CBD oil is a plant-derived product made by extracting cannabidiol, one of over 80 active compounds in the cannabis plant, and diluting it in a carrier oil. Unlike THC, the compound responsible for marijuana’s high, CBD does not produce intoxication or impairment. In human studies, oral doses up to 300 mg and injected doses up to 30 mg were perceived as inactive by participants, meaning they couldn’t feel any psychoactive effect at all.
How CBD Differs From THC
CBD and THC come from the same plant and share a similar chemical structure, but they behave very differently in the body. THC activates a receptor in the brain called CB1 with high potency, and this activation is what produces the feeling of being high. CBD binds poorly to that same receptor. Instead of switching it on, CBD actually changes the receptor’s shape slightly, making it harder for THC and the body’s own cannabis-like molecules to activate it. This is why CBD doesn’t cause euphoria, impaired coordination, or the other effects people associate with marijuana.
How CBD Works in the Body
CBD’s effects aren’t limited to a single receptor or pathway. It interacts with the body’s endocannabinoid system, serotonin system, and opioid system simultaneously. Within the endocannabinoid system, it acts as a kind of dimmer switch rather than an on/off button, subtly modulating signals rather than flooding receptors the way THC does. Its influence on serotonin pathways is one reason researchers have studied it for anxiety, while its broader activity across multiple systems helps explain why people report such varied effects.
Types of CBD Oil
Not all CBD oil contains the same mix of compounds. The three main types reflect how much of the original plant material ends up in the final product.
- Full-spectrum contains all the plant’s natural compounds, including other cannabinoids, terpenes (aromatic compounds that contribute to flavor and may have their own effects), and up to 0.3% THC. This tiny amount of THC is not enough to produce a high but could potentially show up on a very sensitive drug test.
- Broad-spectrum keeps most of those plant compounds but removes nearly all the THC.
- CBD isolate is pure cannabidiol with no other cannabinoids or terpenes. It’s the most processed form and contains no THC whatsoever.
Some people prefer full-spectrum products based on the idea that the plant’s compounds work better together, sometimes called the “entourage effect.” Others choose isolate specifically to avoid any trace of THC.
How CBD Oil Is Made
The most common high-quality extraction method uses pressurized carbon dioxide. CO2 is pumped into a chamber containing hemp plant material, and when the pressure and temperature reach a specific range, the gas enters a “supercritical” state where it behaves like both a liquid and a gas. In this form, it pulls CBD, terpenes, and other beneficial compounds out of the plant while leaving behind waxes, chlorophyll, and debris. The process is clean enough that it’s FDA-approved for use in food and beverage production, and because it runs in a closed loop, the CO2 is recycled.
Cheaper products sometimes use ethanol or butane extraction instead. Ethanol tends to pull out too much chlorophyll, giving the oil a grassy, bitter taste. Butane extraction can leave behind solvent residues if not done carefully. Both methods are less precise, extracting a broader mix of wanted and unwanted compounds.
How You Take It Matters
The way you consume CBD dramatically affects how much actually reaches your bloodstream. Swallowing a CBD capsule or edible delivers only about 9 to 13% of the CBD to your system, because much of it gets broken down in the gut and liver before it can circulate. It also takes 30 minutes to 2 hours to feel any effect.
Holding CBD oil under your tongue (sublingual use) bumps absorption to roughly 12 to 35%, because some of the CBD passes directly through the thin tissue under the tongue and into the bloodstream, bypassing the digestive system. Inhaling vaporized CBD offers the highest bioavailability at around 31 to 45%, with effects arriving within minutes. Topical CBD products applied to the skin have the lowest absorption rate, typically just 1 to 10%, which is why they’re used for localized areas rather than whole-body effects.
Newer formulations are trying to close this gap. Some specialized oral capsules have achieved bioavailability in the 31 to 34% range, comparable to inhalation, by using gelatin-based delivery systems that protect the CBD through digestion.
The One FDA-Approved CBD Medication
As of now, only one CBD-based drug has earned FDA approval: Epidiolex, a purified form of cannabidiol used to treat seizures. It’s approved for three specific conditions: Lennox-Gastaut syndrome, Dravet syndrome, and tuberous sclerosis complex, all in patients one year of age and older. These are severe, often treatment-resistant forms of epilepsy. No other CBD product has been approved by the FDA for any medical condition, which means the CBD oils sold in stores and online are marketed as supplements, not medications, and aren’t held to the same standards for purity or dosing accuracy.
Side Effects
CBD is generally well-tolerated, but it’s not side-effect-free, especially at higher doses. Clinical trials across multiple conditions have documented a consistent pattern. The most commonly reported effects are diarrhea, drowsiness, fatigue, and changes in appetite. In a trial for Lennox-Gastaut syndrome, 86% of treated patients experienced some adverse effect, with diarrhea (about 19%), drowsiness (14%), decreased appetite (13%), and fever (13%) being the most frequent. A Parkinson’s disease trial using higher doses saw even higher rates: diarrhea in 85% of participants, drowsiness in 69%, and fatigue in 61%.
Liver enzyme elevations have also appeared in clinical data, particularly at higher doses. In the Parkinson’s trial, 39% of participants showed changes in liver function tests. This doesn’t necessarily mean liver damage, but it signals that the liver is working harder to process the compound.
Drug Interactions to Know About
CBD is processed by the same liver enzymes that break down many common medications. A study evaluating twelve cannabinoids found that nearly all of them inhibited one particular enzyme pathway (CYP2C9) at concentrations relevant to normal CBD use. This enzyme is responsible for metabolizing several widely prescribed drugs, including certain blood thinners and anti-seizure medications. When CBD slows down this enzyme, those medications can build up to higher-than-expected levels in the blood, potentially intensifying their effects or side effects.
Other major drug-processing pathways were either unaffected or only partially inhibited by cannabinoids, so the interaction risk isn’t universal. But if you take any medication with a narrow margin between an effective dose and a harmful one, CBD’s effect on liver enzymes is worth taking seriously.