Even so, Kater says that “most of the literature supports the notion that CBD has better bioavailability when consumed sublingually versus orally. [and] MCT oil-based tinctures are thought to provide better uptake than a traditional oil.” But, again, there’s no evidence that this applies to the exact CBD oil or tincture that you, specifically, have in your cabinet. As mentioned before, every formulation is different, and those small differences matter when it comes to bioavailabilty.
Sublingual delivery isn’t always a better option for all substances, points out Dr. Birdsall—some B vitamins, for instance, need to be “activated” by the liver in order to do their jobs—but for certain vitamins and medications, it can be a super effective delivery method.
To find out—because there’s been relatively little rigorous research on CBD to date and I’m a skeptic by nature—I reached out to a doctor and a scientist for the 411. As I suspected, this isn’t a topic that has been studied in depth. Yet there is some reason to believe that certain CBD products may truly be more bioavailable when absorbed under the tongue than if taken through food or drink.
According to Timothy Birdsall, ND—a member of hemp education platform Prima’s medial advisory group—when you take certain substances sublingually, they can enter directly into your bloodstream, where they’re immediately shuttled to your tissues. Think of it as a shortcut to digestion, which is a longer process in which the substance needs to be ingested, broken down by the stomach, absorbed by the small intestine, and metabolized by the liver. “Not only do many compounds lose potential bioavailability during [the digestion] process, but the time to onset is delayed,” adds chemist Jessie Kater, senior vice president of manufacturing for Curaleaf and Curaleaf Hemp.
After all, if there’s one thing that can be said about the wild west of CBD, it’s that experimentation is key—whether you’re looking for your perfect dose or your perfect delivery method.
How does this apply to CBD? Surprise, surprise: It’s hard to say. “There has been very little scientific research on the sublingual absorption of CBD,” says Dr. Birdsall. The research that does exist has some inconsistencies, adds Kater, since there are so many factors that affect absorption—such as the quality of the CBD or the pH and consistency of the formulation. Plus, many of these studies focus on formulas that contain both CBD and THC—a psychoactive compound found in cannabis that’s supposed to be absent from CBD-only products—so it’s unclear whether their findings would also apply to a product that contains predominantly CBD.
Long story short: You may as well try holding your CBD oil or tincture under your tongue before swallowing it—you could find that you feel it working slightly faster. Anecdotally, says Dr. Birdsall, experts recommended that you hold it there for at least 60 seconds. (A word of warning: There will be drool.) Your other option is to try a product that’s specifically created to be absorbed sublingually, like Kin Slips, which are kind of like those breath-freshening films that dissolve in your mouth.
In an analysis of 14 published studies (nine involving animals and five involving humans), scientists with the University of Montreal concluded that CBD showed promise in treating people with opioid, cocaine, or psychostimulant addiction.
Potential drug-drug interactions with CBD include:
To use CBD oil, place one or more drops under the tongue and hold the dose there for 30 to 60 seconds without swallowing. Capsules and gummies are easier to dose, although they tend to be more costly. CBD sublingual sprays are available as well.
To avoid interactions, tell your doctor and pharmacist about all prescription, over-the-counter, herbal, or recreational drugs you are taking.
CBD oil should be avoided during pregnancy and breastfeeding. A 2018 study from the American Academy of Pediatrics warned women to avoid marijuana during pregnancy due to the potential risks to a baby’s development. Although it is unclear how CBD contributes, CBD is known to pass through the placental barrier.