Last updated: October 2026
CBD bioavailability is the share of a dose that reaches your bloodstream. For CBD swallowed as oil or capsules it’s low, because much is broken down by the liver first. Inhaled CBD reaches about 31%. The biggest thing you can control is food: taking CBD with a high-fat meal raised blood levels about four times in a 2020 trial.
Below: bioavailability by method, what raises or lowers it, whether water-soluble CBD helps, and practical tips.
What is bioavailability?
Bioavailability is the percentage of a substance that enters your circulation unchanged. A dose injected into a vein is 100% bioavailable. CBD you swallow passes through the gut and then the liver, which breaks much of it down before it reaches the rest of the body. That’s called first-pass metabolism.
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View productBioavailability by method
| Method | Bioavailability | Notes |
|---|---|---|
| Inhaled | About 31% (smoking) | Fast, but we don’t recommend inhaling oil. See can you vape CBD oil? |
| Swallowed (oil, capsules, food) | Low; no study has measured it directly in people | Strongly affected by food |
| Under the tongue | Probably similar to swallowed, as most is eventually swallowed | Little direct evidence it’s much higher |
| On the skin | Very little reaches the blood | Acts mainly where applied |
A 2018 review of CBD in humans found only one study had measured absolute bioavailability, for smoking. Figures you see online for oral CBD, such as “6%”, are estimates, not measurements.
What raises or lowers it
| Factor | Effect on CBD levels |
|---|---|
| High-fat meal | About 3.8 times higher than an empty stomach |
| Low-fat meal | About 2.7 times higher |
| Whole milk | About 2.4 times higher |
| Alcohol | About 1.6 times higher. See CBD and alcohol |
| Empty stomach | Lowest levels |
| Some medicines | Can raise or lower levels. See CBD and medication |
These figures come from a 2020 trial of 750mg doses of pharmaceutical CBD. The effect may differ at supplement doses, but the direction is consistent: food helps.
Water-soluble and other formulations
Some products break CBD into tiny droplets so it mixes with water. A 2019 study of a self-emulsifying formula found higher, faster peak levels than standard CBD in MCT oil. That can mean a quicker, more predictable effect, but these products also often contain emulsifiers and cost more. Taking ordinary CBD oil with food closes much of the gap. See water-soluble CBD and best carrier oil for CBD.
How to get more from your CBD
- Take it with or after a meal that contains some fat.
- Hold oil under your tongue for 60 to 90 seconds; it does no harm and may help a little.
- Be consistent with timing and food, so your dose behaves the same each day.
- Don’t raise the dose just because a fasted dose felt weak; try it with food first.
See how to take CBD oil and why isn’t CBD working for me?
The FSA’s 10mg a day figure is precautionary advice rather than a legal limit, set while longer-term safety research continues. At Evopure we think it is a very cautious figure, and many adults use more. If you go above it, increase slowly, and check with your GP or pharmacist first if you take any medication. We don’t recommend our products during pregnancy or breastfeeding.
See also does CBD tea work? for why milk helps CBD absorb in a drink.
Video: what is CBD bioavailability?
A short explainer from the Evopure YouTube channel on what bioavailability means and why it varies.
Related guides
- Black pepper is often paired with turmeric for absorption; see CBD with turmeric and black pepper for what the evidence shows.
- Wondering whether drops beat capsules? See CBD oil vs capsules for what a head-to-head study found.
- Why CBD can seem to stop working, and whether tolerance is the cause.
- For tips on choosing a capsule, see our guide to CBD capsules in the UK.
- For practical timing, see when to take CBD oil and whether to take it with food.
- Taking CBD with milk is one practical example; see CBD coffee for what a trial with whole milk found.
- For how absorption translates into timing, see our guide to how long CBD takes to work.
- An easy way to take CBD with some fat is in a smoothie; see our 6 easy CBD smoothie recipes.
- For how this plays out with sweets and edibles, see do CBD gummies work as well as oil?
- Absorption is only half the story: here is how long CBD stays in your body once it is in, and what its half-life means.
- Taking CBD with fat is one easy step, and making CBD butter is a simple way to do it.
- Under-the-lip CBD pouches raise the same question, since much of what goes into the mouth is swallowed.
- Absorption is only part of the picture: our best CBD oil UK guide covers the lab report, mg per drop and price per mg as well.
- Absorption is a separate question from strength, which our CBD oil strength guide explains in mg per drop.
- For a skin patch example, see Kloris sleep patches and how much CBD each holds.
Sources 4
- Millar SA et al. A systematic review on the pharmacokinetics of cannabidiol in humans. Front Pharmacol, 2018.
- Crockett J et al. Effect of meals, whole milk and alcohol on cannabidiol exposure in healthy subjects. Epilepsia, 2020.
- Knaub K et al. A novel self-emulsifying drug delivery system improving the oral bioavailability of cannabidiol. Molecules, 2019.
- Zgair A et al. Dietary fats and pharmaceutical lipid excipients increase systemic exposure to orally administered cannabis. Am J Transl Res, 2016.
