CBD Oil Side Effects: Is It Safe?

Last Updated: August 2020

Cannabidiol (CBD) oil is growing rapidly in popularity as a natural alternative to over-the-counter and prescription pain and anxiety medications.

Although overall it’s very safe, CBD oil does have some side effects in certain individuals.

This article will review what CBD oil is, the side effects that have been reported in scientific literature, and the CBD oil’s potential drug interactions.

What is CBD oil?

CBD oil is a supplement made from cannabidiol, a cannabinoid that is extracted from the hemp plant. Unlike marijuana and its other main cannabinoid component, tetrahydrocannabinol (THC), CBD does not get you high.cb

However, it does have a number of potential health benefits. CBD is widely used as a safe, non-addictive pain reliever. It may also help relieve stress, anxiety, and insomnia.

CBD works by acting on the body’s innate endocannabinoid system, which is part of the larger central nervous system. The endocannabinoid system is composed of endocannabinoids, which are cannabinoids that are naturally synthesized within the body, and cannabinoid receptors.

This system has roles in homeostasis, or maintaining a balance of biological processes in response to external, environmental changes. It can affect pain signaling, memory and focus, appetite, stress levels, sleep, immune health, and even reproductive function.

However, phytocannabinoids (plant cannabinoids)—like CBD and THC found in marijuana—can also act on the endocannabinoid system to potentially help with some of these functions.

Side effects of CBD oil

According to most research, CBD oil is extremely safe to take and most people experience no side effects at all. In fact, according to existing research, doses of up to 1,500 mg per day are well-tolerated by most people with no detrimental side effects.

Remember, though, that this is a relatively new field of study, and as our knowledge of CBD advances we may find new side effects and complications of CBD use.

Here are some of the most commonly reported side effects of CBD oil.

Appetite and weight changes

It’s well known that smoking marijuana or ingesting marijuana edibles can increase appetite and give you “the munchies.” In fact, the prescription drug marinol—which is commonly given to cancer and HIV/AIDS patients to stimulate their appetite and reduce nausea—is derived from marijuana.

However, it looks like—at least in a small subset of people—CBD may have a similar effect. Unfortunately, this increase in appetite may also lead to unwanted weight gain.

If this is happening to you, you can try lowering your dose of CBD, discontinuing its use, or stocking up on healthier, more satisfying snack options like fruits, veggies, hard-boiled eggs, or nuts and seeds.

On the other hand, most people report a reduction in appetite when taking CBD oil. In fact, a reduced appetite is more common with CBD, as THC appears to be the main culprit behind the munchies.

If you notice, however, that you’re losing too much weight on CBD because of your suppressed appetite, you may want to lower your dose or add some more high-calorie foods to your routine.

Fatigue and sedation

In one observational study, a small fraction of participants had to stop using CBD because it had a sedative effect on them, making them feel excessively fatigued and sluggish. It’s thought that this occurs because CBD may help reduce blood pressure.

Although a slight sedative effect can be beneficial, especially if you’re using CBD to help manage anxiety or promote better sleep, too much can interfere with your daily life.

In this case, you should lower your dose of CBD to see if the fatigue improves, or discontinue using it completely if you’re experiencing excessive fatigue on a low dose.

Dry mouth

Some people have also reported experiencing dry mouth and increased thirst after taking CBD. Cannabinoids such as CBD and THC can actually inhibit saliva production, which is the likely culprit of this side effect.

To help relieve dry mouth, keep fluids nearby and stay well-hydrated throughout the day.


Although uncommon, one of the most unfortunate side effects of CBD may be diarrhea. The mechanism is not exactly clear, but it’s possible that CBD may have a relaxing effect on the muscles in your digestive system, allowing matter to travel through your gastrointestinal tract more rapidly.

Worsening anxiety

CBD oil is often used to help manage anxiety. However, in very rare instances, it may actually worsen anxiety and feelings of panic.

One way it works to reduce anxiety is by acting on the CB1R receptor, an endocannabinoid receptor that helps regulate feelings of fear and anxiety. In most cases, acting on this receptor causes decreases in anxiety, stress, and the fear response to external stressors. However, in rare instances, it may actually cause the opposite reaction.

If you find that your anxiety worsens after taking CBD, you should stop taking it.

Liver toxicity

Although it’s never been noted in humans, liver toxicity is one potential side effect of extremely high doses of CBD.

In one animal study, mice who received extremely high doses of CBD experienced liver damage. However, the doses given to these mice were astronomically high and force fed to the animals. It would be nearly impossible for a person to consume an equivalent amount of CBD orally to experience the same effects.

However, the potential for risk is there, as some human trials have noted elevated liver enzymes with CBD use.

Medication interactions

One serious concern with CBD oil is the possibility for medication interactions. These interactions have the potential to be severe by either weakening or amplifying the effects of the medication.

Most drug metabolism occurs in the liver. Enzymes known as cytochrome P450 enzymes (CYP450) actually convert these drugs into substances that can be excreted from the body safely. CYP450—and more specifically, the enzyme CYP3A4—is also responsible for the metabolism of CBD.

Unfortunately, when CBD and certain medications are in your system, CBD may be prioritized by CYP450, meaning the prescription medication lingers longer in the body and may have stronger effects. Alternatively, certain medications may keep your body from being able to process CBD effectively, amplifying the effects of CBD.

Identifying which medications CBD may interfere with can be tricky, though. As a general rule of thumb, CBD may interfere with any drugs that also interact with grapefruit.

Grapefruit and some other citrus fruits—like pomelo and tangelo—contain compounds called furanocoumarins, which affect the CYP450 enzymes in similar ways as CBD and either strengthen or weaken the effects of the medication. In fact, grapefruit can have such a powerful effect that one of the researchers studying the link between grapefruit and medication effectiveness has said that taking one pill with a glass of grapefruit juice can be equivalent to taking five of the same pills with a glass of water.

Some medications that carry this warning are:

  • Cholesterol lowering drugs (statins), including simvastatin and atorvastatin, and their brand name counterparts
  • Blood pressure lowering medications like nifedipine and its brand name counterparts
  • Organ transplant rejection drugs like cyclosporine, sirolimus, and their brand name counterparts
  • Anti-anxiety medications like buspirone and its brand name counterparts
  • Corticosteroids like budesonide and its brand name counterparts
  • Heart rhythm drugs like amiodarone and its brand name counterparts
  • Antihistamines such as fexofenadine and its brand name counterparts
  • Antibiotics such as doxycycline, erythromycin, and their brand name counterparts
  • Anti-seizure drugs, like levetiracetam and its brand name counterparts
  • Blood thinners, including clopidogrel and its brand name counterparts
  • Heartburn and nausea medications, including cimetidine, domperidone, and their brand name counterparts
  • Erectile dysfunction medications like sildenafil and its brand name counterparts
  • Pain medications, including fentanyl, oxycodone, colchicine, and their name brand counterparts
  • Prostate medications, including tamsulosin and its name brand counterparts

However, this is not a complete list. There are over 80 drugs that have this warning, and that therefore may interact with CBD. It’s extremely important to consult your doctor before starting CBD if you are taking any of these medications.

Your doctor or pharmacist can help you determine if a medication has a grapefruit warning, as well as provide guidance about timing and dosage of CBD to help minimize your risk of potential drug interactions.

If taking CBD for pain, you may also want to consider a topical cream or lotion containing CBD. Topical CBD carries a very low risk of entering the bloodstream and interfering with CYP3A4 or medication metabolism.

Because of this interplay of grapefruit, CBD, and CYP3A4, you may also want to avoid grapefruit and grapefruit juice while taking CBD even if you’re not taking any prescription drugs. Grapefruit juice may interfere with your body’s ability to process and metabolize CBD, potentially amplifying or weakening its effects—both positive and negative.

Who shouldn’t use CBD?

CBD is very safe and poses little risk of causing side effects or complications. Regardless, there are certain people who should avoid CBD. If you fit into any of these categories, you should avoid taking CBD unless you get the okay from your doctor or healthcare team:

  • People on medications that may interact with CBD, because these interactions may cause severe complications
  • Pregnant or breastfeeding women, because little is known about how CBD may affect developing fetuses or infants
  • People with low blood pressure, because CBD has a potentially blood pressure lowering effect
  • People with liver disease, because very high doses may be toxic to the liver
  • People with kidney disease or who are on dialysis, because this may affect the body’s ability to get rid of CBD through the kidneys
  • Underweight people or those with severely diminished appetite or restrictive eating disorders, because of CBD’s potential appetite suppressing effect

As a general rule of thumb, CBD is perfectly safe for healthy people to take. However, if you have any medical conditions or are taking any prescription medications, it’s a good idea to talk to your doctor about CBD before you start taking it.

Minimizing side effects

To minimize your risk of experiencing either a side effect or a medication interaction when using CBD oil, there are a few things you can do.

First, talk to your doctor about adding CBD oil to your routine. Your healthcare team can help you identify potential medication interactions that may occur and may even be able to provide some insight regarding dosing and which products would be best for you.

Next, make sure you choose a high-quality CBD product. The highest quality CBD oils are derived from U.S. grown, organic hemp, contain few unnecessary additives, and are third-party tested to help ensure the quality and purity of the product. Because side effects are uncommon, experiencing severe side effects from CBD oil may be a sign that the oil contains some poor-quality or irritating ingredients, or ingredients that you may be allergic or sensitive to.

Finally, if you’re new to CBD, it’s important to start with the absolute smallest dose you can and work your way up slowly, as needed. A starter dose may contain 20-25 mg of CBD. Take this small amount daily, assess how it is helping you after 2-3 weeks, and then increase your dose slowly as needed.

If you do experience uncomfortable or harmful side effects that you believe are caused by CBD, discontinue using the product immediately and make an appointment with your doctor to discuss this reaction.


CBD oil is very safe for the vast majority of people. Research shows that doses up to 1,500 mg daily have had no significant adverse effects on people.

However, some people may experience side effects from CBD, including appetite changes, fatigue, diarrhea, or worsening anxiety. In animal studies, rats receiving extremely high doses of CBD have suffered liver damage.

CBD may also interfere with certain medications.

To minimize your risk, talk to your doctor before starting CBD oil, choose a high-quality product, and start with the lowest dose possible, gradually increasing as needed. However, you can rest easy knowing that most people experience no side effects at all.

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