For first-time medical cannabis patients, knowledge is power. Understanding what cannabis is and how it affects our bodies will help you get the right treatment. And one of the first questions you may ask is: What is THC?
Tetrahydrocannabinol (THC) is a key active ingredient in medical cannabis. It’s a compound called a cannabinoid. There are over a hundred other cannabinoids found in the plant, THC is responsible for the psychoactive properties.
Read on for the lowdown on THC and how it’s used in medicine.
What Is THC?

The cannabis plant contains dozens of chemically active compounds called cannabinoids. Each of these cannabinoids interacts with receptors throughout our body, including our brain, nervous system, and immune system.
THC may be the best known cannabinoid, and it was the first to be discovered in 1964. Famous for its euphoric and psychoactive properties, it's responsible for the signature “high” associated with cannabis use.
It’s also one of the most common cannabinoids. Along with CBD, THC makes up the majority of active cannabinoids in most strains of cannabis. Other cannabinoids (like CBN and CBG) occur in much smaller quantities.
THC vs CBD: How Are They Different?
THC and CBD often occur together in the cannabis plant in varying quantities. Some strains may have lots of THC and minimal CBD, or vice versa, while others will have an equal amount of both.
The ratios of THC to CBD matter because each cannabinoid affects our bodies and brains differently. While THC is a psychoactive compound affecting our mind and perception, CBD has a more subtle effect on the body. CBD is not psychoactive. It still has medicinal effects and is often prescribed for pain, inflammation, and anxiety.
Understanding the difference between THC and CBD is helpful when understanding your prescription and the different options available. Depending on your condition, symptoms, and lifestyle, you may benefit from a different combination of THC and CBD.
How Does THC Work?
THC affects our bodies because it can bind to receptors in our endocannabinoid system (ECS). These receptors are designed to bind to endocannabinoids, which are chemicals that occur naturally in our body and have similar structures to cannabinoids.
When we consume THC, it bonds to specific receptors called CB1 receptors. These exist primarily in our brain and nervous system but also other organs such as the gastrointestinal system.
So, what is it like to use THC?
It can cause various effects on our brain and body, from euphoria and pain reduction to paranoia and increased appetite. The dose of THC, along with interactions with other cannabinoids like CBD, will alter the effects.
Research on the ECS is relatively new, and there’s a lot we still don’t know. For example, CBD doesn’t bind directly to receptors like CB1, but it does interact with the ECS in a way we don’t yet understand.
What Is THC Prescribed for?
In Australia, doctors can prescribe medical cannabis for any condition if it benefits the patient. There is no restricted list of qualifying conditions that are approved for treatment with cannabis, which is the case in other countries.
Instead, they work with a doctor to discuss their current health concerns, medical history, and past treatment options. Then, the doctor will determine the best course of action, including a possible prescription for THC-containing medical cannabis.
Medical cannabis products in Australia are categorised based on their THC and CBD content. Most common medical cannabis products contain a combination of THC, CBD, and sometimes other cannabinoids.
Working with a doctor to determine the right product, dose, and strain for your condition and needs is essential. For example, a high-THC product may work well for chronic pain in one patient but not another. Equally, a high-CBD product may be more suitable in some circumstances, depending on the patient and their symptoms.
Is THC Safe?
Medicinal cannabis containing THC is considered a “relatively safe drug,” by the TGA, by the Australian Journal of General Practice, and other trusted organisations. Over consumption of THC-rich cannabis is extremely rare, with the most common adverse side effects being dizziness, anxiety, and a racing heart.
THC is classified as a Schedule 8 medicine in Australia and can be prescribed by doctors under the TGA Special Access Scheme. This means that while medicinal cannabis hasn’t been approved for general use, doctors can request access to prescribe it if they believe a patient will benefit and other treatments have been tried.
However, there are some circumstances where THC is not recommended. In particular, it’s not recommended that children or teenagers use THC. Additionally, if a patient has a family history of psychosis, THC could make them more vulnerable to experiencing psychosis or schizophrenia.
Is THC Right For You?
Let's summarise what we’ve learned after asking, “What is THC?”
THC is one of the main active compounds in medical cannabis, responsible for many of its effects. But, its effects depend on the dose, method of delivery, and your genetics, conditions, and needs.
To find out if THC is right for you, book a consultation with an expert alternaleaf doctor. We’ll support you in finding the right treatment for you.