CBD Supplements

Isolation and early chemistry

A 2014 expert review in Epilepsia describes cannabidiol (CBD) as the major nonpsychoactive ingredient of cannabis, in contrast to delta-9-tetrahydrocannabinol (THC), the major psychoactive ingredient. The same review states that CBD was isolated in 1940 and that its structure was elucidated in 1963. The article does not name the chemists in that sentence, so this page does not attribute the work to individuals.

The World Health Organization (WHO) Expert Committee on Drug Dependence describes CBD as one of the naturally occurring cannabinoids in cannabis plants. It is formed from a precursor, cannabidiolic acid, after decarboxylation, and it can also be produced synthetically.

From clinical interest to a consumer market

By 2014, the Epilepsia review noted a lack of well-powered, double-blind, randomized trials of pure CBD for any disorder, and said that trials in Dravet and Lennox-Gastaut syndromes were being planned. A 2017 review reported that adequately powered placebo-controlled trials of CBD in epilepsy had only recently begun, after years of case reports, small series and surveys.

The WHO committee's 2018 critical review noted unsanctioned medical use of CBD-based products, with oils, supplements, gums and high-concentration extracts available online for many ailments. A 2024 toxicology review by U.S. Food and Drug Administration (FDA) scientists describes widespread use of non-pharmaceutical CBD products and rising sales, accompanied by concerns about unsubstantiated benefits and a lack of quality control. The sources reviewed do not give a date for the start of the wellness market.

CBD, THC and cannabis

CBD and THC are different compounds found in cannabis. NCCIH, part of the U.S. National Institutes of Health, uses cannabinoids as the broader group name, and notes that CBD may also produce psychotic effects or cognitive impairment in people who also regularly use THC. Reviews of medical cannabis often group whole-plant products, THC-containing medicines and plant-derived isolates together, so a finding about cannabis or a THC and CBD combination is not a finding about a CBD-only supplement.

Cochrane reviews use the term cannabis-based medicines for herbal, plant-derived and synthetic products. In the neuropathic pain review, most of the included studies tested an oromucosal spray combining plant-derived THC and CBD, not CBD alone.

Prescription CBD and supplement products

The FDA states that it has approved one CBD prescription drug, Epidiolex, for certain severe seizure disorders. NCCIH names these as seizures associated with two epileptic encephalopathies, Lennox-Gastaut syndrome and Dravet syndrome. The FDA says other CBD products have not been evaluated for effectiveness, dosing, drug interactions or safety.

Retail labels such as full-spectrum, broad-spectrum and isolate describe which other cannabis compounds a product contains. None of the scholarly or government sources reviewed defines these terms, so this page does not give a standard meaning for them. Bonn-Miller and colleagues found unlabeled compounds, including THC, in some products, which is relevant to any such label.

Forms in which CBD is sold

Studies and reviews describe CBD wellness products as oils, tinctures, vaporization liquids, supplements, gums and extracts of varying concentration. A 2017 study that bought products online grouped them as oil, tincture or vaporization liquid. This page does not list brands, formulations or amounts, and the sources reviewed do not catalog capsules, gummies or topicals as separate categories.

What is known about how CBD acts

The Epilepsia review states that the antiepileptic mechanisms of CBD are not known, and lists candidate targets including a nucleoside transporter, the receptor GPR55, a vanilloid channel, the 5-HT1a receptor and glycine receptors. A 2024 pharmacology review adds that CBD is metabolized in the liver and is described as a known cause of enzyme-mediated drug interactions.

These mechanism statements come from laboratory and animal work as well as human studies and do not establish that a consumer product produces any particular effect in a person. They also describe CBD as a single compound, whereas retail products vary in what else they contain.

Uses reported for supplements

The WHO committee noted online sale of CBD products for the treatment of many ailments. Systematic reviews have examined CBD in anxiety, sleep, psychosis, mood disorders, substance use and chronic pain, and the Epilepsia review lists anxiety, schizophrenia, addiction and neonatal hypoxic-ischemic encephalopathy as areas where CBD bears investigation. Being studied does not mean an effect has been shown.

Claims made about products

The FDA states that some CBD products are marketed with medical claims that have not been supported, and that such claims could lead consumers to delay necessary medical care. The 2024 toxicology review similarly refers to unsubstantiated benefits. This page reports what the evidence sources found, not what product sellers state.

Established medical use: certain severe epilepsies

The established medical use is a pharmaceutical oral CBD solution, added to existing seizure medication. In a randomized, double-blind, placebo-controlled trial of 225 patients aged 2 to 55 with Lennox-Gastaut syndrome, drop seizures fell by a median of 41.9 percent and 37.2 percent in the two CBD groups, versus 17.2 percent with placebo, over 14 weeks. Common adverse events were somnolence, decreased appetite and diarrhea, and 14 patients taking CBD (9 percent) had elevated liver aminotransferase levels. The trial was funded by the manufacturer.

A 2017 review concluded that phase 3 trials of this product support efficacy and an adequate safety profile in children with Dravet and Lennox-Gastaut syndromes. The same authors state that valid data on safety, efficacy and dosing are lacking for artisanal preparations and online CBD sources, and NCCIH states that research on other, more common epilepsies is insufficient. This evidence concerns a prescription medicine and is not carried over to supplements.

Anxiety, sleep, psychosis and addiction

A systematic review of randomized trials of CBD in psychiatric disorders included 27 articles and concluded that evidence on safety and efficacy is limited, with potential effects reported for substance use disorders, chronic psychosis and anxiety. A separate clinically focused review judged it premature to recommend cannabinoid-based interventions, reporting tentative support for CBD in social anxiety, mixed evidence as an add-on in schizophrenia, and weak evidence from case studies for sleep.

The 2017 National Academies report rated the evidence for CBD improving anxiety symptoms in social anxiety disorder, measured by a public speaking test, as limited. NCCIH describes the underlying study as including 24 people. For sleep, NCCIH states it is uncertain whether cannabis products affected sleep directly, and effects in people without other illnesses are uncertain.

Pain and inflammatory conditions

The National Academies report describes conclusive or substantial evidence for cannabis in adult chronic pain, but its label refers to cannabis, not CBD. A Cochrane review of cannabis-based medicines for chronic neuropathic pain included 16 studies with 1,750 participants, most testing a THC and CBD spray, and concluded that potential benefits might be outweighed by potential harms.

A 2023 Cochrane review of cancer pain included 14 studies with 1,823 participants. It reported low-certainty evidence, from one study of 144 people, that CBD oil did not add value to specialist palliative care alone in reducing pain. The sources reviewed contain no human trial evidence on CBD for inflammatory conditions, and the Epilepsia review describes anti-inflammatory effects only as laboratory findings.

Quality of the wellness evidence

Reviewers describe small samples and limited numbers of trials outside epilepsy. The clinically focused review cautioned that small sample sizes mean the data should be read with caution, and the WHO committee called the evidence for other conditions preliminary.

Studies of mislabeled products

Bonn-Miller and colleagues bought 84 CBD products from 31 companies in a 2016 online search and tested them in a laboratory. Using a margin of 10 percent, 26 products (30.95 percent) were accurately labeled, 36 (42.85 percent) contained more CBD than labeled and 22 (26.19 percent) contained less. Vaporization liquids were the most often mislabeled and oils the most often accurate.

THC was detected in 18 of the 84 products (21.43 percent), at concentrations up to 6.43 mg per mL. This is a single study from one year and one purchasing method, and it should not be generalized to all current products.

Health body statements on quality

NCCIH states that over-the-counter CBD products may contain more or less CBD than stated on their labels and may contain contaminants such as THC. The FDA states that its testing found many products did not contain the CBD levels claimed, and that it is investigating reports of contaminants including pesticides and heavy metals.

Common effects and liver findings

Reported effects include drowsiness, reduced appetite and diarrhea, and NCCIH adds reduced alertness and mood changes. The FDA states that CBD can cause liver injury and that this could go undetected without monitoring by a health care provider.

In a long-term epilepsy study of 607 patients cited in a 2024 review by FDA scientists, 61 (10 percent) had ALT or AST above three times the upper limit of normal, and 46 of those 61 were also taking valproate. That review also reports liver enzyme rises in healthy adults taking high doses over several weeks, and states that it is not a risk assessment. Liver findings at doses used in epilepsy trials cannot be applied to a given supplement, and the reverse also holds.

Drug interactions and other toxicology

The same review reports that CBD inhibits several cytochrome P450 enzymes, with the strongest effect on CYP2C19. In 13 children, levels of a clobazam metabolite rose and clobazam doses were reduced, and a single case report described rising INR in a person taking warfarin. FDA scientists also report that CBD inhibits certain transporters, and that animal studies show reproductive and developmental toxicity, including in males.

Pregnancy, breastfeeding and THC content

The FDA advises against using CBD, THC and marijuana in any form during pregnancy or breastfeeding. It states that there is no comprehensive research on CBD in these settings, that high doses of CBD caused reproductive problems in developing male animals, and that some CBD is expected to pass to infants through breast milk. It also notes that CBD products could be contaminated with substances including THC.

Abuse potential, driving and workplace issues

The WHO committee reported that in humans CBD showed no effects indicative of abuse or dependence potential, and that there was no evidence of public health problems associated with use of pure CBD. It also noted that controlled human studies of physical dependence had not been reported. This finding concerns pure CBD, while the product studies above found THC in some retail products.

NCCIH links cannabis use to a higher risk of motor vehicle crashes but does not address CBD specifically. A 2020 psychiatric review notes that workplace drug tests can detect THC long after impairment has ended. The sources reviewed contain no health-body statement specific to driving or workplace use of CBD supplements.

Care boundary

This page is information only. The FDA warns that unsupported claims about CBD products may lead people to delay necessary medical care, and the 2017 epilepsy review states that adequate medical oversight is indicated for seizure disorders rather than unsupervised use of unregulated products. A person taking prescription medicine, or who is pregnant or breastfeeding, would need to discuss any CBD product with a health care provider.