A randomised, placebo-controlled trial of 300 mg a day for 14 days in people with mild to moderate COVID-19 found CBD did not change the course of the illness.
How we grade evidenceCBD does not treat COVID-19. A randomised, placebo-controlled trial found that 300 mg of CBD a day for 14 days made no difference to the course of mild to moderate illness. There is no human evidence that it prevents infection either.
What the research shows
The CANDIDATE trial
The fair test was a trial called CANDIDATE, led by Crippa and colleagues in Brazil. It was randomised and double-blind, meaning neither the participants nor the researchers knew who received CBD and who received placebo. It ran at two sites between July and October 2020.1
- Who. People with mild to moderate COVID-19. Of 321 people assessed, 105 were randomised. The main analysis included 91 people: 49 on CBD and 42 on placebo.1
- What. 300 mg of CBD a day, or placebo, for 14 days, added to standard care.12
- Result. In the authors’ words, CBD “failed to alter the clinical evolution of COVID-19”.13
- Safety. Side effects were mostly mild and short-lived, with no significant difference from placebo.1
That is a clear negative result from a controlled trial, which is why this page carries the grade “trials show no benefit”. It is one trial of one dose, in people who were not severely ill. It does not tell us about other doses or about people in hospital.
Why the claim spread
Early in the pandemic, laboratory reports and theories about inflammation led to claims that CBD could prevent or treat COVID-19. Results in cells are the weakest kind of evidence. Our page on how we grade evidence explains why most of them do not hold up in people.
Sellers moved faster than the science. The US Food and Drug Administration (FDA) sent warning letters to companies making COVID-19 claims for their products. Of 38 companies warned in March and April 2020, 8 (21%) sold CBD.4
Long COVID
The research reviewed for this page did not include any completed trial of CBD for long COVID. There is no reliable evidence either way.
What doses were tested
The trial used 300 mg a day for 14 days.1 That is double the 150 mg a day limit for pharmacist-only (Schedule 3) CBD in Australia.5 No lower or higher dose was tested in this trial.
What Australian medical bodies say
No Australian medical body recommends CBD for COVID-19.
- The TGA says medicinal cannabis should be considered only when registered medicines have been tried and have failed.6
- RACGP (the GPs’ college) calls the evidence for medicinal cannabis “limited and inconclusive” and does not recommend or encourage it.7
- As of November 2026, only two cannabis medicines are registered in Australia, and neither is for any infection.8
Advertising prescription medicines to the public is not allowed in Australia, and CBD is a prescription medicine. See why Australian clinics cannot advertise CBD.
Risks to know about
- False reassurance. The main risk is relying on CBD in place of vaccination, testing or proven treatment.
- Interactions. CBD blocks several liver enzymes that process other medicines, and is itself broken down by two of them (CYP2C19 and CYP3A4).9 Other medicines that act on those enzymes can therefore affect CBD levels, and CBD can affect theirs. If you are prescribed a COVID-19 antiviral, tell the prescriber and pharmacist about everything else you take. See CBD drug interactions.
- Side effects. Sleepiness, diarrhoea and reduced appetite are the commonly reported side effects of CBD.9 See CBD side effects.
If you are considering it
- For COVID-19 itself, follow current Australian health advice and talk to your GP, especially if you are at higher risk of severe illness.
- If you already take prescribed CBD for another reason and catch COVID-19, tell whoever treats you so that any new medicine can be checked for interactions.
- Treat any product marketed for COVID-19 or “immune support” with suspicion. See CBD myths and misleading claims.
Footnotes
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Crippa JAS et al. Cannabidiol for COVID-19 patients with mild to moderate symptoms (CANDIDATE study): a randomized, double-blind, placebo-controlled clinical trial. Cannabis and Cannabinoid Research, 2022. https://pmc.ncbi.nlm.nih.gov/articles/PMC9587798 ↩ ↩2 ↩3 ↩4 ↩5 ↩6
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ClinicalTrials.gov. Cannabidiol for COVID-19 patients with mild to moderate symptoms, NCT04467918. https://clinicaltrials.gov/study/NCT04467918 ↩
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Letter discussing the CANDIDATE trial. https://pmc.ncbi.nlm.nih.gov/articles/PMC9070739/ ↩
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Analysis of FDA warning letters for unproven COVID-19 claims, March to April 2020. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7370674/ ↩
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Therapeutic Goods Administration. Final decision on the scheduling of low-dose cannabidiol, 2020. https://tga.gov.au/node/284859 ↩
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Therapeutic Goods Administration. Guidance for the use of medicinal cannabis in Australia: overview. https://www.tga.gov.au/resources/resource/guidance/guidance-use-medicinal-cannabis-australia-overview ↩
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Royal Australian College of General Practitioners. Medical cannabis position statement (2019 update). https://www.racgp.org.au/advocacy/position-statements/view-all-position-statements/clinical-and-practice-management/medical-cannabis ↩
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NPS MedicineWise. Medicinal cannabis: what you need to know. https://www.nps.org.au/professionals/medicinal-cannabis-what-you-need-to-know ↩
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Epidiolex (cannabidiol) US prescribing information, DailyMed, revised 2026. https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=8bf27097-4870-43fb-94f0-f3d0871d1eec ↩ ↩2
Common questions
Does CBD treat or prevent COVID-19?
No. A randomised trial in Brazil gave 300 mg of CBD a day or placebo for 14 days to people with mild to moderate COVID-19, and CBD made no difference to how the illness progressed. No human trial shows that CBD prevents infection.
I read that CBD blocks the virus in the lab. Is that true?
Laboratory findings like that are a starting point for research, not proof of an effect in people. When CBD was tested in people with COVID-19 in a placebo-controlled trial, it did not help. Most treatments that look promising in cells fail in human trials.
Does CBD help long COVID?
The research reviewed for this page did not include any completed trial of CBD for long COVID. Without a controlled trial, there is no reliable evidence either way.
Is it safe to take CBD with COVID-19 antiviral medicines?
Ask your doctor or pharmacist before combining them. CBD affects several liver enzymes that process other medicines and is itself broken down by them, so interactions are possible. No study of CBD with COVID-19 antivirals was found in our research.
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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