The Side Effects Of CBD

Updated: Jul 2, 2019

By Alice Rossiter 19th June 2019

The side effects of CBD

Given the ever-rising popularity of cannabidiol (CBD) products around the globe, scientists are keen to demonstrate (or rule out) potential side-effects associated with its use.

With most studies of CBD still at early stages, it’s a research area with a question mark hanging over its head, despite overwhelmingly positive results and an impressive safety profile, to date.

Nonetheless, exploring and documenting side-effects of any medicine or product is critical to protecting the consumer and developing a long-term safety profile. It’s not something we should shy away from or try to ‘sweep under the mat’.

Here, we’ll look at potential side-effects of CBD oil, as well as how to go about buying high-quality products to ensure your health comes first.

What is CBD?

Before we look into reported side-effects of CBD and how they may be managed, it’s good to know what it is and how it works.

CBD is one of 104 chemical compounds known as cannabinoids found in the cannabis or marijuana plant, Cannabis sativa, and the most promising in terms of health benefits. Tetrahydrocannabinol (THC) is the main psychoactive chemical within the plant, which is responsible for the 'high' feeling you get when you smoke or consume it. But not all chemicals within the cannabis plant are psychoactive. Cannabidiol (CBD) is a non-psychoactive chemical produced by the plant and boasts a range of health benefits once carefully extracted. CBD is an appealing option for those who are looking for pain relief or to reduce other symptoms of certain health conditions, without the mind-altering effects of marijuana or certain pharmaceutical drugs.

CBD works by interacting with your endocannabinoid system (ECS). Put simply (trying to avoid as much medical jargon as possible), it increases the effect of endocannabinoids (cannabinoids that are produced naturally in your body) to help regulate various functions of the ECS, such as pain, inflammation, mood, sleep and appetite.

Is CBD safe to use?

There are many studies that show CBD to be effective in treating various health conditions. Most of these studies conclude that CBD is safe and well tolerated, with minimal side-effects. Those that have been documented are usually mild and temporary. A review paper on the safety and side-effects of cannabidiol by the National Center for Biotechnology Information (NCBI) suggests that controlled CBD administration is safe and non-toxic in both humans and animals.

More prominent side-effects have often been attributed to inappropriate dosing or buying poor-quality CBD products that may contain THC or other unwanted chemicals.

Although CBD is generally well tolerated and considered safe, it can cause adverse reactions in some people. If you’re using CBD oil, or considering it, it’s worth being aware of what side-effects can occur and what danger they may pose, if any.

Dry mouth

One reported side effect of CBD is an unpleasant dry sensation in your mouth, also referred to as ‘cotton-mouth’. It’s thought that this is caused by the involvement of the ECS inhibiting saliva secretion. In 2006, a study showed that cannabinoid receptors (type 1 and 2) are present in the submandibular glands, which are responsible for producing saliva. The activation of these receptors can alter saliva production, leading to a dryness in your mouth. However, dry mouth is not thought to be dangerous in any way and likely to just make you feel a bit thirstier.


Some people report getting diarrhoea from using CBD oil, which may seem a little odd considering it’s often used to ease symptoms of irritable bowel syndrome (IBS) and similar gastrointestinal issues. When CBD binds to the CB1 receptor in your endocannabinoid system (ECS), it usually reduces excessive gastric acid, increases blood flow to your stomach lining and aids digestion.

Diarrhoea associated with CBD use is most likely caused by other ingredients in the oil or perhaps if it’s a poor-quality product. The issue might be the carrier oil. Numerous carrier oils can be used in CBD products, including MCT, emu, olive, hemp seed and grapeseed oil, which some people may react to in this way.

Another possible cause of diarrhoea could merely be a standard reaction in the body, similar to when you take a new medicine or visit a warmer climate – your body is simply reacting to the change in its balance and biochemistry.

Changes in appetite

Smoking marijuana is notorious for causing hunger, more commonly referred to as ‘the munchies.’ But CBD oil actually has the opposite effect and often suppresses hunger. For many people, it creates a noticeable reduction in hunger, especially during the day, in between meals. This, in turn, can change your eating patterns, making you eat less overall or simply smaller portions.

Again, this is not a side-effect that has caused many people great worry or danger; and stopping use of CBD oil will return your appetite to its usual pattern.

Low blood pressure

Studies have shown that higher doses of CBD oil can cause a small drop in blood pressure as a result of the vascular relaxant properties it holds. This is usually seen quite quickly after CBD enters your system. This drop can also make you feel lightheaded – another reported side-effect of CBD. If you’re taking any type of medication for blood pressure, or have any problems with high or low blood pressure, you should talk to your GP before taking CBD. It might be that CBD isn’t a good option for you in this case.

This side-effect of CBD is temporary and often occurs in those who take a higher dose. If you feel light headed, sit down, have a tea or coffee, and it usually resolves.


Similar to diarrhoea, some people report that ingesting CBD oil causes mild stomach discomfort and nausea. Again, this is odd considering that CBD is often used to help relieve nausea. It may be the carrier oil or the quality of the product that is causing this. If you do happen to feel nauseous after ingesting CBD, decrease your dose, swap your product or stop using it.

Sleepiness or drowsiness

Not the most surprising side-effect, seeing that CBD is often used as a sleep aid and to help those who suffer with chronic insomnia. At low doses, CBD oil can help you feel less anxious and reduce any pain – both things that may cause or contribute to insomnia. However, at higher doses, CBD can cause drowsiness. Be careful what dose you take and don’t use CBD before driving or operating heavy machinery.


CBD oil has been shown to treat headaches and migraines, easing the symptoms or reducing the frequency of them. But if you experience a headache as a side-effect of CBD, it’s likely that the product you’ve purchased is of poor-quality or it contains solvents, such as ethanol and isopropanol. If headaches appear as a side-effect, do your research and switch to a high-quality, hemp-based CBD oil. It’s also worth bearing in mind that while some people benefit from CBD, we are all unique in our make-up and persistent headaches may indicate that CBD oil is not for you.

Worsening of Parkinson’s disease tremors

Some early research has suggested that taking high doses of CBD might make muscle movement and tremors worse in people who have Parkinson’s disease. Yet at the same time, there are studies that suggest that CBD is safe and well tolerated by patients with this condition.

If you or a loved one has Parkinson’s disease and are keen to try CBD to ease the symptoms, talk to your GP first. It’s recommended that you start with a low dose, as the worsening of muscle tremors has only been recorded in high-dose users. However, this is an under-researched area, and no firm conclusions can be drawn about the true effect CBD has on those with Parkinson’s, regardless of the positive anecdotal stories that continue to emerge.

Interactions with other medications

CBD is known to interact with several medications, including anticoagulants (blood thinners) and some anti-epileptic drugs. If you take any form of regular medication, it’s important to talk to your GP before using CBD oil.

CBD can inhibit the activity of some enzymes found in your liver that are responsible for metabolising pharmaceutical drugs. To explain more, most drug metabolism occurs in your liver, although some processes can take place in your gut wall, lungs and blood plasma. The liver hepatocytes (the chief functional units of your liver) contain all the necessary enzymes for the metabolism of drugs. The main enzymes involved in this metabolism belong to the cytochrome P450 group.

If someone takes high doses of CBD, it can temporarily neutralise the activity of P450 enzymes and therefore alter the way a drug is metabolised by the body.

Incorrect labelling and poor-quality products

If you’re thinking of using CBD oil to treat a health problem, make sure you do your research and source high-quality products from reputable companies. Preferably ones who known exactly where their hemp is grown and the conditions it’s grown under.

A big issue is that CBD oil products are mostly unregulated. There’s no guarantee that a product you purchase online contains a safe or effective level of CBD. In fact, a study published in 2017 found that nearly 70 percent of all CBD products sold online had incorrect labelling in relation to the content. This can obviously cause harm – and many people who experience side-effects can attribute these to a poor-quality product.

Some CBD oils may also contain certain amounts of THC, but is not correctly stated on the label. Other compounds can also be present in CBD oil, which are not labelled on the product. This is a grave concern in a mostly unregulated area; sourcing high-quality hemp products is key to reaping the benefits from CBD.

In another study, more than a quarter of 84 products purchased online contained less CBD than labelled. In addition, THC was found in 18 of these products. THC can increase your heart rate, cause dizziness, hallucinations, paranoia and make you feel ‘stoned’. They may also interact with other drugs.

Issues with dosing

Yes, CBD oil is natural, but you’re likely to experience certain side-effects if you take too much, as with any product you consume. That includes regular food! It’s easy to over consume CBD oil – several drops may not seem like much to some people. But it’s important to remember that large amounts of hemp go through the extraction and purification process to create CBD oil. It's important to research optimum dosage for your condition and start with a low dose to see how you’ll react.

Guidelines to buying CBD products online

You only need to spend several minutes on the internet to appreciate the range of CBD products available to purchase online. Help reduce your chance of unwanted side-effects. Here are three things to consider when buying CBD oil products.

  • Check the purity. The oil should be 50 percent CBD or more, with no or only trace amounts of THC. Look for statements like ‘Zero THC’ and ‘THC free’. Always check the label again once you receive your product.

  • Check the source. It’s currently recommended that you only buy CBD oil that has been manufactured in Canada, Europe or the USA. These areas have strict regulations and guidelines around manufacturing hemp and will help ensure you purchase a high-quality product.

  • Avoid cheap CBD oil. It’s tempting to save a few pennies. But like many things in life, you have to pay a little more for good quality products. You’re going to ingest this product, it’s for your health – and nothing is more important than that.

Although research into CBD is still at early stages, the studies we have seen, to date, show an excellent safety profile and much promise for many health conditions. Side-effects are mostly mild, temporary and often occur due to poor-quality products or ingesting high doses. Seek quality oil, don’t be afraid to ask the supplier their source and stop using any product that causes you unwanted side-effects.

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