CBD side effects do exist, but they are usually mild, infrequent, temporary and dose-dependent. CBD products are used for their potential relaxing and wellbeing properties. Even so, like any bioactive substance, it is worth knowing what effects it can cause, why they appear and how to avoid them.
In this guide we review, with up-to-date scientific references, what the side effects of CBD are, the interactions with medications, what is known about the liver and long-term safety, and how to reduce the risk. The golden rule: start with low doses, increase gradually and use CBD oil that is lab-tested.
Does CBD have side effects?
Yes, CBD can have side effects, although they are usually mild, infrequent, temporary and dose-dependent for the most part (1). It is also important to note that they can vary according to each person’s individual sensitivity.
Cannabidiol (CBD) is one of the main compounds of the hemp plant (Cannabis sativa). It is generally well tolerated: the World Health Organization (WHO) considers it safe and with no potential for abuse or dependence.
The most common side effects are drowsiness, dry mouth, dizziness, diarrhoea, appetite changes and a mild drop in blood pressure, almost always at high doses, and they tend to reverse when use is reduced or stopped.
Most of the adverse effects documented in the scientific literature come from clinical trials with very high pharmacological doses (up to 1,500 mg/day), far above the amounts present in over-the-counter hemp products (3, 7). At normal use doses, CBD’s safety profile is favourable.
Is CBD bad for you? Is smoking CBD bad?
No. CBD is not toxic and is not considered a substance of abuse. Unlike THC, it does not alter perception or reflexes and does not get you "high". The World Health Organization (WHO) concluded in its 2018 report that cannabidiol "does not appear to have abuse potential or cause harm" under the conditions evaluated (2).
When it is inhaled (CBD flowers, CBD hash or e-liquids), the main drawback is not the CBD itself, but combustion: inhaling smoke from any plant releases substances that irritate the airways.
Is CBD addictive?
No, CBD is not an addictive substance. Unlike THC, cannabidiol is not habit-forming and does not lead to physical or psychological dependence (2). Studies on continued CBD use have also documented no withdrawal syndrome or need to escalate the dose. More detail in does CBD cause addiction?.
Possible side effects of CBD
These are the side effects that most often appear when taking CBD, almost always mild and associated with high doses:
Drowsiness and fatigue
Because of its relaxing effect, some people notice drowsiness or tiredness, especially when starting out or at high doses. For some users this is a desired effect (rest and relaxation). More in CBD for sleep.
For other people, the drowsiness CBD can cause may interfere with daily activity. In several studies, fatigue has been associated with the use of CBD in combination with other medications (1). It is advisable to avoid risky tasks or driving until you know how it affects you. If you are concerned about driving, we cover it in driving and CBD: is it safe?.
Dry mouth
Dry mouth (cotton mouth) is a typical effect of THC, the psychoactive compound in marijuana, rather than CBD. In fact, cannabidiol does not reduce salivation and may even reverse THC’s effect on the salivary glands (7). CBD should therefore not produce the dry mouth associated with marijuana. However, it could be a side effect of CBD products that contain traces of THC, such as some Full Spectrum CBD oils, or from consuming edibles, CBD hash or CBD flowers.
Appetite changes
CBD can increase or decrease appetite depending on the person, through its interaction with the endocannabinoid system. Some studies point to an effect that reduces appetite (2) and others, conversely, that it stimulates it (3). In reality, more research is needed on whether CBD increases or decreases the feeling of hunger, although it has the potential to affect that system.
Dizziness
Dizziness is an occasional side effect of CBD (5). It may be related to a slight drop in blood pressure.
Drop in blood pressure
Cannabidiol can cause side effects related to a slight drop in blood pressure when given at high doses (4). Its potential benefit in people with hypertension is currently under investigation, but in healthy people it could cause dizziness or a feeling of faintness. We cover this in CBD and blood pressure.
If you experience any bothersome side effect, the advisable thing is to reduce or stop use and consult a professional.
Diarrhoea and digestive discomfort
In some cases, CBD can cause diarrhoea, although it is uncommon. It has mainly been linked to high doses, so its incidence rises with the dose (6). You may be interested in: how CBD affects the gut.
Why do CBD side effects appear?
CBD side effects are not random: they depend above all on several factors:
- The dose: most appear only at high doses, especially oral or sublingual (because absorption is higher than smoked or vaporised) and their intensity increases with the amount consumed.
- Individual sensitivity to CBD and other cannabis compounds: weight, metabolism and genetics mean each person responds differently.
- Product quality and interactions: a poorly labelled extract or use together with medications multiplies the risk.
- Individual circumstances: in people with liver disease, pregnancy, breastfeeding or who are minors, use is not recommended without professional supervision, as there is a possibility of unwanted side effects.
Can you overdose on CBD?
Not in the classic sense of poisoning: no serious CBD overdoses have been documented. What can happen is taking more CBD than your body tolerates well and noticing transient effects (drowsiness, dizziness, nausea). We cover this in CBD overdose: how much is too much?.
Side effects linked to CBD interactions with medications
More than the dose alone, the main risk factor of CBD is its interactions with medications. Cannabidiol is metabolised in the liver, in an enzyme complex called cytochrome P450 (CYP450). This system is the same one that processes a large part of commonly used drugs. By "competing" for those enzymes, CBD can increase or decrease the concentration of other medicines in the blood, or increase the toxicity of some medications (8).
Among the drug groups that may be affected are:
- Anticoagulants (e.g. warfarin)
- Antiepileptics (e.g. clobazam, valproic acid)
- Antidepressants (e.g. fluoxetine, sertraline)
- Benzodiazepines and other sedatives (e.g. diazepam, alprazolam)
- Immunosuppressants and certain cardiovascular drugs (e.g. tacrolimus, amiodarone, bisoprolol)
Combining CBD with sedatives or alcohol can increase side effects such as drowsiness, and combining it with hepatotoxic drugs (such as valproic acid) can add stress to the liver. If you take medication on a long-term basis, consult your doctor before using CBD. We explain it in detail in CBD and medications: what interactions are there?.
CBD side effects on the liver: how does it affect it?
CBD’s side effects on the liver are one of the most frequent doubts or concerns. In clinical trials with very high pharmacological doses (for example, 1,500 mg/day or 20 mg/kg/day, as in the drug Epidiolex), some participants showed elevations of liver transaminases (ALT/AST), a marker of liver stress. These elevations were mostly reversible when the dose was reduced or stopped, and occurred mainly in people who were taking other drugs at the same time (especially valproic acid).
A recent systematic review concluded that very high doses (>1,000 mg/day) are associated with a higher likelihood of liver enzyme elevation, while no liver damage was documented in adults at doses below 300 mg/day without concomitant medication — the range in which most over-the-counter CBD users sit.
This does not mean CBD harms the liver in healthy people, but that people with pre-existing liver disease, or who take medication, should take extra precautions and consult their doctor. More information in how does CBD affect the liver?.
CBD contraindications: who should not take it?
Like any substance, CBD has situations where its use is not advised without professional supervision:
- Pregnancy and breastfeeding: not advised due to the lack of safety data (CBD and pregnancy).
- Children and adolescents: only on professional advice.
- People with liver disease: require medical monitoring.
- People taking long-term medication: because of interactions via CYP450 in the liver.
- Heart conditions: CBD can slightly influence blood pressure and heart rate.
We have dedicated a complete guide to this topic: what contraindications does CBD have?.
Product quality: the real risk of side effects
Many of the adverse effects attributed to CBD do not come from cannabidiol, but from poor-quality products. An analysis published in the scientific journal JAMA evaluated dozens of CBD products sold online and found that only 31% were correctly labelled; in addition, 21% contained undeclared THC. Other studies have detected pesticides, heavy metals or solvents in low-quality extracts.
Put another way: a large part of the side effects attributed to the use of CBD products could actually be reactions to contaminants, miscalculated doses or hidden THC. That is why traceability is decisive.
A specific and especially worrying risk is adulteration with synthetic cannabinoids. Some CBD products, such as buds and vaping liquids, are sprayed or mixed with synthetic cannabinoids (such as HHC, THCP or other analogues) to mimic potency cheaply. Unlike natural cannabidiol, these substances have little-known, unpredictable and potentially dangerous effects, and are behind many adverse reactions mistakenly attributed to CBD.
At Cannactiva, every batch undergoes independent laboratory analysis that verifies the real CBD content and compliance with the legal THC limit. In addition, we have never sold products with synthetic cannabinoids of any kind. We believe the best option is to use CBD flowers, CBD hash and CBD oil obtained from clean sources, pesticide-free cultivation and certified quality.
How to minimise CBD side effects
Most side effects are avoided with three simple habits:
- Start with low doses and increase gradually ("start low, go slow"). Watch how your body reacts over a few days before increasing. To get started, a 5% CBD oil lets you adjust drop by drop; check our CBD dosage guide.
- Choose products with laboratory analysis and clear labelling in milligrams. Avoid dubious sources: quality is what most influences tolerance.
- Consult your doctor if you take medication, have a diagnosed condition or are pregnant. And avoid combining CBD with alcohol or sedatives.
If drowsiness, dizziness or discomfort appears, it is usually enough to reduce the dose at the next intakes.
Long-term toxicity and safety of CBD
Is CBD safe?
To date no case of serious toxicity has been documented associated with the use of cannabidiol at normal doses. Studies show that CBD is a relatively safe substance, although more research is needed to fully understand its long-term safety.
Can you take CBD for life?
There is no evidence to suggest that CBD is dangerous with prolonged use, but there is still no specific research on continued use over years. A review on toxicity concluded that normal use doses do not represent a risk for daily consumption, provided there are no contraindications (8). If you plan to use it long-term for health reasons, it is advisable to do so with professional monitoring.
Frequently asked questions about CBD side effects
How many mg of CBD a day are safe?
There is no established universal dose. One recommendation is to start with 10 mg a day and adjust according to your response and weight. More information in CBD dosage.
Are CBD side effects serious or long-lasting?
No. When they appear, they are mild, transient and reversible: they usually disappear within a few hours when the dose is reduced or stopped. No serious side effects or dependence have been documented at normal use doses.
Does CBD show up on a drug test?
Pure CBD is not detected in tests, which look for THC. The risk appears with Full Spectrum or poor-quality products that contain traces of THC above what is declared. We explain it in driving and CBD.
In summary
CBD has a favourable safety profile: its side effects are infrequent, mild and reversible, and it does not cause addiction. The important precautions are interactions with medications, people with liver disease or who are pregnant, and above all product quality.
At Cannactiva we remind you that CBD products are not medicines or food supplements and are intended for external use: this information is educational and does not replace the advice of a healthcare professional.
This is an informational article that does not aim to diagnose, prevent or treat any disease or symptom; its content may complement, but never replace, professional diagnosis or treatment. In most European countries CBD is not regulated for oral use: Cannactiva products are intended for external use. Consult a professional before using CBD.
References
- Huestis, M. A., et al. (2019). Cannabidiol Adverse Effects and Toxicity. Current Neuropharmacology, 17(10), 974–989.
- World Health Organization (2018). Cannabidiol (CBD) Critical Review Report.
- Pinto, J. S., & Martel, F. (2022). Effects of Cannabidiol on Appetite and Body Weight: A Systematic Review. Clinical Drug Investigation, 42(11), 909–919.
- Jadoon, K. A., et al. (2017). A single dose of cannabidiol reduces blood pressure in healthy volunteers. JCI Insight, 2(12), e93760.
- Hundal, H., et al. (2018). The effects of cannabidiol on persecutory ideation and anxiety. Journal of Psychopharmacology, 32(3), 276–282.
- Szaflarski, J. P., et al. (2018). Long-term safety and treatment effects of cannabidiol. Epilepsia, 59(8), 1540–1548.
- Andreis, K., et al. (2022). Cannabinoid CB1 receptors regulate salivation. Scientific Reports, 12(1), 14182.
- Henderson, R. G., et al. (2023). Cannabidiol safety considerations: acceptable daily intake and upper intake limits. Regulatory Toxicology and Pharmacology.
- Brown, J. D., & Winterstein, A. G. (2019). Potential Adverse Drug Events and Drug-Drug Interactions with CBD. Journal of Clinical Medicine, 8(7), 989.
- Watkins, P. B., et al. (2021). Cannabidiol and Abnormal Liver Chemistries in Healthy Adults. Clinical Pharmacology & Therapeutics, 109(5), 1224–1231.
- Lo, L. A., et al. (2023). Cannabidiol-associated hepatotoxicity: A systematic review and meta-analysis. Journal of Internal Medicine, 293(6), 724–752.
- Bonn-Miller, M. O., et al. (2017). Labeling Accuracy of Cannabidiol Extracts Sold Online. JAMA, 318(17), 1708–1709.
- Iffland, K., & Grotenhermen, F. (2017). An Update on Safety and Side Effects of Cannabidiol. Cannabis and Cannabinoid Research, 2(1), 139–154.
