CBD vs THC: What’s the Difference?

CBD and THC are the most well-known cannabinoids found in hemp and cannabis. They’re often discussed together, but their effects — and legal status — are very different. Knowing how they diverge helps you choose safely and confidently.

The key differences between CBD and THC (including side effects)
Why they act differently in the body
What drug tests look for — CBD vs THC

What’s the difference between THC and CBD?

Both are cannabinoids — plant compounds that interact with your endocannabinoid system (ECS), which helps regulate mood, sleep, appetite, inflammation and more. Over 100 cannabinoids exist; CBD and THC are the most studied.

What is THC?

THC (Δ9-tetrahydrocannabinol) is psychoactive — it can alter perception, mood, coordination and reaction time by directly activating CB1 receptors in the brain. Beyond recreation, THC is being investigated clinically and features in certain cannabis-based medicines.

Read more: Hemp vs Marijuana

What is CBD?

CBD (cannabidiol) is non-intoxicating. Rather than strongly activating CB1 like THC, it modulates ECS signalling and interacts with other targets (e.g., 5-HT1A serotonin receptors). Many people use CBD as a wellness supplement to support balance and recovery.

Complete this one-minute quiz to find products that fit your goals.

1) Chemical structure

CBD and THC share the same molecular formula (C₂₁H₃₀O₂) but differ in atom arrangement. That small structural change dramatically alters how each molecule binds to receptors — and how it feels.

2) Psychoactive effects

THC can make you feel “high.” CBD will not — when you’re using a compliant, well-made product.

In the UK, consumer CBD products must keep controlled cannabinoids to legally permitted trace levels. Reputable brands publish batch Certificates of Analysis (COAs) showing THC is not detected (or below legal trace limits) in the finished product.
Broad-spectrum and isolate CBD are made to be THC-free; full-spectrum includes a wider range of plant compounds and, when sold lawfully in the UK, should still keep THC to non-detectable/trace levels in the finished item.

3) Potential benefits

Neither CBD nor THC is a cure-all. Evidence ranges from early lab work to clinical trials; always speak with a clinician for medical conditions.

CBD (non-intoxicating)

General stress support and mood balance
Sleep quality and wind-down routines
Everyday aches, soreness and recovery
Adjunct support in certain seizure disorders (prescription formats)

Read more: Benefits of CBD

THC (intoxicating; controlled)

Pain, spasticity and nausea in specific settings (e.g., licensed medicines like nabiximols or synthetic THC analogues prescribed for chemotherapy-related nausea)
Appetite stimulation
Potential benefit in certain neurological or palliative contexts under medical supervision

Note: Many effects of THC and CBD are studied both alone and together (the “entourage effect”). Any use of THC in the UK outside prescribed products remains illegal.

4) Side effects & interactions

CBD

Dry mouth, reduced appetite, GI upset
Drowsiness or fatigue in some users
Interactions: CBD can affect drug metabolism (CYP450). If your medicine has a grapefruit warning — or any prescription at all — consult a healthcare professional first.

THC

Impaired coordination, short-term memory issues
Increased heart rate, anxiety or paranoia at higher doses
Red eyes, dry mouth, slower reaction time
Heavy or early-age use has been linked with mental-health risks; avoid operating machinery or driving.

5) Legality (UK focus)

THC: A controlled substance in the UK. Possession/supply without a prescription can lead to prosecution. Some cannabis-based medicines are licensed or available via specialist clinicians.
CBD: Legal to sell as a novel food supplement when derived from approved sources and the final product keeps controlled cannabinoids within legally permitted trace levels. Responsible brands provide COAs and follow FSA guidance.

Read more: CBD Legal Countries

6) Drug testing

Standard screenings target THC metabolites, not CBD.
THC can remain detectable for days to weeks (it’s fat-soluble).
CBD-only products should not trigger a positive test, but risk rises with poor-quality or mislabelled products. To minimise risk, choose broad-spectrum or isolate CBD with a recent third-party COA confirming THC is not detected in the finished product.

Read more: CBD and Drug Tests

FAQ

Is CBD “better” than THC?

They’re different tools. CBD is non-intoxicating and widely used for wellness. THC is intoxicating and tightly controlled, with specific medical applications under prescription.

What’s better for pain — CBD or THC?

It depends on the type of pain and individual response. CBD may support inflammatory balance and recovery; THC has recognised analgesic effects but is controlled. Medical guidance is recommended for persistent pain.

Is there THC in CBD oil?

UK consumer CBD should keep controlled cannabinoids to non-detectable/trace legal levels. If you want to avoid THC entirely, pick broad-spectrum or isolate and verify the COA.

Will CBD make me fail a drug test?

Drug tests screen for THC metabolites. Quality CBD-only products should not cause a positive, but contaminated/mislabelled items can. Choose products with third-party COAs confirming no detectable THC in the finished product.

Key takeaways

THC = psychoactive, controlled; CBD = non-intoxicating, sold as a supplement within strict rules.
Choose products with transparent lab reports (COAs) and responsible manufacturing.
Talk to a clinician if you take medicines, have a condition, are pregnant/breastfeeding, or are considering medical cannabis.

Shop CBD