How Long Does CBD Stay in Your System? Half-Life by Route
CBD's reported half-life runs from 1.4 hours to 5 days by route. The figures, the UK product each fits, and what a drug test actually looks for.
By Staff, CBD Wire
How long CBD stays in your system depends on how you take it. A 2018 systematic review reported a half-life of 1.4 to 10.9 hours after a spray, 2 to 5 days after repeated daily oral dosing, 24 hours intravenously and 31 hours after smoking. The urine drug screens in a US study looked for a THC metabolite, not CBD.
This is an evergreen explainer. The figures come from one review of the published human data, and they will not change until better data does. This desk read the review’s abstract, a urine-testing study and the Food Standards Agency’s CBD guidance on 1 November 2026.
How long does CBD stay in your system, by route?
The source is Millar and colleagues’ systematic review, published in Frontiers in Pharmacology in November 2018 by researchers at the University of Nottingham, with one author at Artelo Biosciences. They searched PubMed and EMBASE and, of 792 articles retrieved, found 24 that reported pharmacokinetic figures in humans.
The table matches each route in the review to the closest product a UK buyer actually sees. The last column is this desk’s arithmetic, not a figure from the review: after one half-life half the CBD remains, and after five about 3% does (0.5 to the fifth power is 0.031).
| Route in the review | Reported half-life | Closest UK product shape | Five half-lives (our arithmetic) |
|---|---|---|---|
| Oromucosal spray | 1.4 to 10.9 hours | Oil drops held under the tongue | About 7 to 55 hours |
| Chronic oral dosing | 2 to 5 days | Daily oil, gummies or drinks taken for weeks | About 10 to 25 days |
| Intravenous | 24 hours | None sold to consumers | About 5 days |
| Smoking | 31 hours | Smoked CBD flower | About 6.5 days |
Three cautions sit on that table. The spray figures are for an oromucosal spray, not retail oils, so oil drops are the closest shape, not a measured match. “Chronic oral” means repeated daily dosing, not a single gummy. And the smoked row is about smoking, not vaping.
What about vapes?
The review gives no half-life for vaping, and the 31-hour figure should not be borrowed for it. The nearest published data this desk read is the urine study below, which reports that urinary CBD peaked within an hour of vaping 100mg, against about five hours after the same oral dose. That is timing, not clearance. The site’s piece on what goes in a CBD vape covers the product side.
On flower, this post says nothing new about whether smoking it is lawful; the site’s Home Office reading on CBD flower does.
How reliable are these half-life figures?
Less than the tidy table suggests, and the review says so itself. Its conclusion highlights “the paucity in data and some discrepancy” in CBD pharmacokinetics. It found that bioavailability was reported only for smoking, at 31%, that peak levels arrive between 0 and 4 hours, and that peak levels are higher when CBD is taken with food or in a lipid formulation.
The review is from 2018. This desk did not check whether a newer review exists, so it is not described here as the latest word.
Does CBD show up on a drug test?
The urine screens in the study below were not looking for CBD. They looked for THC-COOH, the metabolite of THC. The study this desk read is a Johns Hopkins study in the Journal of Analytical Toxicology, which gave six healthy adults 100mg of oral CBD, 100mg of vaporised CBD, vaporised CBD-dominant cannabis containing 3.7mg of THC, and a placebo.
After pure CBD, 1 of 218 urine samples screened positive at the most sensitive cutoff and none passed the confirmation test. After the cannabis vapour with THC, four samples confirmed positive. The authors conclude that acute pure CBD will not produce a positive under US federal workplace guidelines, but CBD products that also contain THC may. Those are US cutoffs from a six-person study; a UK employer’s laboratory may use different ones. The site’s drug-test post on Trip covers the UK tests themselves.
What does the FSA advise on daily intake?
The FSA’s CBD guidance, which applies to England and Wales and was first published on 13 February 2020 and last updated on 28 August 2026, cites a provisional acceptable daily intake of 10mg of CBD a day, for CBD of at least 98% purity, and a safe upper limit of 70 micrograms a day of delta-9-THC. It recommends that businesses reformulate products in line with those levels, and frames them as advised limits.
FAQ
How long does CBD stay in your urine?
In the Johns Hopkins study, urinary CBD peaked about 5 hours after a 100mg oral dose and within an hour after vaping 100mg, with urine collected for five days. The abstract this desk read gives peak timing, not a clearance time, so no urine window is printed here. What a urine drug screen looks for is a THC metabolite, not CBD.
Does full spectrum CBD show up on a drug test more than isolate?
The study that settles the mechanism did not test labels; it tested THC content. Pure CBD produced no confirmed positives, while CBD-dominant cannabis vapour carrying 3.7mg of THC produced four. A full-spectrum product keeps other cannabinoids by design, so the question to ask of any product is how much THC its batch lab report shows.
Is CBD detectable in a hair follicle test?
Neither paper this desk read studied hair. The systematic review covers blood pharmacokinetics and the urine study covers five days of urine, so no hair figure is printed here. On the evidence this desk read for urine, it is the THC in a CBD product, not the CBD, that turns a screen positive.
How long do the effects of CBD last?
This desk read no source that measures how long effects last, and CBD Wire does not describe products by what they do to a body. The review reports that peak blood levels are reached between 0 and 4 hours after dosing, and sooner after smoking or inhalation than after oral routes. That is a timing figure, not an effect.
The short version
Half-life tells you how fast CBD leaves, and the honest range runs from hours to days by route. The drug-test risk sits with THC, so read the batch lab report before you read the price. The FSA classes CBD extracts and isolates as novel foods, which require authorisation before sale in the UK. The FSA does not recommend CBD for people who are pregnant, breastfeeding, trying to conceive or taking any medication, unless under medical direction. If you face workplace testing, ask the testing provider what it screens for.
