Cannabidiol (CBD) has become very popular as a natural option for problems like chronic pain, anxiety, and seizures. Many people praise its possible benefits, and it is often described as well-tolerated. Still, CBD is an active substance, and it can cause side effects. These side effects can be mild or, in some cases, more serious, especially when CBD is taken with other medicines or by people with existing health problems. This article gives a detailed CBD side effects list by body system, explains what can change your risk, and outlines important drug interactions so you can use CBD more safely.
Research on CBD is growing quickly. There is strong evidence for some uses, such as epilepsy, where prescription CBD oil (Epidiolex) is an FDA-approved seizure medicine. For many other uses, proof is still limited and ongoing. Another problem is that most non-prescription CBD products are not tightly regulated, so their strength, purity, and possible contaminants can vary a lot. Knowing the potential side effects and interactions is very important for anyone thinking about adding CBD to their health routine.
What Are the Potential Side Effects of CBD?
CBD is often praised because it does not cause a “high” like THC and usually has a better safety profile. But it can still cause unwanted reactions. The side effects of CBD can differ widely from person to person. Dose, personal sensitivity, and other medicines all play a role. Knowing these possible reactions is an important step in using CBD wisely.
Most Common CBD Side Effects
People who report side effects from CBD often notice a small set of common, usually mild problems. These include:
- Drowsiness and fatigue – feeling sleepy or unusually tired, especially at higher doses or when combined with other sedating substances.
- Dry mouth – often called “cottonmouth,” caused by less saliva.
- Digestive issues – diarrhea and reduced appetite are often mentioned.
These effects are often manageable and may fade with a lower dose or stopping CBD.
Clinical studies on CBD for epilepsy regularly list somnolence (drowsiness) and fatigue among the most common side effects. Surveys of parents giving CBD to children with uncontrolled epilepsy show the same pattern. These side effects are usually mild, but they can still affect daily activities and should not be ignored.
Less Common CBD Side Effects
Some side effects are reported less often but still matter:
- Lightheadedness or dizziness, sometimes linked to blood pressure changes.
- Weight changes (gain or loss).
- Nausea and vomiting (less common than diarrhea or low appetite).
- Mood changes, such as irritability or agitation, especially with prescription CBD in epilepsy.
In some studies, blood tests showed elevated liver enzymes without clear symptoms, which can mean the liver is under stress. This is one reason medical supervision is important, especially for people with existing health issues or those taking other medicines.
Serious or Rare Adverse Reactions
Serious side effects from CBD are rare but do occur, mostly with high doses or medical products like Epidiolex:
- Liver injury – reported at high doses and more likely when taken with other liver-stressing drugs. Symptoms can include upper stomach pain, dark urine, or yellowing of the skin or eyes. These need urgent medical care.
- Severe seizure-related events – in some epilepsy studies, events like convulsions and status epilepticus were reported, although it is hard to say how much CBD alone contributed.
- Allergic reactions – rashes, swelling (angioedema), or other allergy signs have been reported.
- Male reproductive effects in animals – such as smaller testes and lower sperm production. We do not yet know how this applies to humans, but it raises concern, particularly for men.
These rare but serious reactions show why medical advice is important, especially at high doses or with unregulated products.
Detailed CBD Side Effects List by Body System
To better see how CBD can affect the body, it helps to group reported side effects by body system.
Neurological Effects
CBD acts on the brain and nervous system, so many side effects involve this area.
Drowsiness and Sedation
Drowsiness is one of the most frequent neurological side effects. People may feel sleepy, sluggish, or heavily sedated. In trials for Dravet and Lennox-Gastaut syndromes, somnolence was common and often linked to higher doses.
This effect can be much stronger if CBD is taken with other central nervous system depressants such as:
- Alcohol
- Benzodiazepines (e.g., Xanax, Ativan)
- Some antihistamines
Anyone who feels sleepy after CBD should be careful with driving or using machines. Some people use CBD because they want this calming effect for sleep, but for others it can interfere with work, school, or daily tasks.
Dizziness and Impaired Coordination
Some users feel dizzy or lightheaded after taking CBD. This may be tied to short-term drops in blood pressure. Coordination may also be affected, making balance or fine movements harder.
Dizziness is more likely:
- When you first start CBD
- When you quickly raise the dose
- When CBD is combined with other drugs that cause dizziness
Older adults and people with balance problems should be especially careful due to a higher risk of falls.
Gastrointestinal Effects
The digestive system is often affected, especially when CBD is taken by mouth.
Diarrhea and Nausea
Common digestive side effects include:
- Diarrhea
- Nausea or upset stomach
- Vomiting (less common)
These may be due to CBD itself or the carrier oil (like MCT or sesame oil) in the product. While usually mild, ongoing diarrhea can lead to dehydration and loss of minerals. If symptoms are severe or do not go away, you should speak with a healthcare professional.
Changes in Appetite or Weight
CBD can affect appetite:
- Reduced appetite – more common; can lead to weight loss over time.
- Increased appetite – less often reported; may cause weight gain.
In studies on children with epilepsy, decreased appetite was a frequent side effect. These changes likely relate to CBD’s action on the endocannabinoid system, which helps control hunger and metabolism. People with weight or nutrition issues should monitor changes closely and seek advice if they notice big shifts.
Liver and Metabolism Effects
The liver is heavily involved in processing CBD, which is why liver-related side effects matter, especially at higher doses.
Elevated Liver Enzymes
Studies with Epidiolex show that CBD can raise liver enzymes such as AST and ALT. This suggests stress or damage to liver cells. In many cases this is mild and causes no symptoms, but larger increases can signal more serious problems.
The chance of liver enzyme rises goes up with higher doses and when CBD is used with other liver-acting drugs, especially valproate (an anti-seizure drug). Regular blood tests are often used to check liver function in these situations.
Potential Hepatotoxicity at High Doses
At high doses, CBD can, in rare cases, cause clear liver injury. Symptoms can include:
- Yellowing of the skin or eyes
- Persistent nausea or vomiting
- Upper abdominal pain
- Dark urine or pale stools
The FDA review of Epidiolex lists liver injury as a safety concern, but also notes that it can be managed with monitoring and dose changes. With non-prescription CBD and no monitoring, damage could go unnoticed. Animal studies show liver cell injury at very high doses, likely linked to how CBD is broken down by liver enzymes (cytochrome P450). People with liver disease may be more at risk and may need lower doses or to avoid CBD.
Cardiovascular Effects
CBD can also affect the heart and blood vessels.
Blood Pressure Changes
CBD may lower blood pressure in some people. In one study of healthy men, a 600 mg dose of CBD led to short-term drops in blood pressure. People with low blood pressure or those taking blood pressure medicines may feel:
- Dizziness
- Faintness
- Lightheadedness on standing
Animal studies at very high doses have shown more serious effects like strong drops in blood pressure, slow heart rate, and even heart failure, but these doses are far above usual human doses. People with heart disease or blood pressure issues should talk with a doctor before using CBD.
Psychological Effects
Because CBD acts on the brain, it can also affect mood and mental state.
Mood Changes or Anxiety
Many people use CBD hoping it will reduce anxiety. Some research supports this at certain doses. But some users report the opposite: more anxiety, irritability, or agitation. In clinical data for Epidiolex, problems like agitation, depression, aggression, and panic attacks appear, similar to other anti-seizure drugs.
Some studies suggest CBD may follow an “inverted U-shaped” curve for anxiety relief: low to moderate doses may help, but higher doses may do nothing or even make anxiety worse. If mood gets clearly worse after starting CBD, you should stop taking it and seek medical advice.
Other Potential Side Effects
Dry Mouth
Dry mouth is very common with CBD. It is caused by reduced saliva, likely due to CBD’s action on receptors in the salivary glands. It is usually harmless but can be annoying. Drinking water often and chewing sugar-free gum may help.
Rashes or Allergic Reactions
Some people develop skin reactions or allergies to CBD products or their ingredients. These may include:
- Rash
- Itching
- Hives
- Swelling of the face, lips, tongue, or throat (angioedema)
Severe swelling or trouble breathing is a medical emergency. Allergies can be to CBD itself or to carrier oils, flavorings, or other additives. For example, in one trial a person had to stop due to allergy to the sesame oil used in the product. Always check ingredient lists and stop use if you notice signs of allergy.
Factors Impacting CBD Side Effects
Not everyone reacts to CBD in the same way. Several key factors influence who gets side effects and how strong they are.
CBD Dosage and Delivery Method
Dose is one of the biggest factors. Higher doses bring a higher chance and stronger side effects. In epilepsy studies with Epidiolex, higher doses clearly linked to more drowsiness, diarrhea, and raised liver enzymes. A common guideline is “start low, go slow”: begin with a small dose and raise it gradually while watching how you feel.
The method you use also matters:
| Method | Onset | Side effect pattern |
|---|---|---|
| Inhaled (vaping, smoking) | Fast (minutes) | Higher peak levels; more chance of sudden side effects |
| Oral (oils, capsules, edibles) | Slower (30-120 min) | Longer-lasting; side effects may build up over time |
| Topical (creams, balms) | Local effect | Low risk of body-wide side effects; possible local skin reactions |
Individual Sensitivities and Medical Conditions
Each person’s biology is different. Genes, metabolism, other illnesses, and habits like alcohol use all change how CBD works and how long it stays in the body.
Groups that may be more sensitive include:
- People with liver disease (slower CBD breakdown and higher levels)
- People with depression, anxiety disorders, or substance use history
- Those on many medicines at once
Special care is needed for:
- Children and teens – developing brains and bodies.
- Pregnant or breastfeeding women – possible risk to the fetus or baby.
- Older adults – age-related changes in liver, kidney, and heart function.
These groups should only use CBD with medical guidance, if at all.
Product Quality and Contaminants
Most CBD products sold over the counter are not checked by the FDA before sale. Problems often found in studies include:
- Wrong CBD amounts (too much or too little compared with the label)
- Unexpected THC, even in products labeled “THC-free”
- Contaminants like pesticides, heavy metals, or leftover solvents
These issues can cause extra side effects or even THC intoxication. To lower risk, choose products that:
- Come from well-known brands
- Provide recent third-party lab reports (Certificates of Analysis)
- Show exact levels of CBD, THC, and test results for contaminants
CBD Drug Interactions: What to Know
One major safety issue with CBD is its effect on other medicines. CBD can change how drugs are broken down in the body, which can raise or lower drug levels and lead to reduced effect or more side effects.
Medications Changed by the Liver
Many drugs are processed by liver enzymes known as cytochrome P450 (CYP). CBD uses and affects these enzymes. When CBD slows an enzyme, levels of other drugs that use that enzyme can rise. When it speeds an enzyme, levels can fall.
This can affect:
- Prescription drugs
- Over-the-counter medicines
- Herbal supplements
Changes in drug levels can cause anything from loss of benefit to dangerous side effects, depending on the drug.
Cytochrome P450 Interactions
CBD is mainly broken down by CYP2C19 and CYP3A4. It can also block enzymes like CYP1A2, CYP2B6, CYP2C8, CYP2C9, and some UGT enzymes. Many drugs rely on these same enzymes.
Examples:
- Rifampicin (a CYP3A4 inducer) can lower CBD levels in the blood.
- Ketoconazole (a CYP3A4 inhibitor) can nearly double CBD levels.
This shows how complex these interactions can be and why professional advice is important when mixing CBD with other drugs.
Drugs With Notable Interactions
Anticoagulants (e.g., Warfarin)
CBD can raise blood levels of warfarin and other blood thinners, increasing the risk of serious bleeding. Anyone on warfarin or similar drugs should speak with a doctor before using CBD. Blood clotting tests and dose changes may be required.
Antiepileptics (e.g., Clobazam, Valproate)
CBD can raise blood levels of several anti-seizure drugs, including clobazam and its active breakdown product, as well as valproate. This can lead to:
- Extra sedation
- Higher risk of liver injury (especially with valproate)
- Other drug-specific side effects
In trials, people taking both CBD and valproate showed more liver enzyme elevations. Blood tests to check drug levels and liver function are often needed.
Sedatives and CNS Depressants
CBD taken with sedatives or other central nervous system depressants can strongly increase drowsiness. This includes:
- Benzodiazepines (e.g., alprazolam, lorazepam)
- Antipsychotics
- Some antidepressants
- Over-the-counter antihistamines (e.g., diphenhydramine)
- Alcohol
The mix can lead to very slow reaction times, poor coordination, and higher risk of falls or car accidents. Use together only under medical supervision.
Risks of Doubling Up on Side Effects
Even when CBD does not directly change drug levels, it can still add to side effects from other medicines. Many drugs share side effects with CBD, such as:
- Drowsiness
- Dizziness
- Diarrhea or stomach upset
For example:
- CBD + a sedating antidepressant → extra sleepiness and tiredness.
- CBD + metformin or certain acid-reducing drugs → worse diarrhea.
This can make people feel unwell enough to stop important medicines. Going over all your medicines and supplements with a healthcare provider before starting CBD is very important.
Who Should Take Special Precautions with CBD?
Some groups face higher risks from CBD side effects or interactions and should be especially careful.
Children and Adolescents
Children and teenagers may respond differently to CBD than adults. Epidiolex is approved for certain severe seizure disorders in children as young as one year, but this use is tightly controlled, with liver tests and close monitoring.
For non-prescription CBD, we have very little safety data in this age group. Animal research raises concerns about effects on brain development and male fertility. Unless prescribed by a specialist, CBD use in children and teens is best avoided.
Pregnant or Breastfeeding Women
There is not enough human research to say CBD is safe during pregnancy or breastfeeding. Animal studies raise several red flags, including:
- More embryo-fetal deaths
- Lower fetal body weights
- Problems with male reproductive organ development and later fertility
On top of this, unregulated products may contain other substances harmful to the baby. Pregnant and breastfeeding women are usually advised to avoid CBD completely.
Older Adults
Older adults often have changes in liver, kidney, and heart function that affect how drugs are processed. They also tend to take more medicines, which raises the chance of interactions.
CBD could interact with:
- Blood thinners
- Heart medicines
- Sedatives and sleep aids
Although trials of Epidiolex did not find special problems unique to older adults, dose changes and close monitoring are often needed. Older adults should always talk to a healthcare provider before starting CBD.
People with Liver or Kidney Disorders
Those with liver disease process CBD more slowly, which can raise CBD levels and side effects, including added liver damage. High-dose CBD is already linked with liver enzyme increases and sometimes clear liver injury, so this risk is higher in people whose liver is already weakened.
Kidney problems can also interfere with clearing CBD breakdown products. People with moderate to severe liver or kidney disease should only use CBD under direct medical care, if at all, with regular blood tests.
How to Minimize CBD Side Effects
Many people can reduce CBD side effects by using it carefully and making informed choices.
Tips for Safer CBD Use
To lower your risk of side effects:
- Start low, go slow – Begin with the smallest possible dose and increase gradually while watching how you feel. This helps you find the lowest dose that works for you.
- Choose quality products – Use CBD from brands that offer third-party lab tests showing:
- Exact CBD and THC levels
- Tests for pesticides, heavy metals, and solvents
- Think about the form – Inhaled CBD acts fast and can cause sudden effects; oral forms act slower but last longer; topicals usually have fewer body-wide effects.
- Avoid risky mixes – Be careful combining CBD with alcohol, sedatives, blood thinners, and other high-risk drugs unless your doctor approves.
When to See a Doctor
You should talk with a doctor before starting CBD if you:
- Have chronic health problems
- Are pregnant or breastfeeding
- Take prescription or over-the-counter medicines regularly
Seek medical help right away if you notice:
- Upper stomach pain, dark urine, pale stools, or yellow eyes/skin
- Serious allergic reactions (swelling of face or throat, trouble breathing, widespread rash)
- Strong mood changes such as severe agitation, depression, or panic
- Severe or ongoing diarrhea, vomiting, or dehydration
- Clear worsening of an existing condition after starting CBD
Your doctor can help decide if CBD is the cause and adjust your dose or suggest other options.
Frequently Asked Questions about CBD Side Effects
Can CBD Make You Fail a Drug Test?
Most drug tests look for THC, not CBD. Pure CBD should not cause a positive test. However, many products contain trace THC, especially full-spectrum products (up to 0.3% THC by law for hemp-derived products). Regular use of these, especially at high doses, could build up enough THC metabolites to trigger a positive result.
CBD isolate products, which are nearly pure CBD with no THC, carry a much lower risk. Broad-spectrum products remove THC but keep other cannabinoids. Because some products are mislabeled or contaminated, anyone who faces drug testing should either use a high-quality CBD isolate with strong lab proof or avoid CBD entirely to remove the risk.
Is It Safe to Use CBD Daily?
Many people take CBD every day and tolerate it well at moderate doses. Clinical studies often involve daily use over weeks or months. But long-term safety over many years is still not fully known.
Daily use can increase the chance of:
- Ongoing drowsiness or fatigue
- Chronic digestive issues
- Long-term liver enzyme elevation, especially with higher doses or certain drugs
Some people may also develop tolerance and need higher doses for the same effect. Regular check-ins with a healthcare provider are a good idea for anyone using CBD daily, especially if they take other medicines.
How Long Do Side Effects Last?
The length of CBD side effects depends on dose, method of use, your metabolism, and the type of side effect. For oral CBD, mild effects like drowsiness, dry mouth, or lightheadedness often last a few hours. Inhaled CBD tends to act and wear off faster.
If side effects come from a dose that is too high, lowering the dose or stopping CBD usually helps within a day or two as the substance leaves your body. Liver-related issues or drug interactions may last longer and need tests and treatment. Any side effect that is strong, long-lasting, or worrying should be checked by a healthcare professional.
Key Takeaways for Safe CBD Use
CBD shows real promise, especially for seizure disorders, but it is still a drug with both benefits and risks. It should not be viewed as harmless just because it is plant-based or sold over the counter.
Main points to remember:
- Common side effects include drowsiness, dry mouth, diarrhea, and appetite changes.
- More serious risks like liver injury and strong drug interactions exist, especially at higher doses.
- Dose, method of use, personal health, and product quality all shape your risk.
- Certain groups-children, pregnant or breastfeeding women, older adults, and people with liver or kidney problems-need special care.
- CBD can interact with many medicines processed by liver enzymes, including blood thinners and anti-seizure drugs.
Use CBD with the same care you would give to any other medication: choose reliable products, start with small doses, and be honest with your healthcare provider about everything you take. As research continues, we will learn more about long-term effects and safe use. For now, a careful, informed approach is the best way to lower risk and get the most benefit if you decide to use CBD.