THC vs CBD — Which Is Right for Your Condition?
THC vs CBD explained for UK medical cannabis patients. Learn the medical uses of each cannabinoid, the entourage effect, UK legal limits, and how to choose by condition.
Quick Navigation
What Is THC?
Tetrahydrocannabinol (THC) is the primary psychoactive compound in cannabis. It binds strongly to CB1 receptors in the brain and nervous system, producing the characteristic "high" associated with recreational cannabis use. In a medical context, however, THC's ability to modulate pain signals, reduce nausea, stimulate appetite, and promote sleep makes it a clinically valuable compound. In the UK, THC-containing products can only be obtained via a prescription from a specialist doctor — they are Schedule 2 controlled drugs under the Misuse of Drugs Regulations 2001.
Common THC-dominant medical preparations include dried cannabis flower (for vaporisation), THC-rich oils, and capsules. Potency is typically expressed as a percentage: a product labelled "T22" contains approximately 22% THC by weight.
What Is CBD?
Cannabidiol (CBD) is the second most prominent cannabinoid and is entirely non-psychoactive. It works through multiple mechanisms — partial agonism at CB1/CB2 receptors, antagonism at GPR55, modulation of serotonin (5-HT1A) receptors, and inhibition of adenosine reuptake — producing anti-inflammatory, anxiolytic, anticonvulsant, and neuroprotective effects without intoxication. In the UK, CBD products derived from industrial hemp (containing less than 0.2% THC) are legal as food supplements, but pharmaceutical-grade CBD (such as Epidyolex for epilepsy) is a licensed medicine.
High-CBD medical cannabis preparations are often labelled with their CBD percentage followed by THC: a "C20/T1" product contains 20% CBD and 1% THC. These are available via prescription from cannabis clinics for patients who need the full-spectrum medical effect without significant psychoactivity.
Medical Uses of THC
- Chronic pain — particularly neuropathic, cancer-related, and central sensitisation pain
- Muscle spasticity — as in multiple sclerosis (Sativex, a 1:1 THC:CBD spray, is licensed for MS spasticity)
- Nausea and vomiting — especially chemotherapy-induced nausea (Nabilone, a synthetic THC, is licensed for this)
- Sleep disorders — THC reduces sleep onset latency and increases slow-wave sleep
- Appetite stimulation — in cancer cachexia, HIV-related wasting, and anorexia
- PTSD — reducing nightmares and hyperarousal via CB1 modulation of fear memory extinction
Medical Uses of CBD
- Epilepsy — Epidyolex (pharmaceutical CBD) is licensed in the UK for Dravet syndrome and Lennox-Gastaut syndrome
- Anxiety disorders — multiple trials support CBD's anxiolytic effects at doses of 150–300mg
- Inflammation — arthritis, inflammatory bowel disease, and autoimmune conditions
- Neuroprotection — emerging research in Parkinson's disease, Alzheimer's disease, and traumatic brain injury
- Sleep quality — lower doses (25–75mg) may reduce anxiety-driven insomnia without sedation
- Addiction — evidence suggests CBD reduces cravings for opioids and tobacco
The Entourage Effect — Why Both Together Often Works Best
The "entourage effect" describes the phenomenon whereby cannabinoids, terpenes, and other plant compounds work synergistically — producing effects greater than either component alone. A landmark 2011 paper by Dr Ethan Russo proposed that CBD modulates THC's psychoactive and adverse effects (reducing anxiety, paranoia, and memory impairment) whilst enhancing its analgesic and anti-inflammatory properties. This explains why whole-plant or broad-spectrum preparations often outperform isolates in clinical settings.
In practice, many UK specialists prescribe a balanced THC:CBD preparation (1:1 or 1:2 ratio) as a starting point, titrating the ratio based on patient response. Explore our strain profiles to see the cannabinoid ratios of commonly prescribed cultivars.
UK Legal Limits
Under UK law, cannabis products fall into three categories:
- Prescription CBMPs (Schedule 2): any THC level, requires specialist prescription — available through licensed cannabis clinics
- CBD food supplements (legal, no prescription): must contain no more than 1mg THC per container (effectively <0.2% THC)
- Recreational cannabis (Class B): illegal regardless of THC content
Patients sometimes confuse over-the-counter CBD products with prescription medical cannabis. High-street CBD is legal but typically underdosed and unregulated for medical use. For meaningful therapeutic benefit, prescription-grade CBMPs dispensed by licensed pharmacies are required.
Choosing by Condition — A Practical Guide
| Condition | Recommended Ratio | Notes |
|---|---|---|
| Neuropathic pain | THC-dominant (T20+) or balanced 1:1 | Evening use; start low |
| Fibromyalgia | Balanced THC:CBD or high-CBD | Daytime CBD + evening THC |
| Anxiety | High-CBD (>15% CBD, <1% THC) | High THC can worsen anxiety |
| Epilepsy | High-CBD (pharmaceutical grade) | Epidyolex or prescription CBMP |
| PTSD | Balanced or THC-dominant (evening) | CBD for daytime, THC for nightmares |
| Insomnia | Indica-dominant THC or balanced | Avoid sativa at night |
| MS spasticity | Balanced THC:CBD (Sativex equivalent) | Licensed treatment available |
| Arthritis inflammation | High-CBD with low THC | CBD topicals may complement |
Products Available in the UK
UK patients can access a growing range of prescription cannabis products through licensed pharmacies. Browse our product catalogue to compare flower, oils, and capsules by cannabinoid ratio, manufacturer, and price. Key product types include:
- Dried flower (for use in a medical vaporiser) — fastest onset, highest bioavailability
- Oils and tinctures — slower onset, longer duration, easier to dose precisely
- Capsules — consistent dosing, very slow onset (2–4 hours)
Use LeafMe to compare prices across UK cannabis clinics and find the most cost-effective product for your condition.