CBD is becoming increasingly popular, with shops selling CBD oil, edibles, and vape juice in most cities where it's legal. Some companies even sell CBD capsules. But if you're looking to take advantage of CBD's stress-reducing, sleep-enhancing, or pain-relieving properties, not all products work the same way.

While edibles offer a smoke-free method of ingesting, they don't deliver the biggest or fastest effect per milligram of CBD. That's because they need to pass through the digestive tract and the liver before making it into your bloodstream and ultimately your brain, said James Giordano, professor of neurology and biochemistry at Georgetown University Medical Center.

When CBD, including in capsule form, passes through your liver, it'll get metabolized, so not everything will make it to your brain, Giordano said.

One study found that the bioavailability, or the amount that enters the bloodstream, of CBD taken through an edible was only 6 percent.

The potency of CBD oil, on the other hand, will depend on how you're ingesting it. When it's swallowed, the process is the same as edibles, taking the long and winding route through your liver before its effects set in.

However, some CBD oils can be applied under your tongue, where it gets straight into your bloodstream, yielding a faster and stronger effect, because the CBD doesn't dilute through the digestive process.

“Anything that's directly absorbed from the mouth will have a much higher potency and therefore a somewhat greater effect on the brain,” Giordano told Marijuana.com.

The effectiveness of vaping CBD oil also varies based on your inhaling technique. If you inhale and then swallow the air, that brings some of the CBD through your gastrointestinal tract and liver before it enters your bloodstream, Giordano said. But if you inhale it into your lungs, the way you would a cigarette or joint, your blood vessels should absorb the active ingredients right away. One study found that the bioavailability of CBD was 31 percent when inhaled.

CBD interacts with the CB2 receptors in your endocannabinoid system. These regulate many functions including, which regulate many functions, particularly the immune system, which can allow CBD to reduce inflammation. CBD has also been shown to interact with 5-HT1A serotonin receptors, which can help reduce anxiety. It can carry side effects including “dry mouth, low blood pressure, lightheadedness, and drowsiness,” according to WebMD. It may exacerbate symptoms of Parkinson's disease, and it's unclear whether it's safe for pregnant or breastfeeding women.

How you ingest CBD won't change the type of effect it has on you; it can affect the intensity and the speed at which you absorb it.

If you want high intensity and immediate absorption, go for oil under the tongue or inhalation directly into the lungs. If you can wait or want a more subtle effect, on the other hand, swallowed oil, edibles, and capsules should work just fine.