Overview

Delta-9-tetrahydrocannabinol (THC) is a cannabinoid that comes from Cannabis sativa (cannabis). It is the main psychoactive chemical in cannabis, which means it causes brain-altering effects and can make you feel “high.” There is interest in using THC for many reasons, but its benefits for most uses are not well defined. Common side effects include problems thinking clearly, dizziness, sleepiness, hallucinations, intense feelings, paranoia, and fear. Serious side effects are less common and include dependence and withdrawal, changes in your blood pressure, psychotic-like behavior, and a condition called cannabinoid hyperemesis syndrome (CHS). Before using THC, make sure to tell your health care provider about any health conditions you have or medicines you are taking.

Uses

What is delta-9-tetrahydrocannabinol (THC) used for?

Delta-9-tetrahydrocannabinol (THC) is used recreationally to improve mood or feel “high.” It is also used for some health reasons, but its benefits are not well defined. Some common reasons for using THC include the following.

• For mental health problems, including anxiety, depression, and posttraumatic stress disorder (PTSD)
• For nausea or vomiting from various causes
• For nerve or muscle pain
• To help manage stress
• To increase appetite, especially in people with serious illness, such as cancer or AIDS

If you are having symptoms of a mental health problem, do not try to treat these symptoms on your own. Talk to your health care provider about your treatment options. If you are already taking medicine for a mental health problem, talk to your health care provider before using THC. THC can interact with many medicines.

A synthetic (made in a lab) form of THC is available as a prescription medicine. See Dronabinol for more information.

Note: THC is not approved by the FDA for any use. The FDA also does not consider THC to be a legal dietary ingredient in the U.S. It is a schedule I controlled substance, which means that it does not have an acceptable medical use and has a high risk for misuse. Learn more about the legal status of THC here.

Many U.S. states have legalized recreational cannabis and THC or allow their use for specific medical purposes (“medical marijuana”). Learn more about the legal status of THC and cannabis in each state here.

How does THC work (mechanism of action)?

Delta-9-tetrahydrocannabinol (THC) is a cannabinoid found in the Cannabis sativa plant. Cannabis contains over 100 different cannabinoids. THC, which is also known as delta-9-THC, is the main psychoactive cannabinoid in cannabis. This means that it causes brain-altering effects that can make you feel “high.”

Due to its effects on the brain, many people use THC to improve their mood or manage stress or mental health problems. But the benefits of THC for any mental health condition are unclear, and there is some concern that THC may worsen certain health problems, such as depression or psychosis.

A prescription form of THC, called dronabinol, has been approved in the U.S. for AIDS-related wasting syndrome and nausea or vomiting caused by chemotherapy. This prescription medicine is different from the THC products that can be purchased in some states. Nonprescription products have not been tested to confirm that they contain the ingredients or the amounts stated on their labels, and these products should not be used to replace treatment with prescription dronabinol.

Many people who use THC, or cannabis products that contain THC, report improvement in various symptoms, including pain, nausea, and stress. A small number of studies also show that specific products that contain a standardized amount of THC and other cannabinoids may be helpful for certain uses. But very few studies have evaluated THC on its own, and using high doses of pure THC may cause serious side effects.

Pure THC is removed from cannabis so that it can be given in specific doses. This is very different from using cannabis, which naturally contains many different chemicals in different amounts. Other chemicals in cannabis have effects on the body and brain. These chemicals may also interact with THC, changing its effects in the body. As a result, the effects of cannabis vary depending on how much of each chemical is found in the specific batch you are using.

How should I store THC?

You should store THC according to the product label. Most herbal products should be kept in a cool, dry location that is out of the reach of children and pets and not in direct sunlight.

Side Effects

What are the most common side effects of THC?

The most common side effects of THC are listed below. These side effects may vary depending on the dose or the specific product you are using. Tell your health care provider if you have any of these side effects that bother you.

• Abnormal thinking
• Cannabinoid hyperemesis syndrome (see below)
• Dizziness
• Feelings of intense happiness or joy
• Hallucinations (see below)
• Paranoia or fear
• Sleepiness

There may be other side effects of THC that are not listed here. Contact your health care provider if you think you are having a side effect of a supplement. In the U.S., you can report side effects to the FDA at www.safetyreporting.hhs.gov or by calling 888-SAFEFOOD (888-723-3366). In Canada, you can report side effects to Health Canada at www.health.gc.ca/medeffect or by calling 866-234-2345.

What are the serious side effects of THC?

While less common, the most serious side effects of THC are described below, along with what to do if they happen.

Severe Allergic Reactions. THC may cause allergic reactions, which can be serious. Stop using THC and get help right away if you have any of the following symptoms of a serious allergic reaction.

• Breathing problems or wheezing
• Racing heart
• Fever or general ill feeling
• Swollen lymph nodes
• Swelling of the face, lips, mouth, tongue, or throat
• Trouble swallowing or throat tightness
• Itching or skin rash
• Bumps on the skin called hives that can be red, pink, white, or brown depending on your skin tone
• Nausea or vomiting
• Dizziness, feeling lightheaded, or fainting
• Stomach cramps
• Joint pain

Problems Thinking Clearly. THC can change your mental function and affect your ability to think clearly. Tell your health care provider if you notice any of the following symptoms while using THC.

• Confusion
• Increased sleepiness
• Trouble remembering things
• Unable to concentrate

Cannabinoid Hyperemesis Syndrome.Some people who use THC, cannabis, or other cannabinoids may develop a condition called cannabinoid hyperemesis syndrome (CHS). This condition can happen at any time while using THC and may be more likely in people who have regularly used it for more than a year. CHS causes severe nausea, vomiting, and stomach pain. This can lead to dehydration and changes in electrolyte levels that can be life-threatening. If you have severe nausea or vomiting that does not go away, seek medical help right away. If you think you may have CHS, speak with your health care provider. Stopping all use of THC, cannabis, or other cannabinoids is the only known cure for CHS.

Dependence and Withdrawal Reactions.Some people who use THC may develop physical dependence, which means your body comes to rely on it. This risk may be higher in people who use high doses of THC regularly for multiple months. If you stop THC suddenly, it could lead to withdrawal symptoms. If you have been using THC regularly for a while, do not stop using it abruptly. Your health care provider may be able to help you stop THC in a way that will reduce the risk of withdrawal reactions. Speak with your health care provider if you have any of the following symptoms of THC withdrawal.

• Headaches
• Sweating
• Nausea, vomiting, or stomach pain
• Irritability, anger, or aggression
• Nervousness or anxiety
• Sleep problems or restlessness
• Changes in appetite or weight
• Depression or low mood

Hallucinations or Psychotic-Like Behaviors. THC may cause hallucinations or psychotic-like behaviors. This risk may be higher in people who use high doses of THC or people who also use street drugs. Tell your health care provider right away if you have any of the following symptoms or have been told by others you have these symptoms.

• Hearing, seeing, smelling, tasting, or otherwise perceiving things that others do not
• Delusional thoughts, such as false beliefs that you are being controlled
• Disorganized thoughts, such as jumping between topics or having a hard time focusing
• Sudden decline in self-care, such as personal hygiene or academic/work performance
• Aggressive behavior

Changes in Blood Pressure.THC can raise or lower your blood pressure. People with heart problems and older people (especially those with dementia) are more likely to have changes in blood pressure. This can increase the risk of falling. Tell your health care provider if you have any of the following signs or symptoms of blood pressure changes while using THC.

• Headaches
• Vision problems
• Dizziness
• Lightheadedness
• Fainting
• Fast heartbeat

Precautions

Who should not use THC?

Allergies to Ingredients. People who are allergic to any of the following should not use THC.

• Delta-9-tetrahydrocannabinol
• Delta-9-THC
• Tetrahydrocannabinol
• THC
• Any of the ingredients in the specific product

Ask your health care provider if you are not sure what ingredients are in a THC product.

What should I know about THC before using it?

The U.S. federal government does not consider THC to be a legal ingredient. It is a schedule I controlled substance, which means that it does not have any approved medical uses and is at high risk for misuse. Some U.S. states have legalized cannabis and THC or allow their use for specific medical purposes (“medical marijuana”). THC products are available for purchase at registered businesses in these states. These products are not regulated and have not been tested to confirm that they contain the ingredients stated on their labels.

Using THC will cause a drug test (urine or blood) for cannabis or marijuana to come back positive. Talk to your health care provider if you have concerns.

THC is a controlled substance because it can be misused. If you will store THC at home, store it in a safe place.

Keep THC out of the reach of children and animals. Even small amounts of THC can cause serious health problems in children. If your child takes any products that contain THC, get medical help right away. THC can also be toxic to pets, including cats and dogs. If your pet eats a product that contains THC, call your vet, emergency animal clinic, or animal poison control center right away.

THC can affect your alertness or coordination. Do not drive or do other activities that require alertness or coordination until you know how THC affects you.

People who are under the age of 18 or over the age of 65 can be at greater risk for some side effects from THC. Talk to your health care provider about your risks if you are in either of these age groups.

If you use THC on a regular basis, do not stop using it abruptly. Stopping too quickly may cause serious side effects. See the Side Effects section for more details.

THC is available in many forms, including edibles (foods), gummies, liquid extracts, tea, and more. It is also inhaled by smoking or vaping, and it is available in patches, creams, and other products that are applied to the skin. Your body may respond differently to THC when it is taken by mouth or inhaled. It is not clear if THC can be absorbed into the body through the skin.

THC comes from the Cannabis sativa plant. This plant is a phytoremediator, which means that it is able to pull toxins and heavy metals out of the soil where it grows. These toxins and heavy metals are pulled into the plant and may be found in products made from the plant. This means that THC products may be at high risk of contamination with heavy metals and other harmful chemicals.

What should I tell my health care provider before using THC?

Tell your health care provider about all of your health conditions and any prescription or over-the-counter (OTC) medicines, vitamins/minerals, herbal products, and other supplements you are using. This will help them know if THC is right for you.

In particular, make sure that you discuss any of the following.

Current and Past Health Conditions.Tell your health care provider if you have any of the following.

• A genetic condition that affects how your body processes medicines, such as a CYP2C9 polymorphism
• Drink large amounts of alcohol
• Heart problems
• High or low blood pressure
• Liver problems
• Mental health problems, such as depression, a past suicide attempt, anxiety, hallucinations, paranoia, or psychosis
• Seizures
• Substance use disorder, including cocaine, methamphetamine, or opioid use disorder
• Upcoming surgery or medical procedure

Other Medicines and Supplements.THC may interact with other medicines and supplements. Before using THC, tell your health care provider about any prescription or over-the-counter (OTC) medicines, vitamins/minerals, herbal products, and other supplements you are using. See the Interactions section for more details.

Pregnancy. THC may cause harm to a fetus.  Tell your health care provider if you are pregnant or plan to become pregnant.

Breastfeeding. THC passes into breast milk and may continue to pass into breast milk for weeks after use. This may cause harm to your baby. Tell your health care provider if you are breastfeeding or plan to breastfeed.

Interactions

Does THC interact with foods or drinks?

There are no known interactions between THC and foods or drinks.

It is unknown if drinking alcohol will affect THC. But the risk of serious side effects may be increased if you drink alcohol while using THC. It is best to limit the amount of alcohol you drink.

Does THC interact with medicines (drug interactions)?

Always tell your health care provider about any prescription or over-the-counter (OTC) medicines, vitamins/minerals, herbal products, and other supplements you are using.

In particular, make sure that you discuss if you are using any of the following before using THC.

• Any medicine that causes dizziness and sleepiness, such as prescription pain medicines, sleep medicines, or medicines for anxiety
• Any medicine that can affect your blood pressure or heart rate
• A barbiturate, such as butalbital, phenobarbital, or primidone, which is a medicine that may be used to treat insomnia, migraines, or seizures
• A benzodiazepine, such as clonazepam (Klonopin), diazepam (Valium and others), or lorazepam (Ativan and others), which is a medicine used for anxiety, muscle spasms, or seizures
• A muscle relaxant, such as carisoprodol (Soma), cyclobenzaprine, metaxalone, or tizanidine (Zanaflex)
• An opioid, such as codeine, fentanyl, morphine, oxycodone, or tramadol, which is a medicine used to treat certain types of pain
• Street drugs, such as cocaine, heroin, or methamphetamine

Many other medicines may alter the blood levels of THC, and vice versa. Tell your health care provider about all medicines that you take or have recently taken.

The interactions between THC and medicines are not fully understood. As with most unapproved ingredients, the research on drug interactions with THC is incomplete. Always check with your health care provider before using THC with any medicines.

Dosing

What should I do if I accidentally use too much THC?

If you or someone else has used too much THC, get medical help right away, call 911, or contact a Poison Control center at 800-222-1222.

THC comes in many forms and can be used in many ways. Some people have had physical dependence while using THC, which means their bodies come to rely on it. Stopping THC suddenly can lead to withdrawal. Read the product label closely, and speak with a health care provider before using THC. Do not use double or extra doses.