What a THC:CBD ratio describes
A THC:CBD ratio compares the amount of THC with the amount of CBD in a product. A 1:1 preparation contains roughly equal amounts. A 20:1 preparation contains much more THC than CBD.
The ratio does not reveal the dose. One milligram of THC with one milligram of CBD and ten milligrams of each are both 1:1, but they are not equivalent exposures.
Read the amount as well as the ratio
For an oil, the useful figures are usually milligrams of THC and CBD per millilitre and the prescribed volume. For flower, labels usually report percentages by weight. Route also changes onset, duration and how consistently a dose can be measured.
A useful comparison therefore includes:
- THC per dose
- CBD per dose
- oil, flower, capsule or spray
- prescribed volume or amount
- timing and frequency
Why balanced products are studied
THC and CBD have different pharmacology. Controlled laboratory studies have tested whether CBD changes some acute effects of THC, but results depend on dose, timing and route. They do not establish that every balanced product is less impairing or better tolerated.
Nabiximols is an approximately balanced THC:CBD medicine licensed for MS spasticity in defined circumstances. Its evidence belongs to that standardised oromucosal spray, not to every product with a similar ratio.
Purified CBD medicines for particular severe epilepsies provide another example. Their evidence comes from a defined dose and formulation; “CBD-dominant” on a different product is not the same intervention.
Ratio language on prescriptions
“THC-dominant”, “balanced” and “CBD-dominant” are useful shorthand, but the boundaries are not universal. Two pharmacies or producers may use the same term for different concentrations. The dispensing label and formulation are the source of the actual numbers.
What the ratio does not predict
A ratio cannot predict an individual response, side effects or driving impairment. It also says nothing about terpenes, minor cannabinoids or batch variation. Those details may describe the product, but they do not replace the absolute THC and CBD dose.
Read next
Sources
- NICE. Cannabis-based medicinal products, guideline NG144. NICE guidance
- Bhattacharyya S, et al. Opposite effects of delta-9-tetrahydrocannabinol and cannabidiol on human brain function and psychopathology. Neuropsychopharmacology. 2010. Study record
- Englund A, et al. Cannabidiol inhibits THC-elicited paranoid symptoms and hippocampal-dependent memory impairment. Journal of Psychopharmacology. 2013. Study record
- Electronic Medicines Compendium. Sativex Summary of Product Characteristics. Medicine record
- Electronic Medicines Compendium. Epidyolex Summary of Product Characteristics. Medicine record
