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CBD and the liver

CBD can raise liver enzymes on blood tests. What trials found at each dose, who is most at risk, and how prescribers monitor for it.

Facts checked 13 November 20267 min readHow we research

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 it 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 are liver enzymes?

ALT and AST are enzymes that sit inside liver cells. When liver cells are irritated or damaged, these enzymes leak into the blood. Doctors compare the result with the “upper limit of normal” (ULN). The CBD trials reported how many people rose above 3 times the ULN.1

A raised enzyme level is not the same as liver damage. But a rise above 3 times the ULN together with raised bilirubin (a yellow pigment the liver clears) is treated as an important predictor of severe liver injury.1

What did the trials find?

Study Who CBD dose What happened
Epidyolex epilepsy trials1 Children and adults with severe epilepsy, on other anti-seizure medicines 10 to 25 mg/kg/day (about 700 to 1,750 mg a day for a 70 kg adult) ALT above 3 times ULN in 13% (Dravet and Lennox-Gastaut syndromes) and 12% (tuberous sclerosis), against 1% on placebo
United States FDA trial, 202523 201 healthy adults aged 18 to 55 5 mg/kg/day (about 350 to 400 mg a day) for 28 days 8 people on CBD (5.6%) had enzymes above 3 times ULN; none on placebo
Watkins and others, 20214 16 healthy adults 1,500 mg a day for about 3.5 weeks 7 (44%) had ALT above normal; 5 (31%) exceeded 5 times ULN
Knee osteoarthritis trial, 20235 86 adults also taking paracetamol 3 g a day 600 mg a day for 8 weeks Liver enzyme rises in 15 people on CBD and 5 on placebo
Observational study, 20236 839 adults using retail CBD products in the United States Average 50 mg a day (range 2.5 to 390 mg) for at least 30 days Raised ALT in 9.1%, similar to the 8.9% in the general adult population

Prescription doses in epilepsy

In the controlled epilepsy trials, fewer than 1% of people on CBD had enzyme levels above 20 times the ULN, and some were admitted to hospital with raised enzymes.1 Rises typically appeared in the first two months, although some were seen up to 18 months after starting, mostly in people taking valproate.1

About two-thirds of cases resolved after CBD was stopped, or after CBD or valproate was reduced. About one-third resolved while CBD continued at the same dose.1

Since the medicine reached the market, cases of other patterns of liver injury (called cholestatic and mixed) have been reported, along with raised ammonia levels in some people who also had enzyme rises.1

Healthy adults on moderate doses

The FDA trial matters because it removed the usual explanations. The participants were healthy adults, not people with epilepsy on several medicines, and were randomly assigned to pharmaceutical-grade CBD or placebo. After 28 days, 8 people on CBD (5.6%) had enzymes above 3 times the ULN and 7 (4.9%) met the trial’s criteria for potential drug-induced liver injury. Nobody on placebo did. None had liver symptoms, and enzymes returned to normal within one to two weeks of stopping.23

Two limits apply. The trial lasted only four weeks, and our figures come from the journal’s press release and news coverage, not the full paper.23 The dose, around 350 to 400 mg a day, is above the 150 mg a day ceiling Australia set for pharmacist-only CBD.7

In the smaller study at 1,500 mg a day, all enzyme rises began within two to four weeks. Six of the 16 participants stopped early. Two had fever and some had nausea, vomiting or abdominal discomfort alongside the rises.4

Lower doses

The only sizeable study of low doses was observational. It followed 839 adults taking their own retail CBD products, at an average of about 50 mg a day. The proportion with raised ALT (9.1%) matched the general United States adult population (8.9%), and there was no link between dose and liver results.6

This is weak reassurance. The study had no placebo group, participants chose to take part, and it was funded by 12 CBD companies.6 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. In the epilepsy trials, ALT above 3 times the ULN occurred in 21% of people taking CBD with valproate, 30% of those taking CBD with valproate and clobazam, 4% with clobazam only, and 3% with neither.1 This is not caused by a change in valproate blood levels, and the mechanism is unknown.8 See CBD drug interactions.

People on higher doses. ALT above 3 times the ULN was reported in 17% of people on 20 mg per kg a day and 1% on 10 mg per kg a day.1

People whose enzymes are already raised. At 20 mg per kg a day, 30% of those who started with ALT above normal went on to exceed 3 times the ULN, against 12% of those who started in the normal range.1

People with existing liver disease. After a single 200 mg dose, people with moderate or severe liver impairment had 2.5 to 5.2 times the CBD blood levels of people with healthy livers. Mild impairment made no difference.1 The prescribing information calls for lower starting doses and slower increases in moderate or severe impairment.1 The Australian product information says people with severe impairment should be treated with particular caution.8

For other medicines that can affect the liver, the prescribing information says there are not enough data to judge the combined risk.1 Alcohol is covered in CBD and alcohol.

How do prescribers monitor the liver?

For prescription CBD in epilepsy, the prescribing information sets out a schedule:1

  1. Blood tests for ALT, AST and bilirubin before starting.
  2. Repeat tests at 1 month, 3 months and 6 months, then periodically.
  3. Extra tests within a month of a dose change, or of adding another medicine that affects the liver.
  4. More frequent tests for people taking valproate or with raised enzymes at the start.

The same document tells prescribers when to pause or end treatment, based on how high the enzymes go and whether bilirubin rises as well.1 The TGA’s general guidance on medicinal cannabis also asks doctors to assess liver function when deciding whether to continue treatment.9

How this schedule applies to someone on a much lower dose is a clinical judgement. It is reasonable to ask your prescriber whether you need a baseline liver test and when it should be repeated.

What other regulators have concluded

In October 2023 the United Kingdom’s Food Standards Agency cut its advised limit for CBD in food supplements to 10 mg a day for a healthy adult, down from 70 mg. It named effects on the liver and sleepiness as the main concerns with higher long-term intake.10

The TGA’s assessment of Epidyolex identified higher dose, use with clobazam or valproate, and abnormal liver tests at the start as risk factors for liver abnormalities.11

Signs to act on

Most enzyme rises cause no symptoms. The prescribing information lists these as signs that need prompt blood tests: unexplained nausea, vomiting, pain in the upper right of the abdomen, fatigue, loss of appetite, jaundice (yellow skin or eyes) and dark urine.1

If you notice any of them, contact your doctor promptly. Decisions about pausing or changing CBD belong with your prescriber. For other effects, see CBD side effects.

Footnotes

  1. 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 ↩9 ↩10 ↩11 ↩12 ↩13 ↩14 ↩15 ↩16 ↩17 ↩18

  2. 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 ↩4

  3. HealthDay. Increased liver enzyme levels seen with use of cannabidiol in adults, 2025 (news report of the same trial). https://www.healthday.com/healthpro-news/liver-health/increased-liver-enzyme-levels-seen-with-use-of-cannabidiol-in-adults ↩ ↩2 ↩3

  4. 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/ ↩ ↩2

  5. 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/ ↩

  6. 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/ ↩ ↩2 ↩3

  7. Therapeutic Goods Administration. Over-the-counter access to low dose cannabidiol (final scheduling decision), 15 December 2020. https://tga.gov.au/node/284859 ↩

  8. Therapeutic Goods Administration. Epidyolex (cannabidiol) Australian Product Information, version attached to the AusPAR, January 2021 (may be superseded). https://www.tga.gov.au/sites/default/files/auspar-cannabidiol-210115-pi.pdf ↩ ↩2

  9. Therapeutic Goods Administration. Guidance for the use of medicinal cannabis in Australia: patient information, version 1, December 2017. https://www.tga.gov.au/sites/default/files/guidance-use-medicinal-cannabis-australia-patient-information.pdf ↩

  10. UK Food Standards Agency and Food Standards Scotland. Provisional cannabidiol (CBD) acceptable daily intake: lay summary, October 2023. https://www.gov.uk/government/publications/provisional-cannabidiol-cbd-acceptable-daily-intake-adi/lay-summary ↩

  11. Therapeutic Goods Administration. Australian Public Assessment Report for cannabidiol (Epidyolex), January 2021. https://www.tga.gov.au/sites/default/files/auspar-cannabidiol-210115.pdf ↩

Common questions

Is CBD bad for your liver?

CBD can raise liver enzymes on blood tests, and the higher the dose the more likely this is. In most trial participants the rise caused no symptoms and reversed when CBD was stopped or reduced. Serious liver injury has been reported rarely with prescription CBD, which is why prescribers order blood tests.

Does low-dose CBD affect the liver?

It is not well studied. Controlled trials showing liver enzyme rises used about 350 mg a day or more. An industry-funded observational study of people taking an average of about 50 mg a day found no more abnormal liver tests than in the general population, but it had no placebo group.

Is CBD safe if I already have liver disease?

This needs a prescriber's judgement. People with moderate or severe liver impairment had 2.5 to 5.2 times the usual CBD blood levels in one study, and the prescribing information calls for lower doses and slower increases. Most trials excluded people with liver disease, so safety data are limited.

What are the warning signs of a liver problem?

Unexplained nausea or vomiting, pain in the upper right of the abdomen, unusual tiredness, loss of appetite, yellowing of the skin or eyes, and dark urine. Most enzyme rises cause no symptoms at all and are found only on blood tests. Contact a doctor promptly if any of these signs appear.

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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