Can I Use CBD While I’m Sick?

Cannabinoids like CBD are in an odd place right now; on the brink of widespread acceptance but lacking sufficient clinical proof. Their popularity is growing at a tremendous rate. The literature regarding their effects in the body is starting to increase and more, albeit small studies, are being conducted in humans suggesting, as previously thought, that CBD does possess a number of potentially exciting therapeutic qualities, but we are still very much in the dark in a number of areas.  

As the popularity and awareness of CBD continues to increase, many turns to CBD products when they are ill often for perceived anti-inflammatory, anti-anxiety or analgesic benefits.

Yet, as with all new areas of science, there is much we still don’t know about how CBD interacts with human physiology, and more importantly, how CBD interacts with other compounds commonly used to treat illness.


Relative Contraindications

In medicine, the term ‘contraindication’ means a condition or factor that serves as a reason to withhold a certain medical treatment due to the harm that it would cause the patient. Contraindication is the opposite of indication, which is a reason to use a certain treatment. The more specific term ‘relative contraindications’ refers to a situation in which two treatments (usually two pharmaceutical drugs) should NOT be used at the same time due to drug interactions that can alter the expected physiological outcomes.

Recently the FSA announced strict and welcomed guidelines on CBD products which includes having a specific medical warning that CBD products should not be used by anyone on existing medications and there is good scientific reason for this – this is a prime example of relative contraindications.

Cannabinoids, specifically CBD, interact with a family of enzymes in the liver known as the P450 family of enzymes. These enzymes are very important for metabolising (breaking down/altering) toxic compound as well as up to 60% of drugs that enter your system. Depending on the drug, large quantities may be metabolised and broken down in your liver before ever reaching your blood and doctors prescribe your dose of medications taking this ‘first-pass’ liver metabolism into account as well as the general health of your liver and p450 enzyme system. As can probably be guessed, an unhealthy liver typically processes drugs at a slower rate so your drug dose will be adjusted by your doctor based on a liver function test.

Now, the part that brings up issues. CBD essentially sequesters or otherwise ‘pre-occupies’ P450 enzymes so when you ingest other drugs they are not broken down to the same degree in the liver, thus inappropriately increasing the amount of active drug that ultimately reaches your blood stream and/or increasing the time it takes to process drugs in the liver.

Cannabidiol can inhibit the P450 enzyme system’s ability to metabolise certain drugs, leading to an overall increase in processing times

While this is unlikely to be immediately life threatening, some drugs, especially anti-psychotics/depressants, are dose-tailored very closely to each patient and an inappropriate spike in the blood can cause havoc to an individual’s treatment regime.

Interestingly, compounds in grapefruit have a similar affect as on the P450 system as CBD which is why you may sometimes see a ‘grapefruit’ warning on drug packaging. If you do see this warning, odds are CBD will impact the drugs metabolism in the same way.


Based on our current understanding any drug/therapeutic compound which is metabolised or otherwise interacts with the P450 system, may be adversely affected by CBD use. This includes:

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

This list is based on our CURRENT understanding and is likely to change over time so expect that a number of different drug classes will be added in the future. As it stands, the list includes a huge number of commonly consumed drug types.

A note on ‘pro-drugs’:

Aside from the list above, a class of drugs sometimes referred to as pro-drugs may be impacted by CBD use. Pro-drugs are drugs which need to be metabolised to produce the therapeutic compound.

You ingest an inactive compound and once in the body, it is processed into the active drug. If this process happens to rely on the P450 system, then you can end up with too little of the active drug to provide a therapeutic effect. Codeine is a common example of a pro-drug which is metabolised into morphine in the body. A number of ADHD medications also function in this way.


We do stress that individuals who are on existing medications do not take CBD products. If your curiosity still persists then please consult your primary physician before proceeding.



Unless you have impaired liver, function or are using other medications there is no clear reason why you shouldn’t use CBD while you are mildly sick. Many seek out CBD products to use precisely because they are sick and if CBD works for you, providing a benefit to your mind or body whether that be with pain management, mood regulation or anything else, then more power to you. But if you are sick AND on other medications proceed with caution. Our advice is to always speak to your doctor.

If you need any help or support regarding CBD products speak to our experts here

Leave a comment

All comments are moderated before being published