Medicinal Cannabis THC Levels in Australia: A Safety Review 2026

Medicinal cannabis with very high THC levels is being regularly prescribed in Australia, raising safety concerns. A new review from Monash University reveals that doctors commonly prescribe products with up to four times the THC concentration tested in clinical trials. This article explores the evidence gap, regulatory challenges, and what patients need to know.

Why High-THC Medicinal Cannabis Is a Concern

THC, or delta-9-tetrahydrocannabinol, is the main psychoactive ingredient in cannabis. In Australia, there is no upper limit for THC concentration in medicinal cannabis products. Category 5 products, which include dried herb and concentrated extracts, range from 13% to 88% THC. However, clinical trials have only tested products containing up to 22% THC.

Professor Suzanne Nielsen from the Monash Addiction Research Centre highlights the mismatch: “When we looked at the randomised control trial evidence, we saw there is a real mismatch between the evidence we have to draw on and the products being prescribed.” This gap means patients may be exposed to unknown risks.

Evidence vs. Practice: A Stark Discrepancy

The review, published in the Drug and Alcohol Review, evaluated studies on medicinal cannabis for various conditions. Only products with up to 22% THC were tested in randomised controlled trials. Yet, Australian prescribers often choose higher-potency products, sometimes exceeding 35% THC.

This table illustrates the gap between what is proven and what is being used. Higher THC doses may increase risks of anxiety, paranoia, and dependency, yet patients are not fully informed.

Regulatory Gaps in Australia

Of more than 1,000 medicinal cannabis products available, only two have undergone pre-market evaluation by the Therapeutic Goods Administration (TGA) for quality, safety, and efficacy. This lack of oversight means most products are prescribed without robust evidence.

What the TGA Should Do

Professor Nielsen suggests the TGA should consider setting THC concentration limits at or below levels naturally occurring in the cannabis plant—about 35%—or even at 22% in line with trial evidence. She also recommends better labelling and health warnings, plus improved screening and monitoring of harms.

Key Takeaways for Patients and Prescribers

• High-THC medicinal cannabis may not be safer or more effective than lower-dose options.
• Only 2 out of 1,000 products have been rigorously evaluated by the TGA.
• Patients should ask about THC content and available evidence before starting treatment.
• Better regulation could reduce potential harms and improve patient outcomes.

Consumer Understanding Is Lacking

It’s unclear how well consumers understand the products they are using. Many may not realise that higher THC levels come with increased risks. Clear labelling and education are essential to help patients make informed decisions.

FAQ

In conclusion, the current practice of prescribing high-THC medicinal cannabis in Australia is not supported by clinical evidence. Regulatory changes, better labelling, and patient education are crucial to ensure safety and efficacy. If you or a loved one are considering medicinal cannabis, consult with a healthcare professional who is aware of these risks.