CBD LoveThe independent Australian guideSearch

How long does CBD take to work?

Swallowed CBD reaches its peak blood level in about 2.5 to 5 hours. Whether and when symptoms change depends on the condition, and trials ran for weeks.

Facts checked 13 November 20267 min readHow we research

Swallowed CBD reaches its highest level in the blood about 2.5 to 5 hours after a dose.1 That is a fact about absorption, not about benefit. Whether symptoms change, and how soon, depends on the condition. For several common uses, controlled trials found no difference from placebo (a dummy treatment) at any time point.

How fast does CBD reach the bloodstream?

It depends on how it is taken.

Route Time to peak blood level Where the figure comes from
Swallowed oral solution About 2.5 to 5 hours Repeated dosing of the registered CBD medicine, from its US prescribing information1
Inhaled (aerosol or vapour) 5 to 10 minutes World Health Organization review2
All routes pooled 0 to 4 hours Systematic review of human studies across routes and doses3

Time to peak blood level is often written as Tmax. A shorter Tmax means faster absorption. It does not mean a stronger or better effect.

Under-the-tongue (sublingual) use is often said to be faster than swallowing. Much of a sublingual dose is swallowed anyway, and reliable human measurements for this route are lacking.4 See bioavailability.

How long before a dose did trials give CBD?

Single-dose studies give a sense of the timing researchers expected.

  • Public-speaking anxiety. People with social anxiety disorder took a single 600 mg dose 1.5 hours before a simulated speech. Anxiety during the speech was lower than with placebo.5
  • Exercise. Nine endurance-trained men took 300 mg by mouth 1.5 hours before a running test. There was no difference in time to exhaustion.6
  • Insomnia. Thirty adults took 150 mg under the tongue 1 hour before bed for 2 weeks. Most sleep outcomes were similar to placebo.7
  • Acute low back pain. One hundred adults in a Melbourne emergency department took a single 400 mg oral dose or placebo. Pain scores 2 hours later were not different (6.2 with CBD, 5.8 with placebo).8

These studies show when researchers looked for an effect. Only the first found one.

How long before symptoms change?

In the trials that did find a difference from placebo, it appeared over days to weeks.

Epilepsy. In pooled data from trials in Lennox-Gastaut syndrome (a severe childhood epilepsy), the seizure benefit separated from placebo within the first 1 to 2 weeks, while the dose was still being raised.9 The main trial in Dravet syndrome, another severe childhood epilepsy, ran for 14 weeks.10

Other conditions. Most trials judged the result after weeks of daily dosing:

Condition Dose Trial length Result
Cannabis use disorder 400 or 800 mg/day 4 weeks Reduced cannabis use11
Schizophrenia 1,000 mg/day added to antipsychotics 6 weeks Modest improvement in some symptoms12
Knee osteoarthritis pain 600 mg/day 8 weeks No difference from placebo13
Treatment-resistant anxiety in young people (no placebo group) Up to 800 mg/day 12 weeks Anxiety scores fell, but a placebo effect could not be ruled out14
Hand osteoarthritis and psoriatic arthritis pain 20 to 30 mg/day 12 weeks No difference from placebo15

For the uses where trials found no benefit, waiting longer is not known to change the answer. The arthritis trial ran for 12 weeks and still found nothing.15 Each condition page gives the details.

Why does it take time to reach the full dose?

Prescription CBD is usually titrated, which means starting low and stepping up. The US prescribing information for CBD oral solution in epilepsy starts at 5 mg per kilogram per day and increases after one week.1 So the first week or more is spent below the intended dose. See starting CBD.

CBD also builds up with repeated dosing. It is fat-soluble and leaves the body slowly, with a half-life (the time for the blood level to halve) of 56 to 61 hours after a week of twice-daily dosing in healthy volunteers.1 In one study of healthy volunteers, blood levels reached a steady state after about 2 days of twice-daily dosing.16 See how long CBD stays in your system.

Does food change how quickly or strongly it works?

Food changes how much CBD is absorbed, by a lot. A high-fat meal raised the peak blood level of the oral solution about 5-fold and total exposure about 4-fold compared with an empty stomach.1 A dose taken with dinner one day and on an empty stomach the next can give very different blood levels. That makes it harder to tell whether a treatment is working. See taking CBD with food.

Will you feel it when it starts working?

Probably not in the way people expect. CBD is not intoxicating. In a study of abuse potential, single doses of 750 to 4,500 mg did not produce the “drug liking” effects seen with THC or a sedative.1 In an Australian study, single oral doses of 15, 300 or 1,500 mg caused no feelings of intoxication.17

What people do notice early is more often a side effect. Sleepiness or sedation affected 32% of people on prescription CBD in epilepsy trials, against 11% on placebo.1 See CBD side effects.

Because there is no clear “it is working” sensation, and because conditions such as pain, anxiety and poor sleep rise and fall on their own, a simple symptom diary, started before the first dose, gives you and your prescriber something firmer than memory to review.

How long do the effects last?

This has not been well measured for symptoms. Two findings give some idea.

  • In 42 abstinent people with heroin use disorder, 400 or 800 mg a day for 3 days reduced craving triggered by drug cues, and the effect lasted up to a week.18
  • In 26 healthy men, a drop in resting blood pressure seen after a first 600 mg dose was lost after 7 days of repeated dosing.19

Neither result tells you how long any effect would last for you.

What if nothing happens?

That is a common outcome in trials, and it is useful information. TGA guidance says treatment with medicinal cannabis should be stopped if benefit has not been demonstrated.20 Raising the dose yourself is not the answer. The TGA’s assessment of the registered CBD medicine identified higher dose as a risk factor for liver abnormalities.21 Talk to your prescriber about a review date before you start, and see stopping CBD and the CBD dosage guide.

Footnotes

  1. 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

  2. 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 ↩

  3. Millar SA, et al. A systematic review on the pharmacokinetics of cannabidiol in humans, 2018. https://pubmed.ncbi.nlm.nih.gov/30534073/ ↩

  4. Review of cannabidiol delivery routes and oromucosal bioavailability estimates (journal article). https://pmc.ncbi.nlm.nih.gov/articles/PMC7558665/ ↩

  5. Bergamaschi MM, et al. Cannabidiol reduces the anxiety induced by simulated public speaking in treatment-naive social phobia patients, 2011. https://pubmed.ncbi.nlm.nih.gov/21307846/ ↩

  6. Sahinovic A, et al. Effects of cannabidiol on exercise physiology and bioenergetics: a randomised controlled pilot trial. Sports Medicine Open, 2022. https://pmc.ncbi.nlm.nih.gov/articles/PMC8891421 ↩

  7. Narayan AJ, et al. Cannabidiol for moderate-severe insomnia: a randomized controlled pilot trial of 150 mg of nightly dosing. Journal of Clinical Sleep Medicine, 2024. https://pubmed.ncbi.nlm.nih.gov/38174873/ ↩

  8. Bebee B, et al. The CANBACK trial of oral cannabidiol for acute low back pain in the emergency department. Medical Journal of Australia, 2021. https://www.mja.com.au/journal/2021/cannabidiol-no-better-placebo-low-back-pain ↩

  9. Long-term cannabidiol treatment in Lennox-Gastaut syndrome: open-label extension results. Epilepsia (copy hosted by University College London). https://discovery.ucl.ac.uk/id/eprint/10126054/1/epi.16878.pdf ↩

  10. Devinsky O, et al. Trial of cannabidiol for drug-resistant seizures in the Dravet syndrome. New England Journal of Medicine, 2017. https://doi.org/10.1056/NEJMoa1611618 ↩

  11. Freeman TP, et al. Cannabidiol for the treatment of cannabis use disorder: a phase 2a, double-blind, placebo-controlled, randomised, adaptive Bayesian trial. Lancet Psychiatry, 2020. https://pmc.ncbi.nlm.nih.gov/articles/PMC7116091/ ↩

  12. Review summarising McGuire et al., 2018 (cannabidiol 1,000 mg/day as add-on therapy in schizophrenia). https://pmc.ncbi.nlm.nih.gov/articles/PMC8005219/ ↩

  13. Pramhas S, et al. Oral cannabidiol as add-on to paracetamol for painful chronic osteoarthritis of the knee. Lancet Regional Health Europe, 2023. https://pmc.ncbi.nlm.nih.gov/articles/PMC10682664/ ↩

  14. Berger M, et al. Cannabidiol for treatment-resistant anxiety disorders in young people: an open-label trial. Journal of Clinical Psychiatry, 2022. https://pubmed.ncbi.nlm.nih.gov/35921510/ ↩

  15. Vela J, et al. Cannabidiol treatment in hand osteoarthritis and psoriatic arthritis: a randomized, double-blind, placebo-controlled trial (conference abstract; full paper in Pain, 2022). https://acrabstracts.org/abstract/cannabidiol-treatment-in-hand-osteoarthritis-and-psoriatic-arthritis-a-randomized-double-blind-placebo-controlled-trial/ ↩ ↩2

  16. Taylor L, et al. A phase I, randomized, double-blind, placebo-controlled, single ascending dose, multiple dose, and food effect trial of highly purified cannabidiol in healthy subjects. CNS Drugs, 2018. https://pmc.ncbi.nlm.nih.gov/articles/PMC6223703 ↩

  17. 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/ ↩

  18. Review summarising Hurd et al., American Journal of Psychiatry, 2019 (cannabidiol and cue-induced craving in heroin use disorder). https://pmc.ncbi.nlm.nih.gov/articles/PMC12104536/ ↩

  19. Systematic review of randomised trials of oral cannabidiol and blood pressure in adults (summarising Sultan et al., 2020). https://pmc.ncbi.nlm.nih.gov/articles/PMC13531894/ ↩

  20. 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 ↩

  21. Therapeutic Goods Administration. Australian Public Assessment Report for cannabidiol (Epidyolex). https://www.tga.gov.au/sites/default/files/auspar-cannabidiol-210115.pdf ↩

Common questions

How long does CBD oil take to kick in?

After swallowing CBD oral solution, blood levels peak at about 2.5 to 5 hours. Laboratory studies of single doses for anxiety gave the dose 1.5 hours before testing. CBD is not intoxicating, so there is usually no obvious feeling that it has kicked in.

How long before I notice a difference, days or weeks?

It depends on the condition, and for some conditions trials found no difference at all. In epilepsy trials, seizure rates separated from placebo within the first 1 to 2 weeks. Trials for other conditions typically ran for 2 to 12 weeks before judging the result.

How long before bed should CBD be taken for sleep?

The Australian insomnia trial gave 150 mg under the tongue 1 hour before bed for 2 weeks. On most sleep measures it performed about the same as placebo, so that timing is a description of what was tested, not a recommendation.

How long do the effects of CBD last?

This has not been measured well for symptoms. CBD itself leaves the body slowly, with a half-life of about 56 to 61 hours after a week of twice-daily oral dosing. In one study of people with heroin use disorder, reduced craving was still seen up to a week after three days of dosing.

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.

Didn't find what you needed? Ask us a question.

Keep reading