Last updated 9 August 2026 · Originally published 4 January 2021
Worries about CBD and the liver took hold in 2019, when a mouse study made headlines suggesting cannabidiol might be toxic to it. Since then the picture has improved considerably, with human trials involving thousands of participants and, in 2025, a randomised study conducted specifically in healthy adults.
The short answer is that CBD can raise liver enzymes. It’s dose-dependent, and it matters a great deal what else you’re taking.
The mouse study, and why it wasn’t the answer
Researchers at the University of Arkansas gave mice a CBD-rich extract and found clear liver toxicity at the highest dose.[1] The coverage was alarming.
The highest mouse dose was 2,460 mg per kilogram. After the usual conversion between species, the researchers treated that as equivalent to 200 mg/kg in humans — about 14,000 mg for a 70 kg adult. Even the lowest dose in the acute experiment corresponded to 20 mg/kg in humans, the upper end of prescription CBD dosing and far beyond ordinary retail use.
The study wasn’t wrong. It established that an extremely high dose of a CBD-rich extract could damage a mouse liver. What it couldn’t tell us was whether the amounts people normally take pose the same risk.
What the human evidence shows
A 2023 systematic review pooled 28 clinical trials covering 1,533 people taking CBD.[2] It provides the broadest estimate we have.
Raised liver enzymes occurred in about 7% of people taking CBD, and about 3% met the review’s criteria for drug-induced liver injury. Both were significantly more common than on placebo.
But the risk wasn’t spread evenly, and two findings matter more than the headline figures.
It was concentrated at high doses. The risk factors were CBD at 1,000 mg or more per day, or 20 mg per kilogram of body weight. And critically: no cases were reported in adults taking under 300 mg a day.
Anti-epileptic drugs made it much worse, valproate in particular. A large share of the liver signal comes from people taking CBD alongside these medications rather than from CBD alone.
No severe cases were reported. Most enzyme elevations eventually resolved — some after CBD was stopped, some after doses were adjusted, and around a quarter while CBD use continued.
What changed in 2025
One finding complicates the reassuring version.
An FDA-funded randomised trial gave healthy adults — no epilepsy, no other medication — 5 mg per kilogram of CBD daily for 28 days. Eight participants, about 5.6%, developed liver enzyme elevations more than three times the upper limit of normal. Nobody on placebo did. Seven met the study’s withdrawal criteria for potential drug-induced liver injury, though that classification doesn’t necessarily mean clinically apparent damage.[3]
One participant reported temporary upper-abdominal discomfort. There were no serious events or clinically significant changes in liver function, and enzyme levels returned to normal within one to two weeks of stopping.
That dose is roughly 350 mg a day for a 70 kg adult: well above a typical gummy, but below where the meta-analysis found most of its cases — and in people taking nothing else. It shows the effect isn’t confined to high-dose epilepsy patients on multiple drugs.
So how worried should you be?
It depends mainly on your dose, what else you take, and your existing liver health.
Low retail doses — the 10 to 50 mg most products deliver — are far below the doses associated with problems in these studies. The 2023 review reported no adult cases below 300 mg a day, and studies using less than 50 mg haven’t reported enzyme elevations above three times the upper limit of normal. But those low-dose studies were relatively small, so the evidence supports a lower risk rather than a guarantee of none.
High doses, whether prescription or self-administered, carry a real and measurable risk. This is one of the strongest arguments against simply escalating your dose until something happens.
If you take anti-epileptic medication, particularly valproate, this is a conversation for your doctor rather than something to work out yourself.
If you already have liver problems, or raised enzymes at baseline, there’s some evidence the risk is higher.
Some perspective
Plenty of ordinary medicines can affect the liver. Paracetamol overdose is a leading cause of acute liver failure in the UK and US, and paracetamol is sold in supermarkets.[4]
That isn’t a reason to dismiss the CBD findings — it’s a reason to treat CBD like a pharmacologically active substance rather than a wellness product that can’t do harm. Prescription CBD carries a liver warning on its label and patients have their liver function monitored before and during treatment. That’s the appropriate level of seriousness, applied at doses where the risk is real.
What to do
Know your actual dose in milligrams per day, not servings.
Tell your doctor you’re taking it, particularly before any blood tests.
Don’t combine high-dose CBD with anti-epileptic medication without medical supervision.
Watch for symptoms — unusual tiredness, nausea, abdominal pain, dark urine or yellowing of the skin or eyes all warrant medical attention.
None of this is medical advice. If you have a liver condition or take medication that affects the liver, speak to a doctor before starting CBD.
For more, see our guide to CBD and drug interactions, our guide to CBD and what the research actually shows, or browse Health Conditions.
References
- Ewing LE, Skinner CM, Quick CM, et al. Hepatotoxicity of a cannabidiol-rich cannabis extract in the mouse model. Molecules. 2019;24(9):1694. doi:10.3390/molecules24091694
- Lo LA, Christiansen A, Eadie L, et al. Cannabidiol-associated hepatotoxicity: a systematic review and meta-analysis. Journal of Internal Medicine. 2023;293(6):724–752. doi:10.1111/joim.13627
- Florian J, Salcedo P, Burkhart K, et al. Cannabidiol and liver enzyme level elevations in healthy adults: a randomized clinical trial. JAMA Internal Medicine. 2025;185(9):1070–1078. doi:10.1001/jamainternmed.2025.2366
- National Institute of Diabetes and Digestive and Kidney Diseases. Acetaminophen. In: LiverTox: Clinical and Research Information on Drug-Induced Liver Injury. NCBI Bookshelf
About this article
Substantially rewritten in August 2026. The original was built around a 2019 mouse study; this update replaces it with human evidence — a meta-analysis of 28 clinical trials and a 2025 randomised trial in healthy adults — and sets out how the risk varies by dose and by what else you take. With earlier reporting by Lydia Kariuki.
