy, liver blood tests are done before starting, at 1, 3 and 6 months, then periodically.1 For lower doses this is a clinical judgement, so ask your prescriber whether you need a baseline test.
What signs should you act on?
Unexplained nausea, vomiting, pain in the upper right of the abdomen, fatigue, loss of appetite, yellow skin or eyes, or dark urine. Contact your doctor promptly.1
Read the full guide: CBD and the liver.
Footnotes
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Jazz Pharmaceuticals. Epidiolex (cannabidiol) oral solution, US prescribing information, DailyMed (accessed November 2026). https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=8bf27097-4870-43fb-94f0-f3d0871d1eec ↩ ↩2 ↩3 ↩4 ↩5 ↩6 ↩7 ↩8
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JAMA Network. News release on Florian J and others, cannabidiol and liver enzyme level elevations in healthy adults, JAMA Internal Medicine, 7 July 2025. https://www.eurekalert.org/news-releases/1089832 ↩ ↩2 ↩3
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Watkins PB, Church RJ, Li J, Knappertz V. Cannabidiol and abnormal liver chemistries in healthy adults: results of a phase I clinical trial. Clinical Pharmacology and Therapeutics, 2021. https://pmc.ncbi.nlm.nih.gov/articles/PMC8246741/ ↩
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Pramhas S and others. Randomised trial of cannabidiol 600 mg a day added to paracetamol for knee osteoarthritis. The Lancet Regional Health Europe, 2023. https://pmc.ncbi.nlm.nih.gov/articles/PMC10682664/ ↩
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Kaufmann R, Aqua K, Lombardo J, Lee M. Observed impact of long-term consumption of oral cannabidiol on liver function in healthy adults. Cannabis and Cannabinoid Research, 2023. https://pmc.ncbi.nlm.nih.gov/articles/PMC9940803/ ↩
This page is general information, not medical or legal advice. Laws and evidence change; we show the date we last checked the facts at the top of every page. Talk to your doctor or pharmacist before starting, stopping or changing any medicine.
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