Liver-Related Considerations for Cannabinoids

CBD (cannabidiol) is sold as an approved prescription medicine and, in many places, as consumer oils and gummies. The liver warning on the prescription label is one of the clearest safety signals for CBD. This page explains what that signal is, what trials in healthy adults found, and what is still unknown. It is education only, not medical advice, and it gives no amounts for personal use. Amounts mentioned below are what a study or label used.

How evidence is labeled here. Approved medicine means a regulator has approved a product for a stated use. Established means consistent findings across good studies. Mixed means findings differ. Insufficient evidence means too little research. Preclinical means cells or animals only.

What the liver warning says

Epidiolex is a purified CBD medicine approved by the US FDA for seizures linked to Lennox-Gastaut syndrome, Dravet syndrome and tuberous sclerosis complex in people aged one year and older. [1] Label: approved medicine. Its prescribing information states it can cause dose-related rises in liver enzymes (ALT and AST) and asks prescribers to check liver blood tests before treatment starts. [1] In controlled trials, ALT above three times the upper limit of normal occurred in about 12% to 13% of treated patients compared with 1% on placebo. [1] The rises typically appeared in the first two months, though some cases appeared up to 18 months later, and the risk was higher with the seizure medicine valproate. [1] About two-thirds of the rises resolved when the medicine was stopped or reduced, and about one-third resolved without a dose change. [1] After the product was on the market, cholestatic or mixed patterns of liver injury were reported. [1] The label also calls for dosage adjustment in moderate or severe liver impairment. [1]

What the FDA says about consumer CBD

The FDA states that CBD can cause liver injury. [2] It says the injury was seen in the Epidiolex review even in patients not taking other liver-affecting drugs, that it was found through blood tests, and that it is concerned the same injury could go undetected when people take CBD without medical monitoring. [2] NCCIH adds that abnormal liver function tests in the Epidiolex studies appeared to be due to CBD itself rather than contaminants. [3]

Trials in healthy adults

In a 2021 phase 1 trial, 16 healthy adults took CBD at 1,500 mg a day (the study amount, not a recommendation) for about 3.5 weeks. [4] Seven (44%) had ALT above the upper limit of normal, and five (31%) went above five times that limit, meeting international criteria for drug-induced liver injury. [4] Rises began within 2 to 4 weeks, and some participants had symptoms consistent with hepatitis or hypersensitivity. [4] The authors found no link with genetics or blood levels, so they could not say who is most at risk. [4]

A 2023 systematic review pooled clinical trials of daily CBD. It reported higher odds of liver enzyme elevation (odds ratio 5.85) and drug-induced liver injury (4.82) than placebo. [5] High amounts (1,000 mg a day or 20 mg/kg a day or more) and use of other antiepileptic medicines were identified as risk factors. [5] The review reported no cases in adults at the lower amounts in its trials (under 300 mg a day) and no cases of severe injury. [5] That is a count of what trials reported, not a safe-amount finding. Label: established that CBD can raise liver enzymes at the amounts studied; mixed on risk at lower amounts, because most trials were short and in specific groups.

A 2024 narrative review concluded that CBD-related liver enzyme rises and injury meet the standard definition of a common adverse drug reaction but are unknown to many clinicians. It advises screening for CBD use in people who present with high liver enzymes. [6]

What this means for consumer products

Consumer products are not standardized the way a prescription is. NCCIH says over-the-counter CBD products may contain more or less CBD than their labels state and may contain contaminants such as THC. [3] A person therefore may not know how much CBD they are taking. See product quality and certificates of analysis and adulterated and mislabeled products.

Existing liver disease

For people who already have liver disease, the sources read give limited direct evidence on CBD. A 2024 review of CBD in liver disease described benefits only in cell and animal models and said the lack of evidence hinders use in clinical practice. [7] Label: preclinical. The prescription label says dosage adjustments are necessary in moderate or severe liver impairment. [1]

For THC and cannabis, a 2018 meta-analysis of three studies (898 people with hepatitis C) found higher, but not statistically significant, odds of advanced liver scarring among people who used cannabis (odds ratio 1.77, with a range of 0.78 to 4.02). [8] Label: insufficient evidence.

Other medicines and alcohol

The Epidiolex label says the risk of enzyme rises increases with valproate and that data are insufficient to assess other liver-affecting drugs. [1] Combining CBD with alcohol or sedating drugs raises the risk of sedation. [2] Broader guidance is in liver safety and supplements and CBD-medication interactions.

Talking with a clinician

Anyone with liver disease, taking medicines that affect the liver, or using CBD regularly can tell their prescriber so liver tests can be considered. Do not stop a prescribed medicine without asking the prescriber.