The World Health Organization describes CBD as “generally well tolerated with a good safety profile”. Many people take it regularly without any problems; however, for some, it can produce side effects.
Understanding the potential risk of side effects is essential to exploring CBD. It will also help you to determine your ideal serving size, as you’ll know when you’ve reached your upper threshold.
The information we’ve gathered in this article has been collected from scientific studies. These studies were undertaken to answer specific questions about CBD, which means the focus is very narrow and focused on certain outcomes.
As a result, there may be side effects that have not yet been studied or reported. We also use anecdotal evidence from our customers and our own experiences to help fill the gaps.
Please note, we are not medical professionals and this article isn’t exhaustive. If you have any concerns or experience any side effects when taking CBD, you should stop taking it immediately and speak to your doctor.
CBD produces slightly different results for each person depending on factors such as health, body mass, body chemistry and age. The same is true of side effects; many people don’t experience any, but some may notice more than one.
The most common are considered to be mild and can include:
Some studies have reported that larger serving sizes may increase the risk of more concerning effects such as:
It’s worth noting that these side effects are rare and typically only seen when consuming large servings of CBD. In our experience, we rarely hear of a customer complaining of these side effects, likely because they are taking CBD well within the daily recommended limits.
On rare occasions where individuals take too much – either intentionally or accidentally – they may have a reaction, but this is likely to be short-lived and mild.
To understand the risks of these side effects, it’s important to know more about how they were discovered. It’s also useful to find out what is known about the causes of these side effects.
The glands that produce saliva are also home to cannabinoid receptors.
When you take CBD, it interacts with these receptors, which makes it harder for them to activate the chemical signals to keep producing saliva.
Most CBD products spend very little time in your mouth, so this effect will likely be mild. If you do experience a dry mouth, take a drink of water after you have taken the oil. This will help keep your mouth fresh and get the saliva flowing again.
Some studies have reported that large amounts of CBD can produce discomfort, diarrhoea and vomiting. No feature of CBD has yet been pinpointed as the cause of these problems; the current theory is that some people’s digestive systems can’t process the oil.
It’s also likely that these problems could be as a result of higher concentrations, or of other ingredients included in the oil. Hemp seed oil and MCT oil are commonly mixed with CBD to act as a carrier; the coconut in MCT oil known to cause mild discomfort in some people and even diarrhoea.
One of the main studies that linked CBD to diarrhoea looked at the effect of the drug Epidiolex on people with epilepsy. 19% of the participants reported diarrhoea as a side effect.
However, they were receiving measures of up to 50mg of CBD per kg of body weight per day, so the high concentration could have been a factor. To put this in perspective, most people take between 20-60 mg of CBD per day.
A 2017 review of clinical data found that CBD often results in appetite changes. For some, it was an increase, while for others it decreased.
It’s likely that these changes could affect your weight over a longer period. It’s worth noting that most of the studies that reported these findings involved children and used daily amounts of more than 150mg of CBD.
CBD has been found to interact with several medications. In most cases, it either slows down or speeds up the metabolism of the medicine, particularly those that interact with the CYP450 enzyme.
This can have a significant impact on how the medicine works, so the Food Standards Agency doesn’t recommend CBD for anyone taking medication. CBD can also interact with some herbal supplements, including St John’s wort. If you have a medical condition or take pharmaceutical drugs, you must speak to your doctor before using CBD.
In 2019, research conducted with mice found that when they were given CBD regularly, some showed increased levels of enzymes that are used as an indicator of liver damage. However, the damage occurred after regular amounts of CBD that are equivalent to a human taking a serving size of between 900mg and 1300mg per day.
In 2020, the Food and Drug Administration (FDA) conducted a review of the CBD-based medication Epidiolex. This is a high-strength, highly refined form of CBD that is only available with a prescription. This alarming study combined the potential risk of high doses of CBD with the potential for poor-quality CBD products being contaminated with unsafe levels of pesticides, heavy metals and THC.
They intended to counter the argument that CBD “can’t hurt”, and the conclusion is that everyone should approach CBD with caution. This includes checking for potential interactions with other medications and being aware of the potential risks and side effects.
While well-intended, the study was picked up by several news outlets and used to suggest that all CBD products cause liver damage. The truth is, we don’t know if CBD will cause liver damage in individuals, but the evidence appears to suggest that the daily dose would need to be significantly higher than most people regularly consume.
Even a single measure of highly concentrated CBD can relax the walls of blood vessels reducing blood pressure. If it drops too low, it may cause dizziness and other complications. So, anyone with existing low blood pressure should check with their doctor before adding CBD to their daily routine.
The study that found this used 600mg of CBD, but some consumers have reported signs of low blood pressure after smaller amounts.
CBD is not known to cause an allergic reaction; however, not all CBD products are produced in the same way. From brand to brand, they’re likely to contain different carrier oils, flavours, additives and other additional ingredients.
Before you try a new product, make sure you know exactly what it contains and check if it has come into contact with any allergens during production. Get to know the brand and make sure it has a reputation for quality and safety.
Look for information about where they source their ingredients and if necessary, contact them to get details about their manufacturing practices.
It’s also possible that you could be sensitive to certain terpenes that are left in your CBD product to enhance the “entourage effect”. Terpenes like linalool and pinene are known allergens, and these are commonly present in CBD.
As a side note, if you have allergies and are taking antihistamines to deal with them, be aware that CBD could increase the concentration of medication in your bloodstream. This is particularly important to know if you use the type of antihistamines known to cause drowsiness, as this could increase the effects.
Commonly reported side effects include light-headedness and dizziness, which could be interpreted as a kind of headache. This study of CBD and headaches suggests that headaches caused by CBD might have more to do with taking too much or taking poor-quality CBD.
Poor labelling practices could lead to individuals taking more CBD than they anticipated. And contamination of the finished product with solvents, heavy metals and pesticides could also result in headache symptoms.
In general, headaches are not a common side effect of CBD use, and we haven’t heard this complaint from customers using CBD within the daily recommended limits.
This list is not exhaustive and there are many areas of CBD and its effects that need further study. Several other side effects such as irritability, fatigue and drowsiness have been reported anecdotally but have not yet been reported in scientific research.
It’s also important to follow the latest guidance from the Food Standards Agency which states:
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We are a small but mighty team of experienced natural health researchers. We follow strict selection criteria and test everything we retail: from ground-breaking food supplements to natural skincare products. Our main area of expertise is CBD.