Understanding Medical Cannabis Strength: A Guide for Healthcare Professionals

Published: July 2025

When prescribing medical cannabis, it’s essential to understand and accurately communicate the “strength” of the product. However, the lack of standardisation in the way cannabis strength is represented can lead to confusion, complicating safe prescribing, patient education, and effective transitions between products.¹ In this article, we will simplify the key concepts used to describe medical cannabis strength and highlight how these terms impact clinical practice.

Methods of Describing Medical Cannabis Strength

Current methods for expressing medical cannabis strength are determined by the amount of the two primary cannabinoids, CBD (cannabidiol) and THC (tetrahydrocannabinol) in a product. THC is considered the primary psychoactive component, whilst CBD is thought to modulate THC’s effects.² The dose at which THC’s psychoactive properties become clinically apparent is generally regarded to be 5 mg.³

Medical cannabis strength can be described in different ways, each with its unique meaning:

Total Cannabinoid Content (mg)

This measurement describes the actual amount of THC and/or CBD per unit, such as per capsule, gummy, or spray. For example, a capsule might contain 5 mg of THC and 5 mg of CBD. Total cannabinoid content is the most clinically meaningful way to describe cannabis product strength and aligns with the dosing nomenclature used for other medications. For example, a drug may be prescribed with a specific dose in milligrams (such as 5 mg of morphine), and cannabis dosing follows this same principle.

Cannabinoid Ratios (e.g. CBD:THC)

This ratio describes the balance of two primary cannabinoids in a product. For example, a product with a 20:1 ratio has 20 parts CBD for every 1 part THC. The ratio can help you quickly compare products but doesn’t indicate the actual dose of THC or CBD. For instance, both a 1:1 product containing 2.5 mg of each cannabinoid and one containing 25 mg of each would have the same ratio but differ in dose. Therefore, clinical decisions must reference the exact quantities or percentages of the cannabinoids, not just the ratio.

Potency (%)

Potency refers to the percentage of a product’s weight that consists of THC or CBD. For instance, a product labeled as 15% THC means each gram of dried flower contains 150 mg of THC. Potency is often used to describe the strength of products like oils, tinctures, and flower, helping to compare their strength quickly. This is especially helpful when assessing products used for inhalation or topical application.

Patient tolerance - a key factor affecting dosage and strength

Tolerance to cannabis varies significantly from patient to patient.⁴ Cannabis-naïve patients (first-time users or those with limited experience) are much more sensitive to cannabinoids.⁴ Therefore, it’s essential to start with a low dose and gradually increase as needed.¹ Conversely, experienced users may require higher doses to achieve the desired effect and may benefit from short breaks in therapy to reduce the likelihood of developing tolerance.⁴ Prescribers should always consider the patient's history when determining dosage.¹

TGA Categorisation

In Australia, the Therapeutic Goods Administration (TGA) classifies medical cannabis products based on their CBD content.⁵ This classification can be confusing as it reflects only the proportion of CBD in the product, not its THC or other cannabinoid content. For example, products in the "CBD dominant" category may still contain significant amounts of THC, which could have psychoactive effects.

Standardising Cannabis Dosing

Unlike opioids, where doses are standardised using measures such as oral morphine equivalents (OME), medical cannabis currently lacks a universally accepted standard dosing unit. Researchers have proposed using THC content as a common measure, such as defining a “standard THC unit” as 5 mg of THC⁶, which is considered a typical psychoactive dose.³ However, this concept is not yet universally adopted, as cannabis contains multiple active compounds, and individual factors (such as patient tolerance) play a significant role in how patients respond to cannabis.⁶

Clinical Implications and Best Practices

Healthcare professionals should focus on the actual quantities of THC and CBD when determining dosages. This ensures safe and effective prescribing.

Summary

The strength of medical cannabis is described in multiple ways - through ratios, potency percentages, and total milligrams - making it vital for healthcare professionals to understand the clinical implications of each. To ensure accurate dosing and patient safety, always refer to the total amount of THC and CBD in the product, and consider patient factors such as experience and tolerance. As the medical cannabis market evolves, the need for clearer and more standardised labeling becomes increasingly important for effective prescribing and patient education.

By adhering to these best practices, healthcare professionals can reduce medication errors, improve patient outcomes, and promote best practices in prescribing and dispensing medical cannabis.