Cannabidiol (CBD) is the non-psychoactive compound in cannabis, known for its numerous health benefits and ability to act as a food supplement.

Recently, it’s made headlines as a potential treatment for patients suffering with Dravet Syndrome; a rare form of epilepsy that can cause more than 30 seizures a day.

Because of the stigma surrounding cannabis, it’s been difficult for medical professionals to compile a full list of medically approved potential side effects for CBD. This means research on the long term side effects of CBD is largely hindered by the lack of human participants in trials, as well as funding.

There have been some side effects reported by users of CBD, which we would like to cover in this post. It’s important to note that CBD is a natural substance that poses no inherent danger to humans. Side effects occur simply as a result of introducing a new substance into the body, and do not necessarily have to be negative.


Cannabidiol is generally considered safe when it is taken orally by adults.

Studies have deemed 300mg of CBD per day safe for use for 6 months. A review paper on the ‘safety and side effects of cannabidiol’ by the NBCI reports that “high doses [of] up to 1,500 mg/day of CBD are reportedly well tolerated in humans.”

CBD sprays (which have a higher bioavailability) have been deemed safe at daily dosages of 2.5mg of up to 2 weeks.


Some CBD users do report drowsiness upon administration of CBD oil. However, CBD is used as a sleep aid, which suggests that perhaps it is best administered at night.

Many medications carry drowsiness warnings, especially if they interact with the brain, blood pressure, or central nervous system. CBD interacts with all three, although it should be noted that it is not classed as a medication.

Additionally, some CBD users will experience idiosyncratic side effects as a result of their individual makeup. These effects cannot be attributed to CBD, as they are unique to the individual.

Dry Mouth

CBD users often report dry mouth, referred to by scientists as xerostomia. This can occur due to the way CBD interacts with the endocannabinoid system.

This study conducted in 2006 found that the submandibular gland (which produces saliva in the mouth), contained type 1 and 2 cannabinoid receptors. Of course, CBD interacts with these receptors, causing the endocannabinoid “anandamide” to be overproduced.

Anandamide limits the production of saliva when it binds to CB1 and CB2 receptors, resulting in dry mouth. To combat this, drink water and eat something you enjoy. The anticipation of the food will cause saliva to be produced, which may alleviate the feeling of ‘cotton mouth’ that some users report.

Low Blood Pressure

Reportedly, higher doses of CBD are capable of causing small drops in blood pressure. Typically, this will occur within a few minutes of administering the CBD, and the subsequent feeling of lightheadedness tends to dissipate after about half an hour.

If you’re looking at taking CBD oil and you are currently prescribed medication for blood pressure, make sure to ask your doctor about any potential interactions before buying a SmartCBD product.

Parkinson’s Disease (Increased Tremors)

Early research has suggested that people with Parkinson’s Disease may experience increased tremors at especially high doses of CBD.

If you suffer with Parkinson’s Disease and wish to buy SmartCBD products to treat your tremors, make sure you stick to the lowest dosage recommended by your doctor until you know how the substance affects your tremors.


CBD may interact with certain medications, so if you are concerned, be sure to let your doctor know that you are taking CBD.

Below are a number of popular medications and their interactions with CBD.

  • Fluoxetine (Prozac)
    This medication is an antidepressant used to alleviate the symptoms of depression by improving sleep, mood, energy levels, appetite, and helping the individual regain interest in everyday life. Ask your doctor whether you need to change your fluoxetine dosage if you decide to start taking CBD at the same time.
  • Warfarin
    This medication is a blood thinner, and may be temporarily aggravated by CBD (similar to taking a double dose of Warfarin.) Once CBD is excreted from the body, coagulation and platelet count should go back to normal. However, make sure to consult your doctor before adding CBD to your daily medication repertoire.
  • Risperidone
    This antipsychotic medication is used primarily to treat mild schizophrenia, bipolar disorder, and ASD. Some users of both Risperidone and CBD have reported severe panic attacks/increased psychotic side effects as a result of substance interaction. It is recommended to avoid CBD if you are taking any strong antipsychotic medications, such as Risperidone and Haloperidol.
  • Clobazam
    This medication is used to treat epilepsy and seizures. As it stands, CBD has shown a capacity for reducing seizures in humans, and may therefore interact with Clobazam in a negative way. Before taking CBD, consult the doctor who prescribed your Clobazam to ask if it is safe for you.
  • Nyquil
    This popular medication, used to treat cold and flu, already carries a drowsiness warning. Used in conjunction with CBD, patients may experience extreme fatigue, confusion, and tiredness. It’s best to avoid using CBD (which may function as a sleep aid) alongside medications which also carry a drowsiness warning.
  • Beta-blockers
    Beta-blockers are a class of medication used to treat high blood pressure, anxiety, heart problems, and even migraines. CBD slows down the heart rate, just like beta-blockers do. If you take Atenolol, Bisoprolol, Propranolol, or any other beta blockers, it’s recommended that you stay away from CBD (or at least consume it in moderation and only after consultation with your prescribing doctor).


It’s important to remember that often, we focus on only the negative side effects of a substance. Although you should always ensure you’re not taking CBD if it’s going to interact with an existing health condition or medication, it’s vital to understand the benefits CBD can bring if it is suitable for you.

Interested? Read more on our about page, here.

CBD products from SmartCBD

Interested in buying high-quality, natural CBD-rich products? See SmartCBD’s range of oils, balms, and pastes here.