BlogIrradiated and non-irradiated medical cannabis - what's the difference?

Irradiated and non-irradiated medical cannabis - what's the difference?

11 min read

Sarah Sinclair

Irradiated and non-irradiated medical cannabis

Many medical cannabis products in the UK have undergone a process known as irradiation, but what is the difference between these and non-irradiated products? Here’s everything you need to know.


The debate between irradiated and non-irradiated medical cannabis can be a controversial topic.

Irradiation can help ensure that medical cannabis products are free from contaminants and unwanted microbes, which could present a health risk for those with certain health conditions.

But some patients are concerned about the lack of research that has been done on the effects of irradiation on cannabis and the potential impact on the end product. 

Here we take a deep dive into the difference between irritated and non-irradiated medical cannabis — and the pros and cons of each.

What is irradiated medical cannabis?

In order to be prescribed in the UK, medical cannabis products must meet strict EU-GMP guidelines. In order to help producers meet these standards, many products on the market have been through a process known as irradiation.

What is irradiation?

To put it simply, the process of irradiation typically involves exposing a substance or material to a source of radiation. The energy produced by the radiation helps kill unwanted organisms and  reduce what is known as the microbial load.

The specific process which is used can vary depending on a number of different factors such as the type of material, the desired outcome, and the radiation source used. 

Irradiation is not exclusive to the production of medical cannabis, it is also commonly used in food processing and other industries to help reduce contaminants and ensure products are safe for human consumption.

Other examples of when irradiation might be used include in the sterilisation of medical equipment and supplies, scientific research, and for environmental reasons, such as the purification of water or soil to decontaminate that which might be polluted with harmful pathogens or microorganisms.  

Irradiated food is generally considered to be safe and has been endorsed by a number of bodies such as the World Health Organization (WHO), the European Union (EU), and the Food and Drug Administration (FDA).

Why is it used in the medical cannabis industry (and elsewhere)?

Like all plants, cannabis crops are prone to contaminants such as fungi, viruses, mites, and bacteria which also thrive in natural environments. 

Many of these microbes are not harmful to humans, but some can be, especially in people who have a weakened immune system, for example, due to having an autoimmune condition or taking immunosuppressant medication. 

Autoimmune conditions include inflammatory bowel disease (IBD) —such as Crohn’s disease and ulcerative colitis—multiple sclerosis (MS), rheumatoid arthritis and fibromyalgia, all of which medical cannabis is prescribed for in the UK. 

Pulmonary diseases caused by moulds and bacteria in cannabis are a particular risk to individuals who administer their medication through vaporisation, during which it is inhaled directly into the lungs. 

There is also the risk of residue from pesticides and fertilisers used during the growing process which may be harmful to human health. 

Irradiation is a form of sterilisation which is used to help kill unwanted microbes and organisms and reduce what is known as the microbial load with the aim of making products safe for consumption, although it does not entirely reduce the risk. 

There are different types of sterilisation including Gamma irradiation, UV irradiation, chemical treatment and processes known as autoclaving and pasteurisation, all of which have different effects on the end product. 

What are the different types of medical cannabis irradiation?

Different types of radiation which are typically used in the production of medical cannabis include Gamma radiation, UV, and electron beams (e-beams). 

Gamma radiation works by disrupting the DNA of microbes and preventing them from reproducing. Gamma rays have a short wavelength, similar to light, but are invisible to the human eye.

Gamma rays cause ionisation when exposed to humans, altering cells and DNA, which can lead to ill health and cause cancer.

Beta or eBeam electron generation is also widely used for the sterilisation of medical devices, pharmaceuticals and cosmetics.

Electron beams are not from a radioactive source, but are what is known as particle accelerators. In this case, the particles being accelerated are electrons and the beam generated is the equivalent of beta radiation, which is used to bring about changes in the properties of a material. 

The process of irradiation in medical cannabis manufacturing 

Before undergoing the irradiation process, the cannabis is prepared by drying, curing and trimming depending on the desired end product. 

These products are then placed in containers or trays and exposed to the radiation source. The length of exposure or appropriate irradiation dose is determined based on a number of factors such as the type of product, the desired microbial reduction and regulatory standards. This dose is usually measured in units of Gray (Gy), which represent the amount of radiation energy absorbed per unit mass of material.

To ensure the safety of the products, quality control measures are implemented throughout the process such as monitoring the dose and confirming microbial reduction. 

After the irradiation is complete the products will undergo additional processing such as packaging and labelling, before being distributed to pharmacies ready for prescription. 

What effect does irradiation have on the cannabinoid and/or terpene content?

There is limited research examining how the irradiation process affects the compounds in the end product.

In some studies, low doses of Gamma irradiation have been shown to have relatively little effect on major cannabinoids such as CBD and THC, particularly compared to other forms of sterilisation (e.g autoclaving, pasteurisation, UV radiation, and chemical treatment) which have been shown to cause greater deterioration of cannabinoids.

However, as heat is generated during the irradiation process, it can impact the levels of terpenes in the product. Some studies have suggested that irradiation may reduce the terpene content by around 20-30%, although this is generally not thought to be to an extent which would impact its therapeutic effects. 

Different terpenes are affected by heat in various ways depending on their boiling and evaporation temperatures. For example, in some studies, the loss of terpenes such as myrcene and linalool was observed in some cannabis strains. 

What is non-irradiated medical cannabis?

Non-irradiated medical cannabis has not gone through the processes of sterilisation described above. 

In this case, producers often choose to rely on adhering to ​​good manufacturing practices to help minimise the risk of contamination and ensure their products undergo rigorous testing to achieve optimum safety and quality. 

Ensuring safety and quality in non-irradiated cannabis

Some experts believe that if the cannabis flower is grown in optimal circumstances, then it should not need to undergo irradiation in order to meet the standards set out by regulators. 

Having proper sanitation procedures in place can prevent the spread of pathogens, while maintaining controlled environmental conditions such as temperature, humidity, and airflow in the facility can help inhibit the growth of microbes and minimise contamination risks throughout the production process. 

Once the product is ready, airtight packaging and appropriate storage temperatures can help prevent microbial growth and degradation.

Irradiated vs non-irradiated cannabis: pros and cons 

Advantages of irradiated medical cannabis 

For patients who have a weakened immune system or are at greater risk of respiratory issues, knowing that medical cannabis products have undergone irradiation offers some peace of mind that additional steps have been taken to help make them safe to consume.

The process of irradiation also ensures that the medical cannabis you are prescribed does not come with any of the hidden dangers of that which is bought illegally and from what is known as ‘grit weed’. 

Grit weed is a term used for cannabis which is contaminated with particulate matter, such as iron, glass, sand, salt, or chemicals. Inhaling unknown substances and burning or hot particulates like glass, metal, and sand can cause serious damage to the respiratory system.

Disadvantages of irradiated cannabis 

Some patients have expressed concerns about the effects of irradiation on medical cannabis.

This often stems from the lack of research which has been conducted on cannabis and the potential impacts of the sterilisation process. While some studies have been done on the effects of irradiation on cannabinoids and terpenes, these make up a relatively small proportion of the compounds found in the plant, of which there are thought to be more than 300. 

At this stage we don’t know what gamma irradiated cannabis might have on these compounds or specific alterations might occur during the sterilisation process. There are also no standard guidelines for the dose of irradiation which should be used, meaning this could vary widely between manufacturers. 

An industry white paper states that 2000 Gys should be sufficient for microbial sterilisation yet some patients claim to have seen certificates of analysis where far higher levels have been used. 

Meanwhile, there are also reports of patients noticing a ‘chemical smell’ in prescribed medical cannabis products. While some patients report experiencing headaches and chest infections, it is not possible to say for sure that this was linked to consumption of irradiated products.

It’s also worth noting that while irradiation has been considered to be safe for use in food processing where products are ingested into the digestive system, we cannot automatically assume that this makes it safe for cannabis which is often vaporised and absorbed directly into the lungs. 

Some of the UK’s leading experts have called for more research to highlight any potential long-term health risks of irradiated cannabis, particularly when administered via vaporisation. 

Advantages of non-irradiated medical cannabis 

Non-irradiated medical cannabis tends to be preferred by consumers who are concerned about potential changes in the chemical composition or flavour profile as a result of irradiation.

This is often the case among those who have been medicating with cannabis for a longer period of time (before legalisation of medical cannabis) and have a good understanding of which products and strains work for their needs. 

Many report that they find non-irradiated products to be of a better quality than those which have undergone irradiation.

Given the lack of research that has been done in this area, some patients may feel safer using products which have used non-radioactive sterilisation, such as e-Beam, or those which have relied on strict manufacturing standards to control contaminants. 

Disadvantages of non-irradiated medical cannabis 

There is a risk that non-irradiated medical cannabis products contain contaminants, including bacteria and fungi, as well as residual heavy metals and pesticides from the growing process.

If you’re someone who has an autoimmune condition, a weakened immune system or are at greater risk of respiratory issues it may be best to avoid these products. 

At the moment in the UK the cost of non-irradiated products tends to be higher than that of irradiated cannabis due to additional expenses incurred during the manufacturing process, higher demand with less competition on the market, and the fact that these products are deemed by some to be of higher quality.

Final thoughts 

Both irradiated and non-irradiated cannabis products can be safe and effective for medical use when produced according to regulatory requirements and subject to rigorous testing. 

It is important that all medical cannabis products come with safety and quality assurance, but equally, that patients feel confident in the medication they are using. 

While irradiation is generally accepted in the industry to ensure producers meet the necessary standard and regulations, it is worth remembering that as the vast majority of cannabis medicines prescribed in the UK are unlicensed medicines, they have not been assessed by the Medicines and Healthcare products Regulatory Agency (MHRA) for safety, quality or efficacy.

Until more research is carried out, the choice between irradiated and non-irradiated cannabis may ultimately depend on individual preference. For this reason, it is crucial to ensure patients are armed with the right knowledge to enable them to make an informed choice when it comes to decisions about their health. 

If you choose to pursue a medical cannabis prescription, Releaf’s team of experts can help answer any concerns you might have about irradiated or non-irradiated cannabis, and you can work with your prescribing clinician to find the product that is best suited to your needs. 

It is important to seek medical advice before starting any new treatments. The patient advisors at Releaf are available to provide expert advice and support. Alternatively, click here to book a consultation with one of our specialist doctors.

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Sarah, a distinguished journalist with over a decade in publishing and communications, now excels in cannabis health and policy journalism in the UK, advocating for informed health decisions through her award-winning work.

Our articles are written by experts and reviewed by medical professionals or compliance specialists. Adhering to stringent sourcing guidelines, we reference peer-reviewed studies and scholarly research. View our editorial policy.

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Further reading

Trust your gut: IBS and medical cannabis

Cannabis has been used as a therapeutic for thousands of years, with evidence of its use in the treatment of gastrointestinal issues dating back centuries. Anecdotal evidence suggests that medical cannabis may be useful in the treatment of Intestinal Bowel Syndrome (IBS), and a growing body of clinical and observational evidence appears to support this potential.

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