cbd oil cannabisOne of the most medically useful compounds found in marijuana is cannabidiol (CBD).  This is a non-psychoactive substance that, unlike THC, does not cause a euphoric high or mind-altering effects.

CBD interacts with the endocannabinoid system, which has widespread effects on the entire body. It has anticonvulsant, antipsychotic, antiemetic, and analgesic properties, among many others. Cannabidiol usually comes in the form of CBD oil, extracts and concentrates and has been touted as a safe alternative to mainstream opioid medicine.

Is CBD Safe?

CBD’s safety was tested on adults in a number of small-scale studies. It has been documented as being well tolerated across a wide spectrum of doses without significant side effects to the central nervous system or effects on vital signs and mood among people who use it at various levels.

Following a number of studies, CBD is considered to be well-tolerated in humans. This is true even when taken at high doses or for long periods of time. Unlike THC, CBD extracts and CBD oils do not have any psychoactive side effects.

However, as with any compound that enters the body, there has been a record of mild side-effects. The most common side effect noted in these studies has been tiredness. Some people have experienced diarrhea as well as changes in appetite or weight.

How Much CBD Oil is Too Much?

High doses of CBD can be safely used without negative effects. Although some patients will benefit from doses as low as 15mg, up to 1500mg per day have been reported as safe.

Studies show that the lethal dose of CBD is so high scientists are not even sure of the exact amount of CBD needed to cause human mortality. There are no known reports of death caused by CBD extracts. The best guess was provided by a 1981 study on rhesus monkeys which demonstrated that a dose of 200mg per kg of body weight caused death.

Scientific Studies on the Side Effects CBD

A review of 132 scientific studies performed in 2011[1] concluded that CBD is generally safe and does not severely impair bodily functions. Some of these unaffected processes include body temperature, heart rate, blood pressure, motor functions, psychological function, and gastrointestinal transit.

One of the few serious effects from CBD use included an impact on the liver metabolism of certain drugs, a possible worsening of HIV symptoms, and a potential impact on fertility.

In 2017 another group of researchers reviewed the safety and side effects of CBD. They used the many studies on CBD which were conducted between 2011 and 2017. These provided an additional 74 articles to examine. These researchers found the same mild side effects of CBD as other studies. They included fatigue, diarrhea, and appetite changes.

CBD Effects on the Liver

One potential side effect of CBD is an effect on the liver’s ability to process certain drugs and medications. This was demonstrated in 2011, in the study mentioned above, which found that CBD was a “potent inhibitor” of certain liver enzymes involved in drug metabolism. This class of liver enzymes is called cytochrome P450 and is involved in metabolizing a number of drugs.

CBD inactivates specific forms of this enzyme, which reduces the liver’s effectiveness in processing certain drugs. This result is very similar to the way that grapefruits can interact with certain medications. Therefore, If you will be taking CBD, it will be important to speak with your doctor before combining prescription medications with CBD.

CBD AND Diarrhea

A 2015 report[2] on CBD for epilepsy also showed diarrhea to be a common side effect of CBD treatment. However, it remains unclear whether this side effect is specific to those with epilepsy, as it was found in other studies that CBD does not impact gastrointestinal transit time (which would be shortened in the case of diarrhea). Additionally, it is also important to note that the doses used in this particular study were very high.

CBD AND Fatigue

In a Dutch 2014 study[3] of medical marijuana users, fatigue was experienced by patients treated with high-CBD strains. However, the cannabis used in this experiment contained some THC. Therefore, it is unclear how much of the drowsiness can be attributed to CBD, as THC is known to cause sleepiness. Fatigue was also the most frequently reported side effect of CBD found in the AAN report on its effectiveness on epilepsy.

CBD AND Appetite

A few studies have reported changes in appetite resulting from CBD use. For example, the Dutch study from 2014 found out that people who used a high-CBD strain of cannabis reported modest changes in appetite. However, this was another case where appetite changes were stronger in patients who used a high-THC strain. As there was still some THC in the high-CBD strain, it is difficult to determine whether these effects were solely caused by CBD.


The 2011 study on the side effects of CBD oils and concentrates on HIV patients led to mixed results. Problems caused CBD included potentially worsening the progression of HIV. They also found results suggesting it may make infection with HIV easier when exposed to the virus. However, the researchers also noted that some studies found a biphasic effect: a beneficial effect at low doses, and a negative effect at high doses.

Using CBD safely

Like all drugs, in order to minimize the chances of experiencing side effects from CBD, it is important to use the correct dose. Also, be certain any drugs you are currently taking do not interact with CBD.

When it comes to any medication, it’s always better to use the smallest dose and work your way up. Because side effects naturally increase with dosage, a smaller dose means you will have a lesser chance of experiencing negative side effects.

If you are experiencing side effects, you may be using too high of a dose. You can use dose titration to find a dose that produces the best result but does not produce bad side effects. It is also very important to speak with your doctor about any drug interactions between CBD and any medications you are already taking.

[1] Bergamaschi MM, Queiroz RH, Zuardi AW, Crippa JA. Safety and side effects of cannabidiol, a Cannabis sativa constituent. Curr Drug Saf. 2011 Sep 1;6(4):237-49. Review. PubMed PMID: 22129319.

[2] Report published by the American Academy of Neurology

[3] Brunt TM, van Genugten M, Höner-Snoeken K, van de Velde MJ, Niesink RJ. Therapeutic satisfaction and subjective effects of different strains of pharmaceutical-grade cannabis. J Clin Psychopharmacol. 2014 Jun;34(3):344-9. Doi: 10.1097/JCP.0000000000000129. PubMed PMID: 24747979.