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Cannabidiol (CBD) Oil Side Effects

What is CBD? 

CBD is a relatively new phenomenon with a plethora of health benefits, both physiological and psychological.

CBD is the non-intoxicating extract from the cannabis sativa plant that does not have the psychoactive properties of THC. CBD oil is made up of a mixture of CBD infused with an inert carrier oil like coconut oil, MCT oil or hemp seed oil. The bottled oil often referred to as a tincture can be sold in an array of concentrations, flavours and sizes. You can also purchase CBD in many other forms, such as CBD CapsulesCBD Spraystransdermal CBD PatchesTopical CBD Skin care products and CBD vapes. For CBD to be legal in the UK there cannot be any THC contained within the product as THC is a controlled substance. 


How does CBD work in the body?

CBD affects the body by interacting with the Endocannabinoid System (ECS). The endocannabinoid system is a complex network is a network of receptors & neurotransmitters spread throughout the human body. The body naturally produces compounds similar to hormones called endocannabinoids to interact with this system. Phytocannabinoids, phyto means “from plants”, are very similar to endocannabinoids, this allows phytocannabinoids to interact with the endocannabinoid system too.

The endocannabinoid system is responsible for controlling the majority of biological processes throughout the body and brain. Memory, cognitive functions, pain, mood, immunity and temperature levels are all aspects of anatomy that are controlled by the endocannabinoid system. The primary reason that human beings have an endocannabinoid system is for homeostasis which is responsible for maintaining chemical balance throughout the body.


Clinical Evidence from CBD trials

Those who criticise CBD state that there is not currently enough clinical evidence for CBD to be recommended for many of the conditions and ailments CBD is said to treat effectively. The CBD community needs to work to build a tremendous amount of preliminary scientific evidence from lab tests, animal studies and case studies. Numerous scientific papers are published each year containing research in CBD and the effects it has on the body. The safety and efficacy of CBD are the two most crucial points that need to be proven for CBD to be truly accepted as a treatment for things like anxiety and chronic pain. It will still be a number of years before there is hard clinical evidence to support the benefits CBD can provide for different conditions.


What are the health benefits of CBD?

CBD can help people deal with an array of symptoms and conditions. From skin conditions like acne and eczema to psychological issues like anxiety and depression. Many chronic pain sufferers swear by CBD.

There is evidence that CBD oil can be used to alleviate symptoms such as painanxiety, stimulate appetite and shows promise in being prescribed to treat certain types of seizures. Epidiolex is a CBD oral solution that is prescribed to treat rare forms of epilepsy in children.

CBD has a reasonably low affinity for cannabinoid receptors in the brain. The cannabinoid receptors are the molecules that THC binds to cause its psychoactive effects. It is speculated that CBD influences other receptors including opioid receptors that are involved with the regulation of pain. CBD is also thought to regulate glycine receptors which are involved in the secretion of serotonin.

Proponents of CBD oil allege that CBD can treat a wide variety of health problems, including;

  • Acne
  • Anorexia
  • Anxiety
  • Chronic Pain
  • Depression
  • Drug addiction and withdrawal
  • Eczema
  • Epilepsy
  • High blood pressure
  • Insomnia
  • Muscle spasms
  • Migraines

CBD has shown promising signs that it could be a viable treatment for anxiety disorders, as illustrated by this study. Interestingly CBD seems to be more effective in treating anxiety at smaller doses whereas higher does exhibited almost no tangible improvements.


Possible Side Effects

There are instances of clinical research that has shown that CBD oil can trigger side effects, the severity and type of side effect that is exacerbated varies from person to person and there does not seem to be a consistent trend with regard to what side effects CBD causes.

There have been no reports of any serious health damage experienced after the intake of CBD oil by anyone in any part of the world. However, a few minor health conditions have arisen in cases of adverse reactions in a small number of people. Although research is still needed in this area, CBD oil has been associated with side effects such as:

  • Anxiety
  • Changes in appetite
  • Changes in mood
  • Diarrhoea
  • Dizziness
  • Drowsiness
  • Dry Mouth
  • Nausea
  • Vomiting

There has been conjecture that CBD increases liver enzymes which are a symptom of liver inflammation. Those who suffer with liver disease should use CBD oil with caution, ideally with approval from their doctor who can monitor their blood liver enzyme levels.

Using CBD oil when you or your partner are pregnant should be avoided, it is also not recommended that you use CBD oil when you are breast feeding.

A study that was conducted in 2018 that was carried out by the American Academy of Paediatrics warned women to avoid marijuana and cannabis throughout their pregnancy because of the potential risks to the baby’s development. It is not known whether CBD is able to pass through the placental barrier.

It is always recommended that whatever condition you are trying to treat CBD with that you consult your GP or a doctor to ensure that any underlying health issues you have are not negatively impacted by the use of CBD.


Side effects of dishonest CBD products

Clinical studies and trials result in high quality, safe products which contain the amount of CBD that is advertised on the label. 31% of products were inaccurately labelled in a 2017 study. This is a very large part of the market that is selling products that may contain THC, synthetic cannabinoids or even pesticides and heavy metals. There were even instances of products containing no CBD whatsoever.


Interactions with Medication

CBD oil may interact with specific medications, including some prescribed to treat epilepsy. CBD is known to inhibit an enzyme named cytochrome P450 that certain drugs use for metabolisation. Due to CBD’s interference with CYP450, CBD may either increase the toxicity or cause the drugs to be less effective.

Below is a list of potential drug interactions with CBD;

  • Anti-arrhythmia drugs such as quinidine
  • Anti-convulsant such as Tegretol and Trileptal
  • Anti-fungal drugs such as Orap
  • Atypical anti-depressants such as Remeron
  • Benzodiazepine sedatives such as Klonopin and Halcion
  • Immuno-suppressive drugs such as Sandimmune and cyclosprorine
  • Macrolide antibiotics such as clarithromycin
  • Rifampin based drugs that are used to treat tuberculosis

Many of the interactions above are mild and require no adjustment to the treatment the user is on. Other may require a drug substitution or the separation of doses.



The Food Standards Agency (“FSA”) advises that healthy adults do not take more than 70mg of CBD a day. This is about 28 drops of 5% CBD oil. The FSA also stated that CBD may affect the liver if taken in high doses but did not that there is very little evidence to support this.

There are no specific guidelines for the appropriate daily consumption of CBD oil. CBD tinctures are delivered sublingually and there is no definitive correct dose of CBD, with different specialists and suppliers advising anywhere in the range of 5mg to 25mg per dose.

For CBD delivery methods that are taken sublingually, it is recommended that the oil or CBD spray is left to sit underneath the tongue for between 30 and 60 seconds without swallowing or until the oil has dispersed. The bioavailability of the product will affect how long the oil is held under the tongue. For instance, the Cannacares CBD Mint Spray has an extremely high bioavailability and is dispersed in the mouth very quickly and the result is that the onset of the CBD effects are much faster.


Factors that influence dosage

One thing that has yet to be addressed in the CBD community, is definitive doses. Like any other supplement or medication, the dose a person take should depend on several factors such as body weight, sex and age. The reason why CBD is being taken is important too. If it is for a specific condition, a larger dose may be required.

Alcohol and other substances that are central nervous system depressants can induce the sedation effect of CBD. People who use other medicines that cause drowsiness are advised to decrease their dosage of CBD. Before mixing CBD with alcohol or other medications, it is always recommended that you speak to your doctor first.


Contraindications of CBD

When researching CBD, it can be hard to discover any evidence of dangerous side effects or contraindications. CBD is a new phenomenon and the mass adoption of concentrated CBD, so the user’s safety is paramount, and more evidence is required to prove its safety.



There is still a tremendous amount of research that needs to be conducted into the efficacy and the safety of CBD and the various delivery methods that can be used to consume CBD. The latest Novel Food regulations throughout Europe will mean that there is greater scrutiny on the industry and that all ingestible products must be approved by the FSA as of the 31st of March 2021. This will result in every ingestible CBD product that is legally for sale in the UK will have toxicity and stability data proving that the product is safe for human consumption and that the ingredients and concentration advertised on the label is the actual components of the product.

The Novel Food legislation means that there will no longer be sub-standard suppliers of raw material. All raw material suppliers will have to ensure that their agricultural and manufacturing practices are of the highest standard otherwise their Novel Food application will be rejected, and they will be unable to white label or produce ingestible CBD products for the UK and European market.

The UK CBD market is becoming fiercely competitive and as the market grows, the dominant companies will become more sophisticated and will try to catch out their competitors if they are not compliant. The FSA have already disclosed that they will actively be removing any CBD products that are not Novel Food compliant or breach any aspect of the new legislation. Therefore, it is within all CBD companies interests to ensure that they are compliant and are distributing high quality products. 

While CBD has been known to cause a few minor side effects, if your doctor confirms that CBD will not interfere with your medication it is worth trying. The potential benefits of CBD can be extraordinary and there are countless instances of first-hand stories about how much of a positive effect CBD has had on people’s lives. Whether it is a chronic pain sufferer or someone who has anxiety issues, CBD has helped many people to deal with their conditions without taking harmful unnatural medication that has side effects which can be intolerable over a sustained period of time.