Greening Out: Symptoms, How Long It Lasts and What to Do

Greening out happens when someone consumes more THC than their body can comfortably handle. The person may suddenly become pale, sweaty, dizzy, nauseated or intensely anxious. Their heart may race. The room may feel as if it is spinning. Some people vomit, become confused or believe something terrible is about to happen.

It can be frightening, but most episodes improve as the effects of the cannabis wear off. The immediate priority is to keep the person calm, prevent falls or choking and watch for symptoms that require medical attention.

Move the person to a quiet place. Have them sit or lie down. If they are vomiting or becoming very sleepy, place them on their side and stay with them. Do not let them drive, take a shower alone or use alcohol or another substance to try to counteract the THC.

Call 911 if the person collapses, has trouble breathing, experiences a seizure, develops chest pain or cannot be awakened. Contact Poison Control at 1-800-222-1222 if you are uncertain what was consumed or how serious the reaction may be.

Any suspected cannabis ingestion by a young child should be taken seriously. THC products can cause severe sleepiness, problems walking and breathing difficulties in children. Edibles are a particular concern because they may resemble ordinary candy, brownies or snack foods.

What Does Greening Out Mean?

"Greening out" is an informal term for an unpleasant reaction to cannabis. It usually follows a large amount of THC, although a dose that feels manageable to one person may overwhelm someone else.

A person who has greened out is no longer experiencing an ordinary or comfortable high. The physical effects may include nausea, sweating, dizziness and weakness. The mental effects may include panic, paranoia, confusion or a distorted sense of time.

The expression is sometimes compared with "blacking out" from alcohol, but the two are not the same. An alcohol blackout refers to a period in which the person may remain conscious but later cannot remember what happened. Greening out describes becoming physically or psychologically overwhelmed by cannabis.

Common Greening Out Symptoms

The symptoms can vary according to the product, THC concentration, amount consumed and the person's tolerance.

Common symptoms include:

• Nausea or vomiting
• Dizziness or difficulty standing
• Pale, cold or sweaty skin
• Shaking or weakness
• A rapid or pounding heartbeat
• Anxiety or panic
• Paranoia
• Confusion
• Sleepiness
• Poor coordination
• Feeling detached from the body or surroundings

At higher exposures, some people may experience hallucinations, severe agitation or psychotic symptoms. Cannabis can also impair judgment and coordination, increasing the risk of falls, vehicle crashes and other injuries. Anxiety and paranoia are common enough during a green-out that they have their own patterns — see can weed cause anxiety and panic attacks.

Do not assume that every unusual reaction is simply greening out. Cannabis products may contain unexpected ingredients, and a person may have consumed alcohol, medication or another drug at the same time.

Why Does Greening Out Happen?

Greening out is usually related to the amount of THC consumed, but several factors can raise the risk.

Edibles can take longer to affect someone

A person may eat a cannabis product, feel little at first and take a second dose. The first and second doses may then take effect close together.

This is sometimes called dose stacking. It is one of the most common ways people accidentally consume more THC than intended. Our guide to greening out from edibles covers this in detail.

Edibles can also produce effects that last longer than inhaled cannabis. The amount of THC in a serving may be unclear, especially in homemade or poorly labeled products.

High-potency products deliver more THC

Vape cartridges, concentrates and dabs may contain much higher THC concentrations than traditional cannabis flower. Someone accustomed to one product can still have an intense reaction after switching to a stronger form.

Alcohol can make the reaction worse

Using cannabis with alcohol can increase dizziness, nausea, poor coordination and impaired judgment. It also becomes more difficult to determine which substance is causing the symptoms.

Tolerance differs from person to person

A first-time or occasional user may react strongly to an amount that a frequent user considers small. A person returning to cannabis after a break may also have less tolerance than expected.

Body size alone does not predict how someone will react. Anxiety, medications, health conditions, food intake and the product itself can all matter.

How Long Does Greening Out Last?

There is no single timeline.

The effects of smoked or vaped cannabis generally begin sooner and may start improving within a few hours. Edibles can take longer to begin working and may produce effects lasting several hours. Fatigue, nausea or mental fog may continue after the strongest effects have passed.

The person should not drive or make important decisions simply because they feel somewhat better. Coordination, attention and judgment may remain impaired.

Seek medical guidance if severe symptoms are not improving, vomiting continues, the person cannot stay awake or there is uncertainty about what they consumed.

What to Do When Someone Is Greening Out

There is no dependable home remedy that instantly reverses THC intoxication. The goal is to reduce risk while the effects wear off.

Move to a calm setting

Noise, crowds and bright lights can intensify panic. Bring the person somewhere quiet where they can sit or lie down safely.

Stay with the person

Speak slowly and calmly. Remind them where they are and that help is available. Do not argue with paranoid thoughts or laugh at their reaction.

Encourage slow breathing

Panic can make a racing heart and shortness of breath feel worse. Slow breathing may help the person regain a sense of control.

Offer small sips of water

If the person is awake and able to swallow, small sips may help with dry mouth. Do not force food or large amounts of liquid, particularly if the person is vomiting or very drowsy.

Position them safely

If the person is vomiting or falling asleep, place them on their side to reduce the risk of choking. Do not leave them alone in a bathtub, shower or locked room.

Do not add another substance

Alcohol, sedatives and other drugs can make the situation more dangerous. Coffee will not sober someone up and may worsen anxiety or a pounding heartbeat.

When Greening Out Requires Emergency Care

Call 911 immediately if the person:

• Stops breathing or struggles to breathe
• Collapses or cannot be awakened
• Has a seizure
• Develops chest pain
• Shows extreme confusion or dangerous behavior
• Has severe hallucinations or agitation
• May have taken an unknown or contaminated substance
• Is at risk of harming themselves or someone else

If the situation does not appear immediately life-threatening but you need guidance, call Poison Control at 1-800-222-1222. The service is free and confidential. For more on what large THC doses do to the body, see can you overdose on weed.

Greening Out or Cannabinoid Hyperemesis Syndrome?

Greening out and cannabinoid hyperemesis syndrome, commonly called CHS, are not the same condition.

Greening out is an acute reaction associated with consuming too much THC at one time. CHS is linked to frequent, long-term cannabis use and causes repeated episodes of severe nausea, abdominal pain and vomiting. Some people with CHS report taking frequent hot showers because the heat temporarily reduces their symptoms.

Repeated vomiting can lead to dehydration and other complications. Someone experiencing recurring episodes should receive a medical evaluation. Stopping cannabis use is central to preventing CHS from returning.

When One Bad Experience Becomes a Pattern

A single episode may result from an edible that was stronger than expected. Repeated episodes deserve more attention.

It may be time to speak with a healthcare or behavioral health professional when someone:

• Regularly uses more cannabis than intended
• Continues using after repeated panic or vomiting
• Needs increasingly potent products to feel the same effect
• Cannot reduce or stop despite wanting to
• Uses cannabis as the primary way to manage anxiety, depression, trauma or sleep
• Experiences paranoia, hallucinations or other breaks from reality

The point is not to label every difficult cannabis experience as addiction. It is to recognize when cannabis is causing physical illness, interfering with daily life or worsening an underlying mental health condition.

A green-out passes. The pattern surrounding it may still be worth examining.

At a Glance

Greening out is an unpleasant reaction to consuming more THC than the body can comfortably handle. Symptoms commonly include nausea, dizziness, sweating, weakness, a racing heart, anxiety and confusion.

Move the person somewhere quiet, stay with them and keep them away from vehicles, stairs and water. Place them on their side if they are vomiting or very sleepy. Do not use alcohol or another drug to counteract the cannabis.

Call 911 for breathing problems, collapse, seizures, chest pain, unresponsiveness or dangerous behavior. Call Poison Control at 1-800-222-1222 if you need immediate guidance about a cannabis exposure.

Sources

• CDC: Cannabis and Poisoning
• CDC: Cannabis Frequently Asked Questions
• National Institute on Drug Abuse: Cannabis
• Poison Control: Cannabis Risks and Effects
• SAMHSA: Marijuana and CBD Risks

Prefer another language? Read about cannabinoid hyperemesis syndrome in Spanish: síndrome de hiperemesis cannabinoide, or in Hindi: कैनाबिनॉयड हाइपरमेसिस सिंड्रोम.