CBD vs THC: the difference explained simply

CBD vs THC at a glance

The table shows the most important differences between THC and CBD at a glance. The sections below explain each point in more detail.

What is THC?

THC is the most important psychoactive ingredient of the cannabis plant and has been at the centre of cannabis research for decades. In medicine, THC is used as part of flowers and extracts, as the pure substance dronabinol and in the form of chemically related substances such as nabilone.

THC binds to the cannabinoid receptors CB1 and CB2 and partly activates them. Experts call this a partial agonist. According to pharmacological research, how strongly a person reacts depends on how many receptors are present, how well they pass on signals and how many of the body's own cannabinoids are being released at the time. This explains why the same amount has such different effects in different people.

Typical effects are relaxation, altered perception, increased appetite and, in some people, anxiety or restlessness. After inhaling, the effect starts within minutes and peaks after 15 to 30 minutes. After swallowing, it only starts after 30 to 90 minutes and lasts up to 12 hours.

What is CBD?

After THC, CBD is the best-known cannabinoid. It does not cause a high, but it is not without effect. In the laboratory, CBD tends to act as an antagonist at the CB1 and CB2 receptors: with unexpectedly high potency, it blocks the effects of other substances that activate these receptors. CBD also acts on other targets in the body.

CBD has been authorised as a medicine in the EU since 19 September 2019, for narrowly defined uses: for the rare forms of epilepsy Lennox-Gastaut syndrome and Dravet syndrome in addition to the active ingredient clobazam and, without this condition, for tuberous sclerosis complex, in each case from the age of two. For many other complaints that CBD products are advertised for, there is no solid evidence.

In 2025, the Senate Commission on Food Safety of the German Research Foundation (DFG) concluded that foods and food supplements containing CBD offer no scientifically proven health benefits and may pose a health risk.

How do THC and CBD work in the body?

THC and CBD act via the endocannabinoid system, the body's own signalling system made up of messenger substances and receptors. The CB1 receptor is found mainly in the nervous system, the CB2 receptor mainly in cells of the immune system. The system is involved in pain perception, appetite, mood, memory and sleep, among other things.

THC mimics the body's own messenger substances and mainly activates CB1 in the brain. This causes the high and many side effects. CBD barely activates CB1. Whether the blocking effect measured in the laboratory plays a role in humans at usual amounts is another question, and studies have tested it specifically, as the next section shows.

With regular THC use, the system adapts: the effect wears off and tolerance develops. For treatment, this means that more THC does not bring more effect in the long run.

Does CBD make THC safer?

No, not according to current studies at the ratios usual in products. For a long time it was assumed that CBD buffers the unpleasant effects of THC. A randomised double-blind study by King's College London tested this in 2023 with 46 healthy adults who rarely used cannabis.

Participants inhaled vaporized cannabis with the same amount of THC and different amounts of CBD, at ratios from 0:1 to 3:1. THC impaired delayed recall of words and temporarily caused psychosis-like symptoms. None of the CBD amounts weakened these effects, nor any of the other effects measured.

The study has limits you should know about: it looked at healthy people with little cannabis experience, single doses and short-term effects. It does not answer whether CBD works differently with long-term use, in patients or at much higher ratios. But it offers no support for the assumption that CBD makes THC safe.

This does not mean the ratio is irrelevant. It does mean that a CBD share is no licence for high THC amounts. What matters remains the amount of THC, how often it is used and a medically supervised adjustment.

How long do THC and CBD last?

How quickly and for how long THC works depends mainly on whether it is inhaled or swallowed. A pharmacological review gives typical time spans for this. For CBD there is less reliable data on the time course, because it does not produce a noticeable high from which the onset could be read.

When swallowed, only a small part of the cannabinoids reaches the bloodstream, and this part varies greatly from person to person. The literature gives an oral bioavailability of 6 to 20 per cent for THC, because stomach acid and breakdown in the gut and liver intercept a large share. This is why amounts cannot be transferred one to one between inhalation and oil.

What are the side effects of THC and CBD?

THC and CBD have different side effect profiles. With THC, short-term effects on the brain and circulation are in the foreground; with CBD, effects on the liver and on how other medicines are broken down. An overview of all side effects of medical cannabis can be found in Medical cannabis side effects.

• THC in the short term: tiredness, dizziness, dry mouth, racing heart, problems with concentration and memory, at higher amounts anxiety and panic.
• THC in the long term: risk of addiction and psychosis. A European study found a roughly threefold higher risk of a psychotic disorder with daily use and a nearly fivefold higher risk with daily use of cannabis containing at least 10 per cent THC.
• CBD: according to the DFG commission, liver damage has already been observed at higher daily amounts over four weeks. CBD inhibits liver enzymes that break down many medicines and can thus change their levels.
• CBD in pregnancy, breastfeeding and with medicines: the DFG commission advises pregnant and breastfeeding women and people taking prescription medicines against CBD products.
• CBD and reproduction: the European Food Safety Authority (EFSA) points to clear effects on reproduction in animal studies, whose relevance for humans has yet to be clarified.

What happens if you take too much THC?

According to a pharmacological review, the most important acute consequences of too much THC are anxiety and panic attacks, a fast pulse and fluctuations in blood pressure. Many people also experience dizziness, nausea or the feeling of being beside themselves. With oil and capsules this often only happens hours after taking them.

In that case: sit or lie down, drink water, take nothing more, do not drive and tell someone you trust. In case of chest pain, shortness of breath, impaired consciousness, a seizure or ongoing panic, call the emergency number 112. If a child has taken something, call a poison control centre (Giftnotruf) or 112 immediately.

Why interactions matter with CBD

CBD is broken down in the liver by the same enzymes as many medicines, for example from the cytochrome P450 system. It can inhibit these enzymes. The level of another medicine may then rise, and its side effects increase.

If you take medicines regularly, do not take CBD without first talking to your doctor or pharmacist. You can also ask your pharmacy (Apotheke) about possible interactions.

THC-dominant, balanced, CBD-dominant: what does the ratio mean?

Medical cannabis products are classified by their ratio of THC to CBD. Experts speak of the chemovar, meaning the chemical profile of a strain, rather than indica or sativa.

• THC-dominant: a lot of THC, hardly any CBD. The psychoactive effect is in the foreground.
• Balanced: similar amounts of THC and CBD.
• CBD-dominant: mostly CBD, little THC. Less intoxicating, but not automatically free of side effects.

Which ratio is suitable for whom?

Which ratio is suitable depends on symptoms, previous experience, tolerability and risks, and it is a medical decision. International consensus recommendations on pain treatment, developed by 20 experts from nine countries, usually start with CBD-predominant products and add THC only gradually and cautiously.

Besides THC and CBD, other ingredients shape the profile, such as terpenes. Whether they change the effect in humans is unclear. Why the terms indica and sativa say little about these profiles is explained in Indica, sativa, hybrid.

Particular caution is needed with high THC contents: more THC is not better.

What do the THC and CBD figures on the label mean?

The label of medical flowers shows the THC and CBD content in per cent. In the plant, both substances are mainly present as acids, THCA and CBDA, which are not intoxicating themselves. Only heating, for example in a vaporizer, turns them into THC and CBD. This process is called decarboxylation.

In a laboratory study, more than 90 per cent of the THC in the flowers tested was present as THCA. Temperature-controlled vaporizers converted at least 97 per cent of it into THC. Figures for total THC therefore count THC and THCA together.

For you, this means: the percentage on the label describes the active ingredient content of the flower, not the amount that reaches your body. How much of it takes effect depends on the device, how you use it and your body. How vaporizing works is explained in Vaporizing cannabis instead of smoking.

Are there other important cannabinoids besides THC and CBD?

Yes, the cannabis plant produces many other cannabinoids, usually in much smaller amounts. For most of them, the effect in humans has hardly been studied.

• THCV (tetrahydrocannabivarin): in the laboratory it acts as a partial activator at the CB2 receptor and tends to block CB1, but in animal studies it also activates it at higher amounts.
• CBN (cannabinol): forms, among other things, when THC ages in the air. A higher CBN share is therefore also a sign of older or poorly stored product.
• CBG (cannabigerol): a precursor from which the plant forms other cannabinoids. Clinical data in humans is largely lacking.

CBD products from chemists and online shops

CBD oils, capsules or gummies from chemists (Drogerie) and online shops are not medicines. In the EU they count as novel foods and would need novel food authorisation. According to the DFG commission, no CBD product has received such authorisation so far, yet many are on the market.

In 2022, EFSA concluded that the safety of CBD as a food cannot currently be established. Data is missing on the liver, the gastrointestinal tract, the hormone system, the nervous system and mental health.

Quality also varies. A study in the journal JAMA analysed 84 CBD products bought online in 2017. Only 31 per cent contained roughly the stated amount of CBD, and some products also contained THC. According to the DFG commission, many products also contain more CBD per stated serving than is considered acceptable for food.

THC, CBD and drug tests: what you should know

With regular use, THC and its breakdown products remain detectable much longer than the noticeable effect lasts. A positive test therefore does not automatically mean that someone is currently impaired, and vice versa. How long THC can be detected in blood, urine or saliva is explained in How long THC stays detectable.

CBD itself is not an intoxicant. But because CBD products from shops can contain THC, a positive THC test after using them cannot be ruled out. Anyone who may face tests at work or on the road should know this.

THC and CBD on German roads

Under § 24a of the German Road Traffic Act (StVG), anyone driving a motor vehicle with 3.5 ng/ml or more of THC in their blood serum commits an administrative offence. There is no separate limit for CBD.

The rule does not apply if the THC comes from taking a medicine as intended that was prescribed for a specific medical condition. Even then, you may only drive if you are definitely fit to drive. What this means in practice is explained in the guide Driving with a cannabis prescription.

Five myths about THC and CBD

Many claims circulate about THC and CBD. These five do not stand up to scrutiny.

• “CBD cancels out the effect of THC.” In the 2023 double-blind study, it did not at usual ratios.
• “CBD products never contain THC.” In the JAMA study, THC was found in some products bought online.
• “CBD is a natural remedy without side effects.” The DFG commission describes effects on the liver and interactions with medicines.
• “More THC means a better effect.” With rising amount and frequency, side effects, tolerance and the risk of psychosis increase.
• “What is legal has also been tested.” CBD foods have no novel food authorisation so far, and their quality is not controlled as it is for medicines.

What to discuss with your doctor

Whether a THC-predominant, balanced or CBD-predominant product is suitable can only be clarified in a consultation. These points belong on the table, even if they feel uncomfortable.

• Previous experience with cannabis, including recreational cannabis, and how well you tolerated it.
• Mental illness in your own or your family's history, especially psychosis.
• All medicines and food supplements, including CBD products bought over the counter.
• Pregnancy, plans to have children or breastfeeding.
• Your job, driving licence and possible drug tests in everyday life.

THC and CBD under German law

Since 1 April 2024, cannabis containing THC for medical purposes has been regulated in Germany by the Medical Cannabis Act (MedCanG). It is only prescribed by a doctor and dispensed by pharmacies. Recreational cannabis is governed by the rules of the Consumer Cannabis Act (KCanG).

CBD is not an intoxicant. The authorised CBD medicine is only available on prescription. CBD foods and food supplements have not yet been authorised as novel food in the EU. Health claims must not be made for them.

Frequently asked questions