After regular oral use, CBD leaves the body slowly. Its half-life is about 2 to 5 days, and it can be detected in blood for weeks after the last dose.12 Shorter half-lives have been measured for some other routes. Standard drug tests do not look for CBD at all. They look for THC.
What is CBD’s half-life?
Half-life is the time it takes for the amount of a substance in the blood to fall by half. It varies with how CBD is taken and for how long.
| Route and pattern of use | Half-life | Source |
|---|---|---|
| Oral solution, twice a day for 7 days, healthy adults | 56 to 61 hours | US prescribing information for the registered CBD medicine1 |
| Long-term oral dosing | 2 to 5 days | Systematic review of human studies2 |
| Smoked | 31 hours | Same review2 |
| Injected into a vein (research only) | 24 hours | Same review2 |
| Mouth spray | 1.4 to 10.9 hours | Same review2 |
The range is wide. One reason is that CBD dissolves in fat and accumulates in the body with repeated dosing.3 For someone taking an oral product every day, the longer figures are the relevant ones.
How long until CBD is gone?
There is no single figure, but the half-life gives a rough guide. With a half-life of about 2.5 days, the blood level halves every 2.5 days. After 10 days about one-sixteenth remains, and it keeps halving from there.
Direct measurements agree that it lingers. In an Australian study of 17 adults given single oral doses of 15, 300 or 1,500 mg, CBD was still detectable in plasma more than 4 weeks after the 1,500 mg dose.3
“Detectable” is not the same as “active”. A laboratory can find very small traces that have no known effect.
What affects how long CBD stays?
- Dose. The 4-week finding above came after the highest dose tested, 1,500 mg.3
- How long you have taken it. Repeated dosing gives a longer half-life than a single dose.12
- Route. See the table above.2
- Food. A high-fat meal raises total CBD exposure about 4-fold compared with an empty stomach, so more is absorbed to begin with.1 See taking CBD with food.
- Liver function. CBD is broken down in the liver, mainly by two enzymes called CYP2C19 and CYP3A4. The US prescribing information sets lower doses for people with moderate or severe liver impairment.1
- Other medicines. Strong enzyme-inducing medicines such as rifampicin lowered CBD exposure by 32%.1 See CBD drug interactions.
How does CBD leave the body?
More than 94% of the CBD in blood is bound to proteins. The liver converts it to breakdown products, and these leave the body mainly in faeces.1
Will CBD show up on a drug test?
The urine drug tests used in the research below screen for a THC breakdown product, not for CBD. So the question is really whether the product contains THC.
| What was taken | Urine test result |
|---|---|
| Pure CBD, 100 mg, swallowed or vaporised | 1 of 218 samples screened positive at the lowest cut-off. None was confirmed positive4 |
| CBD-dominant cannabis containing 0.39% THC (3.7 mg THC), vaporised | 2 of 6 participants had confirmed positive tests4 |
| Full-spectrum high-CBD extract (0.02% THC), daily for 4 weeks, 14 patients | The authors concluded users “may have positive test results” for the THC metabolite5 |
| Broad-spectrum product for 2 weeks | No THC or metabolites detected in urine6 |
A systematic review found that positive tests after legal CBD or hemp oil products are rare, but they do happen, mainly because of THC in the product.7 A 2025 study found that standard tests cannot reliably tell illicit cannabis use from the use of legal hemp products.8
Mislabelling makes this harder to manage. In a US study of 84 CBD products bought online, only 26 were accurately labelled, and some contained THC.9 Products tested by the TGA under Australia’s prescription pathway were mostly close to their labels.10
For roadside and workplace testing rules, see CBD and drug tests, CBD and driving and CBD at work.
Does CBD turn into THC in the body?
This claim comes from test-tube work. CBD does convert to THC in acid in the laboratory. The World Health Organization concluded: “There is little to no evidence that this conversion occurs in vivo after oral administration of CBD.”11 (“In vivo” means in a living body.) A human study reported that conversion of oral CBD to THC “seems not to occur in humans”.12 A 2020 review found the laboratory literature contradictory, but concluded that most studies suggest CBD is not converted to THC in the body.13
How long do CBD’s effects on the body last after stopping?
Some findings help here.
- Liver enzymes. In a US Food and Drug Administration study of healthy adults taking about 350 to 400 mg a day, raised liver enzymes returned to normal within 1 to 2 weeks of stopping.14
- Withdrawal. Adults who took 1,500 mg a day for 28 days showed no signs or symptoms of withdrawal over a 6-week assessment period.1
- Interactions. CBD changes the blood levels of some other medicines.1 Because CBD clears slowly, ask your prescriber or pharmacist how long that might matter after your last dose. For warfarin, reviewers advise monitoring when starting, stopping or changing a CBD dose.15
People taking prescription CBD for epilepsy should not stop suddenly, because of the risk of more seizures.1 See stopping CBD.
What about pregnancy and breastfeeding?
There are no data on whether CBD passes into human breast milk, and no adequate human data on use in pregnancy.1 Australian guidance says medicinal cannabis is not appropriate for women who are pregnant, planning a pregnancy or breastfeeding.16 How long CBD stays in the body after stopping matters here, so raise it with your doctor early. See CBD in pregnancy and breastfeeding.
Footnotes
-
US National Library of Medicine, DailyMed. Epidiolex (cannabidiol) oral solution: prescribing information, revised 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
-
Millar SA, et al. A systematic review on the pharmacokinetics of cannabidiol in humans, 2018. https://pubmed.ncbi.nlm.nih.gov/30534073/ ↩ ↩2 ↩3 ↩4 ↩5 ↩6 ↩7
-
McCartney D, et al. Effects of cannabidiol on simulated driving and cognitive performance: a dose-ranging randomised controlled trial. Journal of Psychopharmacology, 2022. https://pubmed.ncbi.nlm.nih.gov/35637624/ ↩ ↩2 ↩3
-
Study of urinary drug test results after oral and vaporised cannabidiol and vaporised CBD-dominant cannabis (PubMed record). https://pubmed.ncbi.nlm.nih.gov/31682266/ ↩ ↩2
-
Dahlgren MK, et al. Urinary tetrahydrocannabinol after 4 weeks of a full-spectrum, high-cannabidiol treatment. JAMA Psychiatry, 2021. https://pubmed.ncbi.nlm.nih.gov/33146684/ ↩
-
Study of urine testing after two weeks of a broad-spectrum cannabidiol product (PubMed record). https://pubmed.ncbi.nlm.nih.gov/39509209/ ↩
-
Systematic review of positive drug tests after use of cannabidiol and hemp oil products. https://pmc.ncbi.nlm.nih.gov/articles/PMC13275792 ↩
-
Study of drug testing after low-dose THC from legal hemp products, 2025 (PubMed record). https://pubmed.ncbi.nlm.nih.gov/40704705/ ↩
-
Bonn-Miller MO, et al. Labeling accuracy of cannabidiol extracts sold online. JAMA, 2017. https://jamanetwork.com/journals/jama/fullarticle/2661569 ↩
-
Therapeutic Goods Administration. Testing of medicinal cannabis products being supplied through SAS in Australia. https://www.tga.gov.au/resources/publication/tga-laboratory-testing-reports/testing-medicinal-cannabis-products-being-supplied-sas-australia ↩
-
World Health Organization, Expert Committee on Drug Dependence. Cannabidiol (CBD) critical review report, 2018. https://cdn.who.int/media/docs/default-source/controlled-substances/whocbdreportmay2018-2.pdf ↩
-
A conversion of oral cannabidiol to delta9-tetrahydrocannabinol seems not to occur in humans (journal article). https://pubmed.ncbi.nlm.nih.gov/28861507/ ↩
-
Review of whether cannabidiol converts to THC in the body, 2020 (PubMed record). https://pubmed.ncbi.nlm.nih.gov/32503116/ ↩
-
EurekAlert news release on Florian J, et al., JAMA Internal Medicine, 2025 (cannabidiol and liver enzyme elevations in healthy adults). https://www.eurekalert.org/news-releases/1089832 ↩
-
Systematic review of drug interactions with cannabidiol and other cannabinoids. https://pmc.ncbi.nlm.nih.gov/articles/PMC11167383/ ↩
-
Therapeutic Goods Administration. Guidance for the use of medicinal cannabis in Australia: patient information. https://www.tga.gov.au/sites/default/files/guidance-use-medicinal-cannabis-australia-patient-information.pdf ↩
Common questions
How long does CBD stay in your blood?
After a week of twice-daily oral dosing in healthy volunteers, CBD's half-life was 56 to 61 hours, so levels halve roughly every 2.5 days. In an Australian study, CBD was still detectable in blood more than 4 weeks after a single 1,500 mg dose.
Will CBD show up on a drug test?
The drug tests studied look for THC and its breakdown products, not CBD. In one study of pure CBD at 100 mg, only 1 of 218 urine samples screened positive at the lowest cut-off and none was confirmed. Products that contain any THC, including full-spectrum oils, can produce a positive result.
Does CBD build up in the body?
Yes. CBD is fat-soluble and is cleared slowly, so regular dosing leads to higher and longer-lasting levels than a single dose. Reviews report a half-life of 2 to 5 days after long-term oral use.
Does CBD turn into THC in the body?
The evidence says no. CBD can convert to THC in acid in a test tube, but the World Health Organization found little to no evidence that this happens in people after oral CBD, and a human study did not find it.
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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