When it comes to taking CBD there are hundreds of options available in the UK, all promoting
themselves as being the best for your money. Products typically range across oils, E-liquids,
capsules, and pastes, but recently we’ve seen some new additions such as creams and
cosmetics, whole flower, and even staples like coffee beans now come CBD infused. But how
do you know which route to take? Are you really getting good value for money? In this post, we’ll
expand on how to maximise CBDs effectiveness, and give you the information needed to make
an informed decision when buying CBD.

Route of Administration and Bioavailability

One of the main aims of medicines and supplements is to deliver the correct dose of the drug to
your bloodstream, and a quick look at your local pharmacy shows there are many ways to get it
there. The way a drug gets to your blood is known as a route of administration and each has
its own benefits and level of effectiveness. The total amount that gets into the blood is
referred to as bioavailability and is represented by a percentage. 100% bioavailability means
ALL of the substance you take makes its way to the blood. Low bioavailability of 10% means if you
take 100mg of CBD, only 10mg will actually get put to good use. The remainder is usually
excreted as waste. Below we’ll take a look at some of the more common forms of CBD and their
respective bioavailability.

Oral Capsules

By far the most common route of administration for most drugs, it’s easy to take and usually
comes in the dose you need. Pharmaceuticals tend to be designed for this route and usually
have a high bioavailability. Unfortunately, when it comes to CBD this method of consumption is
one of the worst. With studies showing bioavailability as low as 4% (more modern studies
suggest this number may be closer to 20%), this means if you take a 100mg tablet, between
4mg-20mg will end up where you need it. This is due to a phenomenon called ‘first pass
metabolism’, and its effects on CBD are especially damaging.
Any orally ingested product (CBD which is taken via the gut) therefore should be taken in much
higher quantities or dosage to get the desired effects.


Sublingual basically means ‘under the tongue’. This is a common route of administration for
CBD oils and extracts. Buccal products are grouped in the same category and this refers to the
soft tissue of the cheek area next to your gums.

Both areas are an ideal route of administration for CBD due to the high volume of blood vessels
combined with very thin tissue. This allows the CBD to pass directly into the bloodstream
without having to go through first pass metabolism. These two factors contribute to the much
higher bioavailability – between 12%-35%, a much more efficient route than swallowing a tablet
would provide.


Another common route of administration is inhalation. An age-old method which has been used
historically for the consumption of all types of substance, from asthma inhalers to opium pipes – the
lungs are a popular organ for drug use! CBD products that follow this route include e-liquids,
vaporised products, and smoked products.
Again, this method avoids the problems oral ingestion exhibit, bypassing the stomach and liver
completely. The huge surface area of the lungs gives yet another boost to bioavailability, with
studies putting inhaled CBD absorption at around 35%-55%! That’s more than double you would
get from taking a CBD tablet.

Topical Application

A familiar route of administration for everyone – creams are usually reserved for drugs that need
to work locally on the area applied. Rather than be absorbed by one area of the body and
transported to every cell, they have a direct action on the cells to which they are applied. This
gives creams a very low systemic bioavailability, which needn’t be a problem if they are being
used directly on the site they’re needed; you wouldn’t apply CBD cream to your hand in order to
treat a problem in your foot!
Bioavailability for topicals tends to be lower than 1% as their action is confined to the top 3
layers of skin to which they are applied.
It should be noted that topical products differ significantly from transdermal products, however,
there are almost no transdermal CBD products on the market currently and so will not be
covered here.


By far the most effective route of administration, but equally the least culturally accepted. Very
few people jump at the idea of taking their medicines or supplements rectally, but for those who
need it, it makes for a very effective method. Similarly to the lungs or cheek, the rectum is chock
full of blood vessels designed for absorption (usually of water), with very thin tissue between
blood vessels and exterior cavity. Suppositories can be held against the absorption site for as
long as it takes to dissolve and get absorbed. Bioavailability levels of up to 80% or 90% are not
Given the choice, most people would take a highly ineffective tablet over a highly effective
suppository, and we do not expect the majority of people to do otherwise. Saying that, certain
members of the public can really benefit from the unique characteristics of suppositories. People
undergoing chemotherapy, for example, may suffer from significant nausea and vomiting which
makes it impossible to keep a tablet down.
Suffice to say this route of administration will likely be reserved for special cases, but for those
cases it can be an invaluable tool.