CBD Side Effects and Risks: What the Research Shows

CBD side effects are well documented: after cannabidiol (CBD), the non-intoxicating compound of the hemp plant, studies most often report tiredness, diarrhoea and dry mouth, usually mild and linked to the amount. If you are looking up CBD oil side effects, CBD oil and CBD drops mean the same product here; hemp seed oil from the kitchen shelf is a different product. The real CBD risks sit elsewhere: with high amounts, with drug interactions, with certain groups and with product quality. This one page brings together side effects, the liver, addiction, drug interactions, antidepressants, contraindications, pregnancy and children, and for every statement we say whether it rests on human, animal or cell-culture research.

What Are the Side Effects of CBD?

The most commonly reported side effects of CBD are tiredness, diarrhoea and changes in appetite or weight. That was the finding of Iffland and Grotenhermen in 2017, in a review of clinical data and animal studies published in Cannabis and Cannabinoid Research [1]. Most of these side effects are mild and temporary, and they are reported more often at high amounts.

Dry mouth is mentioned often as well. Mild is not the same as harmless, though: how often and how strongly any negative effect of CBD shows up depends on the amount, the product and the person. In the research literature these adverse effects of CBD are filed as cannabidiol adverse effects, and the list is short and well studied in humans.

Forums are full of personal reports of bad effects of CBD, but they are not evidence: nobody knows which product was involved, and in clinical trials some complaints also turn up in the placebo group. We therefore rely on studies and name the evidence level each time.

The overview below sorts the most commonly reported side effects by how often they appear and how strong the evidence is.

Raised liver values are the one entry that is a risk rather than a nuisance, so the liver gets its own section below.

Does CBD Make You Tired?

Yes, CBD can make you tired: drowsiness is among the most common findings in clinical trials, as Iffland and Grotenhermen (2017) summarise [1]. Sleepiness becomes more likely at high amounts and together with alcohol or sedating medication, both of which are covered further down. In the studies, tiredness as a side effect is exactly that: an unwanted effect, not a product feature. For everyday life the road matters most. If you feel drowsy after CBD, do not drive or operate machinery until the feeling has gone.

Dry Mouth

Dry mouth after CBD is reported often, and it is a nuisance rather than a danger that usually passes on its own. Researchers suspect that cannabinoid receptors in the salivary glands could play a part in how much saliva is produced. That explanation comes mostly from animal studies; in humans the link has barely been examined. So if you notice a dry mouth, you are looking at a known and usually temporary side effect.

Diarrhoea and Stomach Upset

Diarrhoea is one of the most common findings in clinical trials with CBD, and it appears mainly at high amounts [1]. With CBD oil, a second possible trigger comes into play: the carrier oil. Carrier oils such as MCT oil from coconut can irritate digestion themselves and may cause bloating or loose stools, regardless of the cannabidiol. Stomach upset after CBD oil is therefore not always down to the CBD. If the complaints last, have them checked by a doctor.

Changes in Appetite and Weight

CBD does not reliably make you hungry, but studies report changes in appetite or weight in both directions: some participants ate more, others less [1]. A dependable “munchies” effect is not documented for CBD; the munchies are a THC effect, linked to tetrahydrocannabinol. Whether your appetite shifts after CBD varies from person to person. Treat a noticeable change in appetite or weight as a side effect worth watching, not as an outcome.

Does CBD Make Your Heart Race?

No, a racing heart is not a typical side effect of CBD, and if your pulse speeds up after a CBD product, check its THC content first. Research on whether CBD is bad for your heart is limited. What small human studies do suggest is that CBD may lower blood pressure slightly. That is why dizziness can follow, especially when you stand up quickly. Anyone who already has low blood pressure or takes blood pressure medication should talk to a doctor before using CBD; beta blockers are covered under drug interactions.

How Does CBD Make You Feel?

CBD does not make you feel high: unlike THC, cannabidiol is not intoxicating, and what people notice after CBD is mostly the side effects listed above.

Some study participants report restlessness, anxiety or mood swings, but those reports are rare and the evidence is weak. That CBD does not get you high is the short version; the full answer to does CBD make you high sits in a separate article. For brain development in children and teenagers, data are missing altogether, which is one reason the section on children below asks for particular caution. If you notice unfamiliar changes such as restlessness or trouble concentrating, take them seriously and speak to a doctor.

CBD Side Effects the Next Day and Over the Long Term

Short-term CBD side effects usually fade within hours to a day. After high amounts, drowsiness can still be noticeable the next morning, which is another reason not to drive while you feel it. The long-term effects of CBD are the least studied area: human data over months and years are limited and come mostly from medical trials at pharmaceutical doses, not from over-the-counter products. Whether tolerance builds up with long-term use has hardly been examined. We say that plainly, because few long-term studies do not mean proven harmless, and they do not mean proven harmful either.

Why CBD Affects People Differently

CBD affects people differently because the amount, the metabolism, other substances and the product itself decide whether side effects appear and how strong they are. The compound alone explains little: the same amount of cannabidiol can land very differently in two people.

Cannabidiol is broken down by the liver, mainly by enzymes of the cytochrome P450 family (CYP450). How quickly these liver enzymes work varies from person to person, and the same enzymes also process many medicines, which is where interactions come from. Alongside sits the endocannabinoid system, a signalling system of the body’s own that CBD may interact with; how exactly is only partly understood in humans.

In studies, the amount is the strongest factor: the higher it is, the more often side effects are reported. Products also differ in CBD content and purity, and individual factors such as body weight, existing conditions and medication add to the picture. What research has found about what CBD does in the body is explained in a separate article. Individual tolerance, in short, is the sum of several measurable factors rather than a mystery.

CBD Drug Interactions: What Drugs Should Not Be Taken With CBD?

CBD drug interactions are the most practically important risk of CBD, because cannabidiol can slow the breakdown of other medicines. It uses the same CYP450 liver enzymes, the same mechanism behind the grapefruit warning on many package leaflets, which is why CBD and grapefruit are often mentioned together [1]. A medicine can then stay in the body longer or at a higher level than intended.

CBD oil medication interactions matter most where a medicine has a narrow therapeutic range, so that small changes in its level count, as with CBD and blood thinners. The table lists the medicine classes where CBD interactions are discussed most, as a starting point for your conversation with a doctor or pharmacist, not as a CBD drug interactions list to work through on your own.

On CBD and aspirin, the concern is that both may affect bleeding, though the data are thin. CBD and paracetamol share the liver as their processing route, and whether that matters at everyday amounts is unsettled; neither is an all-clear. Anyone taking anti-inflammatory drugs, blood pressure medication or immunosuppressants should check with a doctor or pharmacist before using CBD.

CBD and Sleep Medication Such as Zopiclone

With CBD and zopiclone, the concern is added drowsiness plus a shared liver pathway. Zopiclone and similar sleeping pills, including benzodiazepines, are broken down partly via CYP450 enzymes, and CBD may slow that process. At the same time, drowsiness is one of CBD’s own most common side effects, so it could add to the sedative effect of the medicine. Ask the doctor who prescribed your sleep medication before you combine the two, and never change the sedative on your own.

CBD and Beta Blockers

With CBD and beta blockers, the question is blood pressure rather than a known dangerous interaction. Small studies suggest that CBD may lower blood pressure slightly, and beta blockers such as bisoprolol lower it too, so blood pressure may drop further when both meet. Dizziness, especially when standing up, is the most likely result. Do not change or pause your blood pressure medication on your own; talk to your doctor before adding CBD.

CBD and Lithium

CBD and lithium belong with the treating doctor, because lithium has a narrow therapeutic range and is monitored through regular blood levels. Case-level reports suggest that CBD could raise those levels, although the evidence is limited to individual cases and has not been tested in trials. Even a small shift can matter with lithium. Do not combine the two unless the doctor who monitors your lithium knows about it.

CBD Oil and Antidepressants

CBD oil and antidepressants should only be combined with medical advice, because CBD may change how some antidepressants are broken down. Several of them are processed by the same liver enzymes that CBD uses, and the data on what happens when the two meet are thin. That makes antidepressants the interaction question people search for most, and the one where an honest answer is mostly about who decides.

The two classes asked about most are SSRIs (selective serotonin reuptake inhibitors) and SNRIs (serotonin and noradrenaline reuptake inhibitors).

With CBD and SSRIs or SNRIs, the most likely added effect is drowsiness, because tiredness is one of CBD’s own common side effects. A changed breakdown in the liver could also mean the antidepressant stays in the body longer than intended. Whether that matters for you depends on the medicine, the amount and your own metabolism, which is why the prescribing doctor or a psychiatrist is the right person to ask. One rule holds without exception: never stop, reduce or replace an antidepressant because of CBD, and talk to the prescribing doctor before you combine CBD with antidepressants.

CBD and Cipralex (Escitalopram)

CBD and Cipralex should only be combined after talking to the prescribing doctor. Cipralex is the Swiss brand name of escitalopram, an SSRI. Escitalopram is broken down partly by the liver enzyme CYP2C19, and CBD may inhibit that enzyme, so the level of the antidepressant could rise. How much that matters in practice has not been studied in detail. Do not adjust your dose yourself; the prescribing doctor decides.

CBD and Venlafaxine

CBD and venlafaxine follow the same logic as the SSRIs: a possible interaction, thin evidence and a medical decision. Venlafaxine is an SNRI processed by liver enzymes including CYP2D6, which CBD may affect. Added drowsiness or dizziness is possible. Talk to your doctor first, and never change the dose because of CBD.

CBD Liver Damage: Is CBD Bad for Your Liver?

CBD can raise liver values, mainly at high amounts. In studies, raised levels of the liver enzyme ALT (alanine transaminase) showed up chiefly at pharmaceutical doses far above what cosmetic and aromatic products contain. That is not an all-clear for everyone: anyone with liver disease or on medication that strains the liver should talk to a doctor first.

The question of whether CBD is bad for your liver comes mainly from clinical data. Watkins and colleagues, writing in Clinical Pharmacology and Therapeutics in 2021, studied 16 healthy adults who received 1,500 mg of CBD a day under trial conditions for about three and a half weeks [2]. In 7 of the 16 participants, ALT rose above the normal range, and in 5 of them to more than five times the upper limit. This is a small, open-label phase I trial in humans: it shows a clear signal, but not how often this happens in the general population.

In practice, CBD liver damage is a real risk at the high doses studied, and the link between CBD and the liver depends strongly on the amount. Whether the much smaller amounts in cosmetic and aromatic products affect the liver cannot be answered from studies, because such amounts have hardly been examined. People with liver disease, including cirrhosis, and anyone with raised liver values should have CBD checked by a doctor before using it. For the kidneys there are no reliable data, so effects there can be neither confirmed nor ruled out.

The data on high doses suggest that the risk to the liver rises with the amount. Raised liver values at high amounts are the clearest finding on this whole page, and they are the reason the amount matters. What is known about very high amounts, and how much CBD is too much, is covered in a separate article.

Is CBD Addictive?

According to the World Health Organization (WHO), pure CBD shows no abuse or dependence potential. That was the conclusion of its Expert Committee on Drug Dependence in a 2018 critical review report, which assessed studies in humans and animals [3]. CBD addiction in the classic sense, with withdrawal and growing tolerance, is therefore not documented for pure CBD.

That finding applies to the compound, not to every product. If a product contains THC, that share brings its own dependence potential. If you smoke CBD flowers mixed with tobacco, you also take in nicotine, and there it is the tobacco that is addictive, not the CBD.

Tolerance to CBD has barely been studied. Whether the body gets used to regular amounts is simply not known, and we say so. Whether someone can manage without a product in daily life cannot be judged from studies alone anyway: if you find it hard to stop using a product, get help, for example from your GP or an addiction counselling service.

CBD Side Effects by Product Type

The product form changes which CBD side effects are likely, and the axis is contact with the body: from the skin, through digestion, to the airways. Cosmetics mostly stay on the skin; the side effects of CBD edibles and oil are the digestive complaints and drowsiness described above.

CBD gummies side effects follow the same pattern as those of oil, and a higher CBD percentage simply means more CBD in the same amount of oil, with side effects reported more often as the amount rises. Three look-alikes are worth separating: hemp seed oil is a cold-pressed food oil with practically no CBD; CBDA (cannabidiolic acid) is a different compound with far less research behind it; and synthetic CBD is not sold at uWeed.

Smoking CBD: Side Effects for the Lungs

When you smoke CBD, the smoke is the main risk, not the CBD. Any combustion of plant material produces tar and other harmful substances and irritates the airways, whether CBD flowers or tobacco are burning. Mixed with tobacco, nicotine and its own dependence potential come on top. So smoking CBD side effects come mostly from the smoking itself. With vaping, much depends on the e-liquid and the device: additives such as flavourings and thinners, and the quality of the hardware. In Switzerland, CBD vapes and e-liquids fall under the Tobacco Products Act. How vaping affects the airways over the long term has hardly been studied.

Product Quality as a Risk: THC Content and Lab Reports

Some of the side effects people report do not come from the CBD but from the product: too much THC, a mislabelled CBD content, or contamination with pesticides, heavy metals or solvent residues. That is why a lab report is not a detail but the proof that what is in the bottle matches the label.

In Switzerland, CBD products must contain under 1% THC; above that, they fall under the Narcotics Act. Even traces of THC below that limit can be noticeable in sensitive people and can lead to a positive drug test. When and under which conditions CBD is legal in Switzerland is explained in a separate article.

A certificate of analysis shows the CBD and THC content and ideally contaminants too. Check these five points on any lab report:

1. An independent laboratory is named.
2. The date and batch number match the product in your hand.
3. CBD content and THC content are given as measured values, with THC under 1%.
4. Contaminants such as heavy metals, pesticides and solvent residues have been tested.
5. The measured CBD content matches the figure on the label.

If the certificate is missing or does not match the batch, that is a good reason to ask the supplier.

CBD Contraindications: Who Should Avoid Taking CBD?

The main CBD contraindications concern pregnant and breastfeeding women, children and teenagers, people with liver disease, low blood pressure or a weakened immune system, and anyone on regular medication. For these groups, either data are missing or there are concrete reasons to hold back.

For liver disease, the reasons are set out in the liver section above. For low blood pressure, they are in the section on a racing heart. For regular medication, see drug interactions and antidepressants. People whose immune system is suppressed, whether by illness or by immunosuppressants, need particular caution because of possible interactions. Pregnancy, breastfeeding and children follow in the next two sections. The general rule for anyone wondering who should not take CBD: an existing condition or regular medication means asking a doctor or pharmacist before using CBD. In all these cases a medical assessment decides, not an online article.

CBD and Pregnancy: Is CBD Safe During Pregnancy and Breastfeeding?

Health authorities advise against using CBD while pregnant or breastfeeding, because the data needed to judge its safety for the unborn or breastfed child are missing.

There are hardly any human studies on CBD and pregnancy. What is known suggests that cannabinoids can cross the placenta and pass into breast milk, with much of that evidence coming from animal research. So the question of whether you can take CBD while pregnant has no reassuring answer: missing data here mean restraint, not an all-clear. The same applies to CBD and breastfeeding. Traces of THC in a product add a risk of their own. If you are pregnant or breastfeeding and are considering CBD, talk to your doctor or midwife first.

CBD for Kids: Is CBD Safe for Children?

Freely sold CBD products are not meant for children: they are made for adults, and uWeed sells only to people aged 18 and over. When it comes to CBD for kids, the key gap is brain development, where data on possible long-term effects in children and teenagers are missing.

Where CBD is used for children, it is as a prescription medicine and only under medical supervision. Over-the-counter CBD for children is therefore not a question an article can settle, and the answer to whether CBD is safe for kids is not one we can give either way. As a parent, raise the topic with your paediatrician, and keep CBD products out of children’s reach.

Common Misconceptions About CBD Side Effects

The most persistent misconceptions about CBD side effects either exaggerate the danger or play it down, and neither helps you separate myth from fact.

“Natural means harmless
A plant compound still has side effects and interactions, as the sections above show. Natural does not mean harmless.

“More is better”
In studies, the amount is the strongest risk factor for side effects. More is not better; it is more likely to cause complaints.

“Feeling worse first means it is working”
There is no evidence for a healing reaction with CBD. If you feel worse after CBD, that is a side effect, not progress, and it deserves to be taken seriously.

“CBD and THC are the same”
They are two different cannabinoids. THC is intoxicating and falls under the Narcotics Act from 1% upwards, CBD is not intoxicating. The difference between CBD and THC has its own article.

Frequently Asked Questions About CBD Side Effects

Is CBD Safe?

CBD is not free of risks. The common side effects such as tiredness, diarrhoea or dry mouth are usually mild, but the serious risks of CBD concern high amounts that can raise liver values, drug interactions, pregnancy, children and poor product quality. Whether CBD is bad for you therefore depends on the amount, the product and your situation. CBD dangers are real enough that anyone in a risk group should weigh the risks with a doctor first.

Can You Mix CBD and Alcohol?

Research on CBD and alcohol is thin, and what is known argues against combining them. Drowsiness can increase, because alcohol is sedating and tiredness is one of CBD’s most common side effects, and both are processed by the liver. Whether that matters at everyday amounts has hardly been studied in humans. After taking CBD together with alcohol, never drive, and the rules that apply on the road are explained in our article on CBD and driving.

The Bottom Line on CBD Risks

CBD side effects are known and mostly mild: tiredness, diarrhoea, dry mouth and changes in appetite top the list in studies. The real CBD risks lie with high amounts that can raise liver values, with drug interactions, with groups such as pregnant women and children, and with product quality, such as too much THC or a missing lab report. Knowing these points and asking a doctor first if you belong to a risk group is what an informed decision looks like. This article does not replace medical advice: with complaints, existing conditions or medication, your doctor or pharmacist is the right person to ask.

Sources on CBD Side Effects

1. Iffland K, Grotenhermen F (2017): An Update on Safety and Side Effects of Cannabidiol: A Review of Clinical Data and Relevant Animal Studies. Cannabis and Cannabinoid Research 2(1): 139–154.
2. Watkins PB, Church RJ, Li J, Knappertz V (2021): Cannabidiol and Abnormal Liver Chemistries in Healthy Adults: Results of a Phase I Clinical Trial. Clinical Pharmacology and Therapeutics 109(5): 1224–1231.
3. Cannabidiol (CBD): Critical Review Report, World Health Organization Expert Committee on Drug Dependence, 41st meeting, 2018, consulted on 4 November 2026.