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CBD Oil Side Effects: What You Need to Know
By Todd Smith, Co-Founder of Joy Organics
CBD oil has a strong safety profile relative to most supplements and medications — the World Health Organization's 2018 review concluded it is "generally well tolerated with a good safety profile." [1] But side effects do occur, and the drug interaction potential is clinically meaningful for people on prescription medications. Here's an accurate, complete picture.
Common Side Effects
Drowsiness and Fatigue
The most commonly reported side effect. Serving-dependent — more common at higher servings (50mg+). At lower daily amounts (15–25mg), drowsiness is less common and some people find CBD mildly alerting.
Management: If you experience drowsiness, take CBD in the evening or reduce your serving size.
Digestive Changes
- Dry mouth (inhibition of saliva secretion via CB receptors in salivary glands)
- Mild nausea (more common in new users; usually resolves in the first week or two)
- Diarrhea or loose stools (more common with higher amounts or MCT-oil based products)
- Changes in appetite (CBD can both increase and decrease appetite in different people)
Management: Take with food; reduce amount if GI effects persist.
Transient Blood Pressure Changes
Some research has found high CBD amounts may cause a brief, transient drop in blood pressure. This is most relevant for people on antihypertensive medications or those with low blood pressure.
Mood or Energy Changes
Some people report feeling more settled and calm; a smaller number report mild mood changes, including irritability and agitation, when starting CBD. These are typically mild and temporary as the body adjusts. CBD affects the endocannabinoid system and cannabinoid receptors, which may contribute to these mood or energy changes.
Drug Interactions: The Most Important Safety Consideration
CBD is metabolized primarily by CYP3A4 and CYP2D6 liver enzymes — the same enzymes that process many common medications. When CBD inhibits these enzymes, it can alter how medications are metabolized, potentially increasing or decreasing their effects. Food can also change how your body absorbs CBD, which may influence these interactions.
Medications with significant interaction potential:
- Blood thinners (warfarin): CBD may increase warfarin effect; monitoring recommended.
- Antiepileptic drugs: CBD can affect levels of some seizure medications (this is a known interaction from Epidiolex clinical trials, which is an FDA approved cannabis derived compound).
- Antidepressants (SSRIs, SNRIs): Share CYP2D6 metabolism; potential for altered levels when combined with other drugs or other medications.
- Sleep medications (zolpidem, benzodiazepines): Additive sedation via CYP3A4, especially when used with alcohol or other sedating substances.
- Immunosuppressants (tacrolimus, cyclosporine): CYP3A4 interactions that may require dose adjustments alongside other supplements or other drugs.
- Statins: Some statins are metabolized by CYP3A4, which can be influenced by CBD and other ingredients in hemp-derived products.
The "grapefruit test": If your medication carries a warning against consuming grapefruit, CBD may produce similar interactions — both inhibit CYP3A4.
If you take any prescription medication or are using other medicines, consult your healthcare professional or doctor before starting CBD oil or other hemp-derived CBD product, especially considering the potential side effects and drug interactions involving the cytochrome P450 system. This is not a formality.
Who Should Exercise Particular Caution
People taking multiple prescription medications. Interaction risk compounds with more medications.
Pregnant and breastfeeding individuals. Pregnant and breastfeeding individuals are advised to avoid CBD products by the FDA, due to unknown effects on breast milk and fetal development. Evidence on fetal/infant safety is insufficient, and further research is needed to understand the potential side effects in these populations.
People with liver disease. High-serving CBD has been associated with elevated liver enzymes in some research (primarily in pharmaceutical Epidiolex trials, an FDA-approved cannabis derived compound for certain types of epilepsy). Normal consumer amounts in healthy adults are unlikely to cause liver problems, but pre-existing liver conditions warrant medical supervision.
People over 65. Slower metabolism means CBD stays active longer and at higher concentrations; lower starting amounts are recommended.
Children and adolescents. Not adequately studied for safety outside of specific medical contexts (Epidiolex is prescribed for pediatric epilepsy under medical supervision, including severe forms such as Lennox-Gastaut syndrome and Dravet syndrome).
What's NOT a Side Effect of CBD Oil
Addiction or physical dependence. CBD is not addictive. The World Health Organization (WHO) and other agencies in complementary and integrative health have found no potential for abuse or dependence. Stopping CBD does not cause withdrawal.
Intoxication. CBD does not produce a high at any amount. Full spectrum CBD oils derived from the hemp plant contain trace THC (under 0.3%) that is too low to cause psychoactive effects or intoxication.
Fatal overdose. There is no established lethal dose of CBD in humans, including from nonprescription CBD products. The safety margin is extremely high.
Permanent or irreversible effects. Side effects from consumer amounts of CBD are reversible and resolve with serving reduction or discontinuation. More research is needed to fully understand potential side effects and interactions with other controlled substances and regulated medications.
Frequently Asked Questions
What are the negative side effects of CBD oil?
The most common: drowsiness (especially at higher amounts), dry mouth, digestive changes including diarrhea or nausea, and drug interactions via CYP450 liver enzymes. Most healthy adults tolerate consumer CBD amounts well, but possible side effects may increase with higher servings. CBD derived from the cannabis sativa plant, specifically hemp under the 2018 Farm Bill, is generally considered safe when sourced from a reputable source free of heavy metals and contaminants.
Is CBD oil safe to take every day?
For most healthy adults not on interacting medications, daily CBD use appears safe based on available evidence. Long-term (years) safety data is still developing, but there are no established concerns at consumer amounts for healthy individuals.
Does CBD oil cause liver damage?
Very high pharmaceutical servings have been associated with liver enzyme elevation in Epidiolex trials. At typical consumer amounts (15–100mg/day) in healthy people, liver effects are not a documented concern. People with existing liver conditions should consult a doctor.
Can CBD oil make anxiety worse?
We can't make claims about anxiety specifically. Some people report feeling more unsettled when starting CBD — this is usually temporary. CBD's pharmacology (serotonin system, ECS modulation) is associated with calming effects, but individual responses vary.
Does CBD oil interact with any medications?
Yes, potentially significantly. CBD inhibits CYP3A4 and CYP2D6 liver enzymes that process many common medications. If you take prescription medication, consult your healthcare provider before using CBD.
The Bottom Line
CBD oil's side effect profile is favorable for most healthy adults. The primary practical concerns are serving-dependent drowsiness, digestive effects, and — most importantly — drug interactions via CYP450 enzymes. If you take prescription medication, CYP450 interactions are the most clinically relevant consideration and warrant a conversation with your healthcare provider before starting CBD.
These statements have not been evaluated by the Food and Drug Administration. These products are not intended to diagnose, treat, cure, or prevent any disease. Consult a healthcare provider before adding any new supplement to your routine, especially if you take prescription medications.
Sources
- World Health Organization. "Cannabidiol (CBD) Critical Review Report." 2018.
- Iffland K, Grotenhermen F. "An Update on Safety and Side Effects of Cannabidiol." Cannabis and Cannabinoid Research. 2017;2(1):139–154. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5569602/
