• Research has not confirmed whether CBD oil may be used as needed.
  • The efficacy of CBD may depend on the individual and CBD’s capacity to affect the body systemically(1).
  • To know if CBD is safe to use, consult a healthcare professional.

CBD Usage and Dosage

No research has defined a standard daily dosage for CBD, including CBD oil. However, several studies tested the efficacy of CBD on different diseases in varying doses.

For example, a study observed that a daily intake of 10 to 12mg of CBD may result in less frequent seizures among individuals with epilepsy(2).

Another study from the Journal of Cannabis Research noted that some individuals take CBD in low doses to manage their anxiety and stress(3).

Factors That Determine the Best Time to Take CBD

The best time to take CBD may vary for each individual.

Studies on sleep showed that CBD may both improve and worsen sleep quality. Individuals with insomnia experienced better sleep after taking CBD(4).

A 2017 study hypothesized that CBD may help with daytime sleepiness. However, it may also cause sleep issues when taken for extended periods(5).

Therefore, it may be best for individuals to identify the effects of CBD before use.

CBD Absorption

As with any medication, CBD comes in different forms, which differ in how the body processes the compound.

Factors That Affect CBD Absorption

CBD’s effectiveness may depend on the CBD product’s bioavailability.

Bioavailability measures the probability at which the body absorbs a drug.

In animal studies, oral and topical CBD showed high bioavailability, suggesting that both administration methods may also work for individuals(6).

However, a study compared different oral methods and observed that CBD bioavailability decreases when the drug passes through the liver, which causes the first-pass metabolism(7).

The first-pass metabolism occurs when a drug’s efficacy is reduced before its therapeutic effects happen in a body(8).

Furthermore, a study that tested different CBD applications suggested that mixing CBD with mediums like emu oil may increase the cannabinoid’s bioavailability as a topical medication(9).

CBD’s bioavailability may also depend on an individual’s metabolism, age, and overall biological makeup.

Studies postulated that fatty acids in the body may help with CBD absorption(10).

When Does CBD Start Working?

The onset time of CBD is indefinite and may change depending on the CBD product’s pharmacokinetics.

How Long CBD Takes to Enter Your System

Topical CBD for pain, such as CBD oils, takes 10 to 15 minutes to enter the system(11).

However, the rate at which CBD affects the body systemically may increase when CBD is mixed with certain ingredients.

A 2013 study proposed that mixing CBD with silicon fluids and hyaluronic acid may help with skin absorption(12).

How Long Is CBD in One’s System?

The effects of topical CBD may last up to four hours(13). As for other CBD products, such as oral CBD, the lasting impact of CBD is inconclusive.

What Is CBD?

CBD or cannabidiol is a major phytocannabinoid found in Cannabis sativa L. Unlike THC, CBD is non-psychoactive.

Numerous research hypothesized that CBD may be considered for its anti-inflammatory and anxiolytic properties. However, evidence on the cannabinoid’s therapeutic potential is still scarce.

CBD may be sold in oral and topical forms, such as oils, lotions, gummies, and edibles.

CBD products may come in three types: full-spectrum, broad-spectrum, and CBD isolate.

Full-spectrum CBD oil contains all compounds of the cannabis plant(14).

Meanwhile, although broad-spectrum CBD oil also has all compounds of the cannabis plant, this CBD variant is THC-free. Individuals who experience adverse effects from THC may prefer broad-spectrum CBD(15)

CBD isolate is pure CBD, void of other cannabinoids and phytochemicals. 

CBD Benefits

CBD may be an effective medicinal alternative for individuals with neurological and mental illnesses, like multiple sclerosis and depression. CBD may also help individuals experiencing chronic pain(16).

A study on CBD’s effect on anxiety showed that CBD may alleviate stress among individuals for a certain period(17).

A study on sleep also observed that CBD may help manage insomnia temporarily(18). CBD may also promote good quality sleep, especially for individuals experiencing daytime sleepiness(19).

CBD Side Effects

Studies have reported that CBD may contribute to liver-related injuries. Therefore, CBD may harm the liver when taken to some extent(20).

Other common side effects of CBD are diarrhea, nausea, and fatigue. 

CBD Safety and Risks

A 2017 study reported that CBD’s common side effects in individuals with epilepsy may be more manageable than those caused by other medications(21).

However, the risk of CBD use may lie in the cannabinoid’s chemical composition. A study stated that cannabis-derived products, including CBD products, may contain heavy metals that could cause harm to their users(22).

As heavy metals are difficult to break down, they may increase the risk of cancer and neurological issues among individuals(23).

Therefore, individuals interested in CBD must read a CBD product’s Certificate of Analysis (COA), which contains a list of the product’s chemical composition. To access a CBD product’s COA, individuals may go to the respective CBD brand’s website.

Where Can I Buy CBD?

Several CBD products are currently available online. However, a study on CBD products observed that almost 70% of CBD products sold online are erroneously labeled(24).

Since the production of CBD products is not regulated correctly, product labels may contain false information. For example, some CBD products claim to have no THC even though they contain high amounts(25)

Before buying CBD products, individuals must first consult with a healthcare professional to avoid buying falsely advertised CBD products.


The U.S. Food and Drug Administration recognized the 2018 Farm Bill. The bill legalized hemp with low THC content with a 0.3% THC concentration in dry weight(26).

  1. A Systematic Review on the Pharmacokinetics of Cannabidiol in Humans. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6275223/
  2. Dosage Related Efficacy and Tolerability of Cannabidiol in Children With Treatment-Resistant Epileptic Encephalopathy: Preliminary Results of the CARE-E Study. https://www.frontiersin.org/articles/10.3389/fneur.2019.00716/full
  3. Reasons for cannabidiol use: a cross-sectional study of CBD users, focusing on self-perceived stress, anxiety, and sleep problems. https://jcannabisresearch.biomedcentral.com/articles/10.1186/s42238-021-00061-5
  4. Potential Effects of Cannabidiol as a Wake-Promoting Agent. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4023456/
  5. Cannabis, Cannabinoids, and Sleep: a Review of the Literature. https://pubmed.ncbi.nlm.nih.gov/28349316/
  6. A Systematic Review on the Pharmacokinetics of Cannabidiol in Humans. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6275223/
  7. Comparison of Five Oral Cannabidiol Preparations in Adult Humans: Pharmacokinetics, Body Composition, and Heart Rate Variability. https://www.mdpi.com/1424-8247/14/1/35/pdf
  8. First Pass Effect. https://www.ncbi.nlm.nih.gov/books/NBK551679/
  9. Cannabinoid Delivery Systems for Pain and Inflammation Treatment. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6222489/
  10. Ibid.
  11. Healing with CBD, page 210. https://drive.google.com/file/d/1AGlxnhS2SoFeOXEuysv75bd_C9pEnwsU/view
  12. Cannabinoid Delivery Systems for Pain and Inflammation Treatment. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6222489/
  13. Healing with CBD, page 210. https://drive.google.com/file/d/1AGlxnhS2SoFeOXEuysv75bd_C9pEnwsU/view
  14. Cannabidiol primer for healthcare professionals. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7340472/
  15. An emerging allergen: Cannabis sativa allergy in a climate of recent legalization. https://aacijournal.biomedcentral.com/articles/10.1186/s13223-020-00447-9
  16. Therapeutic Effects of Cannabis and Cannabinoids. https://www.ncbi.nlm.nih.gov/books/NBK425767/
  17. Cannabidiol in Anxiety and Sleep: A Large Case Series. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6326553/
  18. Cannabis, Cannabinoids, and Sleep: a Review of the Literature. https://pubmed.ncbi.nlm.nih.gov/28349316/
  19. Ibid.
  20. Cannabidiol Adverse Effects and Toxicity. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7052834/
  21. An Update on Safety and Side Effects of Cannabidiol: A Review of Clinical Data and Relevant Animal Studies. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5569602/
  22. Cannabis may contain heavy metals and affect consumer health, study finds. https://www.sciencedaily.com/releases/2021/12/211216150039.htm
  23. Ibid.
  24. Penn Study Shows Nearly 70 Percent of Cannabidiol Extracts Sold Online Are Mislabeled. https://www.pennmedicine.org/news/news-releases/2017/november/penn-study-shows-nearly-70-percent-of-cannabidiol-extracts-sold-online-are-mislabeled
  25. Ibid.
  26. Hemp Production and the 2018 Farm Bill
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