Just a quick disclaimer; we don’t make health claims about CBD, we just share the research. You’ll always find references to scientific literature to substantiate what we share. This is for informational use only. Always speak to your doctor before making any changes to your healthcare regimen.
I bet you’ve been hearing a lotta hype about CBD, because for the most part, its awesome. However, its not all rainbows and lollipops and there’s always two sides to every story. CBD hasn’t been studied all that much, so theres not much gold standard scientific evidence surrounding it.
That being said, there are a few surveys and clinical trials which have reported on the potential side effects that CBD may elicit. There are a few caveats to bear in mind here, though:
- The CBD used in research is not always the same as that publicly sold. Find out about the difference here.
- In clinical research some participants are using other drugs, which may interact with CBD to produce side effects.
- These side effects refer mainly to CBD used orally, not externally on the skin.
In general, CBD is pretty safe. One review of clinical studies with CBD concluded that CBD had a better side effect profile than a handful of prescription drugs used to treat certain conditions (*).
Digestive upset was uncommon in a recent survey of over 3,000 CBD users. Only 4% experienced digestive issues when using CBD (1).
However in clinical research, diarrhea has been reported more frequently when using CBD. 8% of patients using CBD at doses of ~ 450 – 625mg said they had diarrhea. Interestingly, with higher doses of ~ 900mg – 1250mg CBD, 15% of patients experienced diahrrea (2). This is a common trend when higher doses of CBD are used (3), (4), (5), (6), (7).
The key differences here between the survey and clinical research is:
- research uses much higher doses
- research also uses CBD isolate, which is 99% pure CBD.
Most users from surveys report using full spectrum CBD rich extracts. Its estimated that only about 4% of people actually use CBD isolate (1).
Funnily enough, almost 16% of users take CBD to aid gastrointestinal conditions like IBS and IBD. They reported improvements in diahrrea, constipation and indigestion (1).
A clinical trial also found that patients with ulcerative colitis taking a CBD rich extract had significantly greater improvements in quality of life scores compared to the placebo group (8).
Its highly likely that CBD isolate, especially at high doses, has a different effect on gut function than full spectrum extracts.
CBD can have something known as a biphasic effect, which basically means it can produce opposite effects based on whether a low or high dose is used (30). CBD may inhibit or stimulate cannabinoid receptors in the gut based on dose, which influences the rate of bowel movements.
It may be that especially high doses of CBD produce diahrrea, whereas lower doses prevent it. Using CBD isolate may also cause more diahrrea (9).
Appetite & Body Weight
Increases in appetite did not translate into any increases in body weight (1).
Again, these differences may be explained by higher doses and/or using CBD isolate, which may behave differently at cannabinoid receptors.
CBD may have a biphasic effect on appetite, which basically means it could both increase or reduce it. CBD does this by both blocking the CB1 receptor, and at the same time increases the chemical which activates CB1.
This effect is dose dependent, and is influenced by the presence of other cannabinoids in extracts – hence why full spectrum extracts behave differently to CBD alone (isolate).
Sedation & Sleepiness
In the same surveys, tiredness / sleepiness was reported in 2-12% of CBD users (1), (13). The same has been found from clinical research with CBD, where participants often mentioned that they felt a sense of drowsiness/sedation after taking 400mg doses of isolate (14), (15).
Problems with sleep and insomnia are amongst the most common reasons people take CBD, which may be due to its hypnotic and calming effects.
Cannabinoid receptor 1 (CB1) numbers in the brain vary based on what time of day it is (18), being higher at night than in the day. So, taking CBD in the day may have different effects than it does at night.
You could speculate that daytime CBD use may promote alterness, whereas nighttime use may promote sleep. Although, this is not the case for everyone and may depend on dose.
Feeling faint can be related to changes in blood pressure, just like after having blood drawn.
Dizziness is mostly related to the effect CBD has on blood pressure. In one clinical trial, CBD reduced blood pressure, as well as producing feelings of light headedness (19).
Its worth noting that in this study, standard medication for Parkinsons was taken alongside CBD which may have had a combined effect on dizziness.
CBD does interact with other medications, so its worth checking potential interactions with your doctor.
In another trial of healthy people, CBD also reduced blood pressure, but there were no reports of lightheadedness (20).
It might be the case that combining CBD with medications has a more dramatic effect on blood pressure and dizziness, although thats yet to be clarified.
In the survey, only 4% of CBD users reported feelings of dizziness (1). Its possible these 4% were also taking other medications, but thats purely speculative.
If you’ve ever smoked cannabis, then you’ll certainly know about cotton mouth. Sometimes using cannabis can make you feel like you’ve eaten balls of cotton wool, which unsurprisingly gives a dry sensation to your mouth.
A recent survey of over 2,000 regular CBD users reported that almost 12% of them experienced dry mouth (13). This was the most common side effect associated with CBD use. Another survey also reported dry mouth as the most common side effect, affecting 18% of users (1).
CBD has been associated with elevated liver transaminases (enzymes) (21). Transaminases are important for making proteins in the liver, which are used to make emergency energy and to rid waste from the body.
Elevations in transaminases (ALT and AST) usually indicate possible liver damage.
Elevations were also more common in people taking other drugs including valproic acid or clobazam (24).
Most changes in transaminases are mild and clinically insignificant, but when using other drugs the risk may become more significant. This is why its worth checking any interactions with your doctor.
Whilst CBD has been suggested to be a powerful anti-inflammatory (25), it also tells the immune system to chill out in a big way (26). For conditions which involve an overactive immune system, such as multiple sclerosis and IBD, CBD may be helpful (27), (28).
Telling the immune system to chill out on inflammation isn’t always a good thing though. When it comes to fighting infections, a little inflammation is protective. CBD may not be the best option in these cases.
Taking Vitamin C and immune stimulating mushrooms and herbs can help with weak immune systems.
Type of CBD: Full Spectrum Vs Isolate
The occurrence and magnitude of side effects depend on the type of CBD being used.
An analysis of multiple studies revealed that epilepsy patients using full spectrum CBD oil experienced far less side effects than those using CBD isolate (29).
76% of patients taking CBD isolate had mild side effects compared with only 33% using full spectrum CBD. 26% of patients taking CBD isolate had severe side effects compared with only 7% using full spectrum CBD.
71% of patients using full spectrum CBD also reported greater improvements in seizure frequency than those using CBD isolate, which was only 46%.
Not only did full spectrum users have better improvements, they used lower doses as well (270 – 390mg) compared to isolate users (1125 – 1625mg) (29).
Minimise The Risk of Side Effects
Stay well hydrated to avoid feelings of dizziness and to combat dry mouth
Ask your doctor about any potential drug interactions if you are taking other medication, before you try CBD. This may help reduce the risk of any changes to liver function.
Choose full spectrum CBD over CBD isolate, as side effects seem to be more common in those using CBD isolate.
Cycle CBD over periods of time. Having a regular break or washout from CBD may help keep the immune system balanced between TH1 and TH2 responses. This may ensure against excessive inflammation whilst also defending against infections.
Start with low doses and gradually increase to meet your individual needs for relief. Finding your own sweet spot may be preferable to going by doses you have seen elsewhere. Everyone is different, find what works for you.
Take a tolerance break every few months to ensure against over balancing your ECS.