Medical Cannabis Did Not Cause Liver Enzyme Elevations in Cancer Patients | Research

The takeaway

Across two randomized controlled trials involving 287 cancer patients, neither CBD alone nor THC/CBD combination caused clinically meaningful liver enzyme elevations over 28 days at doses up to 600 mg CBD per day.

Oncologists, palliative care physicians, cancer patients considering medicinal cannabis, and drug safety researchers.

What the researchers found

No patients in the cannabis groups exceeded predefined safety thresholds (3x upper limit of normal for ALT or AST, or 5x for those with liver metastases). No clinically meaningful differences in liver enzyme levels were observed between CBD-only and THC/CBD combination products or compared with placebo.

Why it matters

Liver safety is a known concern with pharmaceutical CBD (Epidiolex carries a liver enzyme warning). This RCT-derived safety data in a vulnerable cancer population provides reassurance that medicinal cannabis at moderate doses does not appear to cause hepatotoxicity over one month.

The numbers in context

287 patients across two trials. Maximum dose: 600 mg CBD/day. Zero patients exceeded 3x ULN for ALT or AST (or 5x ULN with liver metastases). Measurements at baseline, day 14, and day 28.

How the study worked

Substudy of two multicentre, randomized, placebo-controlled trials (MedCan1: CBD alone; MedCan2: THC/CBD) in 287 patients with advanced cancer. Liver enzymes (ALT, AST) measured at baseline, day 14, and day 28 with escalating doses up to 600 mg CBD/day.

What this study cannot tell us

Only 28 days of follow-up; longer-term effects unknown. Maximum dose of 600 mg CBD/day is lower than some clinical protocols. Patients with severely impaired liver function may have been excluded from the original trials. Substudy analysis was not the primary endpoint of either trial.

How to read the evidence

RCT-derived safety data with placebo comparison and predefined thresholds, though short duration and substudy design limit the strength of conclusions.

When this study was published

Published 2025.

The bigger picture

Cancer patients often have compromised liver function from chemotherapy, metastases, or both. Demonstrating that medicinal cannabis does not add to hepatic burden at therapeutic doses strengthens the case for its use in palliative care, where quality of life is the primary concern.

Questions still open

Whether longer-duration cannabis use at these doses would eventually affect liver enzymes
Whether higher CBD doses (above 600 mg/day) would show a different safety profile in cancer patients

Common questions

Does this mean cannabis is safe for the liver?

Over 28 days at doses up to 600 mg CBD/day in cancer patients, no liver enzyme problems were detected. However, this does not rule out effects at higher doses, with longer use, or in people with pre-existing liver disease.

Why is liver safety a concern with CBD?

The FDA-approved CBD medication Epidiolex carries a warning about potential liver injury, based on clinical trial data showing elevated liver enzymes in some patients, particularly at high doses or when combined with certain anti-seizure medications.

Read the original research

Liver enzyme effects of medicinal cannabis in advanced cancer: a substudy of two randomised trials.

BMJ supportive & palliative care

View on PubMed ↗Publisher’s paper ↗

Citation

Scarborough, Luke; Hardy, Janet; Gurgenci, Taylan; Huggett, Georgie; Pelecanos, Anita; Webb, Lachlan; Greer, Ristan; Good, Phillip. (2025). Liver enzyme effects of medicinal cannabis in advanced cancer: a substudy of two randomised trials.. BMJ supportive & palliative care. https://doi.org/10.1136/spcare-2025-005837