Medically Reviewed by
Jason Crawford

Article Last Updated on January 5, 2023

Ever since the legalization of industrial hemp (Cannabis Sativa L.) in the United States, the use of medical marijuana and other cannabis products has significantly increased. 

The hemp plant contains many cannabinoids of which cannabidiol (CBD) is present at the largest concentrations, while levels of the psychoactive cannabinoid tetrahydrocannabinol (THC) are naturally very low.

As the main source of cannabidiol (CBD), the legal cultivation of hemp has kickstarted the rise of CBD products, namely CBD oils and tinctures. Even though not officially approved by the US Food and Drug Administration (FDA), the use of CBD oil has been steadily increasing due to its beneficial health effects on some medical conditions, like chronic pain, anxiety, and insomnia.

CBD oil is known as a product that’s well-tolerated by most people, but it’s also known to cause certain side effects when it interacts with some drugs, so certain people need to be careful when taking it. In this article, we’ll discuss why CBD oil interacts with some medications in this way and who should take it with caution.

CBD Oil Is Safe On Its Own, But It Can Influence How Some Medications Are Processed

As you may already know, the way the cannabis plant interacts with the human body when we consume cannabis products is through the endocannabinoid system and its receptors. THC binds directly to the receptors, which is how it produces the mind-altering effects, while CBD doesn’t bind to them fully and has calming and anti-inflammatory effects.

Research shows that CBD oil is safe on its own and it’s pretty well tolerated by most people, regardless of age – children, as well as older adults, can tolerate it. It can rarely cause some side effects, mostly an upset stomach and diarrhea, as well as nausea.

However, CBD can interact with certain over-the-counter and prescription drugs and it’s all connected to how the human body breaks down foreign substances.

What Is the Cytochrome P450 (CYP450) System and How Does It Work?

When you ingest any type of substance, including medication and CBD oil, the body needs to metabolize it or break it down into smaller compounds in order to use them more efficiently. For example, when you eat food, your body breaks down the carbohydrates into sugars and the proteins into amino acids.

This process happens mainly in the gut and the liver, where certain enzymes that are naturally produced in the body are responsible for breaking down the substances that are ingested. Additionally, the liver is responsible for getting rid of all the toxins in the body.

When you ingest CBD oil, first it needs to go through the digestive system where it gets broken down. Then, it travels through the bloodstream before it gets to the liver where it’s further metabolized by the so-called cytochrome P450 system.

The cytochrome P450 is a system that consists of a class of over 50 liver enzymes whose role is to process and eliminate toxins. In fact, these enzymes are responsible for breaking down about 60% of the medications that are ingested.

However, some substances, including CBD oil, can impair the rate at which these enzymes metabolize foreign substances by slowing down or speeding up the process. This chain reaction is what leads to drug interactions.

CBD Oil and CYP450 Enzymes

The CYP450 enzymes in the liver are responsible for breaking down some cannabinoids, including CBD, as well as certain medications. Within this family of enzymes, one subtype of enzymes called CYP3A4 is specifically tasked with this job

This means that this particular subtype of enzymes should break down both CBD and certain meds. The catch is that CBD will act as an inhibitor to the CYP3A4 enzymes and won’t allow them to process these medications properly, as the process will be too slow. 

Therefore, when the body is processing the meds too slowly, you may end up with a high dose of meds in your system even if you’re taking the right dosage. This may lead to more pronounced effects and even side effects. 

One interesting fact is that there are also other substances that inhibit the CYP3A4 enzymes, some of which can speed up the metabolizing process of the enzymes. When the meds are processed too fast, your normal dose won’t have any effect on you and will lose its efficacy because it’s eliminated before your health issue is treated.

What We Know So Far About CBD Oil Drug Interactions

So far, we know that certain medications that are metabolized by the CYP3A4 enzymes can react with CBD oil.

The Indiana University Department of Medicine lists the following classes of medications:

  • Steroids
  • HMG CoA reductase inhibitors
  • Calcium channel blockers
  • Antihistamines
  • Prokinetics
  • HIV antivirals
  • Immune modulators
  • Benzodiazepines
  • Antiarrhythmics
  • Antibiotics
  • Anesthetics
  • Antipsychotics
  • Antidepressants
  • Anti-epileptics
  • Beta-blockers
  • PPIs
  • NSAIDs
  • Angiotensin II blockers
  • Oral hypoglycemic agents
  • Sulfonylureas

If you’re on any prescription medications or frequently take some over-the-counter meds, it’s recommended that you get medical advice from your doctor in order to use CBD oil safely. They should be able to come up with a solution that will fit your particular situation and find a way to use both CBD oil and your regular medications.

Who Shouldn’t Take CBD Oil?

In recent years, many clinical trials on the health effects of CBD were conducted. A lot of them concluded that CBD could be a successful treatment for the symptoms of many medical conditions. In fact, in 2018, Epidiolex, the first pharmaceutical-grade CBD oil, was approved by the FDA for the treatment of childhood epilepsy.

However, seeing as CBD can still interact with certain classes of medications, some people need to use it with caution.

For one, people who have low blood pressure should be careful when taking CBD oil. One of the benefits of CBD is that it can temporarily lower your blood pressure during stressful times. However, for individuals who already suffer from low blood pressure (hypotension), it can cause additional side effects like lightheadedness and drowsiness.

Even though there isn’t enough conclusive evidence, it’s generally recommended to consult with your doctor about using CBD oil if you’re breastfeeding or pregnant. Some studies suggest that low concentrations of cannabinoids can still be detected in breast milk in regular cannabis users, so it’s advised to reduce your exposure to cannabinoids just to be on the safe side.

When In Doubt, Look for the Grapefruit Warning

If you’re not sure if the medication you’re taking can react with CBD, you can always use the grapefruit warning on the medication label as a guide

Some medications have a grapefruit warning printed on the label which means that you should avoid consuming grapefruit while you’re taking them because some compounds in grapefruit, just like CBD, can inhibit the work of the CYP3A4 enzymes

In fact, over 80 types of medications can react with grapefruit and similar citrus fruits (Seville oranges, pomelos, and tangelos). Some of these medications are blood thinners, corticosteroids, pain medications, cholesterol medications, and others.

Side Effects of CBD Oil Caused by Potential Drug Interactions

If you’re planning to use CBD oil along with your usual meds, it’s best to do so under your doctor’s supervision. However, monitoring your body’s reaction to this combination is very important. If you feel drowsiness, nausea, and sedation, you’re probably experiencing more pronounced effects of your regular meds due to the interaction with CBD. In this case, stop taking CBD oil immediately and consult with your doctor for further steps.

Do CBD Topicals Have the Same Potential Interactions?

Topicals, like CBD creams and lotions, shouldn’t have any interactions with certain medications as they’re not designed to be absorbed in the bloodstream and only work locally. That said, if you’re using transdermal patches, which are designed to enter the bloodstream, you could have some interactions. The same applies to edibles (chocolates, gummies, candies), capsules, and vapes, as they all deliver CBD to the bloodstream.

The Takeaway – Before Using CBD Oil, Consult With a Healthcare Provider

CBD oil is a wonderful substance that can be used to treat numerous symptoms, but it does have its Achilles heel. If you’re on any prescription medication, it’s very important to consult with a healthcare provider before you start using CBD oil regularly. Due to the nature of its interaction with the liver enzymes, it’s recommended that you make an informed decision beforehand.

A passionate advocate for the benefits of cannabis. Fraser Horton, who has a background in botany and a strong love of nature, has spent years researching how cannabis affects the body and mind. He established Leaf Nation in 2020, where he has devoted himself to educating people about the legalisation of marijuana and its safe and responsible use. Fraser is committed to highlighting cannabis’ potential for improving wellness and working to dispel the stigma associated with its use.


The information presented on this page is provided as a public service to aid in education and is derived from sources believed to be reliable. Readers are responsible for making their own assessment of the topics discussed here. In no event shall Leaf Nation be held reliable for any injury, loss or damage that could happen if using or abusing drugs.