What Is Greening Out? Symptoms, Duration and What to Do

What is greening out? It is the informal name for feeling acutely unwell after taking more THC than your body can handle: a racing heart, dizziness, nausea, sweating and, very often, anxiety or panic. The most important acute adverse effects of too much cannabis are anxiety and panic attacks, together with a faster heart rate and changes in blood pressure [1]. It feels frightening, but for most healthy adults it passes as the THC wears off: within a few hours after smoking or vaping, and up to around 12 hours after an edible [1]. Chest pain, fainting, trouble breathing or a child or pet who has eaten cannabis are emergencies.

Most greening out from edibles starts with a second dose taken too early: see how long to wait before taking more edibles.

What is greening out, and is it an overdose?

"Greening out" (also "whitey" in the UK, "wit wegtrekken" in Dutch) is a user term, not a medical diagnosis. Doctors usually describe the same event as acute cannabis intoxication. It is the same thing many people call a THC overdose, but it is not the life-threatening kind of overdose seen with opioids or alcohol, which stops breathing: the main effects are on mood, the heart and blood pressure [1]. The longer answer to whether a fatal THC overdose is possible is on the page can you overdose on THC?.

Being unpleasant is not the same as being harmless. In a review of emergency visits at a large hospital in Colorado, 2,567 visits between 2012 and 2016 were at least partly caused by cannabis; the common reasons included intoxication, acute psychiatric symptoms and cardiovascular symptoms [2].

Symptoms of greening out

The symptoms come from two directions at once, the mind and the circulation. Anxiety reactions and panic attacks are the acute symptoms most often linked with cannabis use [3], and the heart speeds up while blood pressure shifts [1]. People commonly describe:

• Mind: sudden anxiety, panic, paranoia, a feeling that something is badly wrong, confusion, a distorted sense of time.
• Body: a fast or pounding heartbeat, dizziness or light-headedness (worse when standing up quickly), pale and sweaty skin, feeling hot or cold, nausea and sometimes vomiting.
• Movement and senses: heavy limbs, poor coordination, feeling very sleepy or "stuck".

Repeated, severe vomiting in someone who uses cannabis every day is a different condition, cannabinoid hyperemesis syndrome. In the Colorado study it caused 18.0% of the emergency visits linked to inhaled cannabis [2].

How long does greening out last?

It lasts as long as the THC peak behind it, so the way the cannabis was taken matters most. The timings below come from a pharmacology review of THC [1]:

Route	Effects start	Strongest point	Fades
Smoked or vaped	Seconds to a few minutes [1]	After 15 to 30 minutes [1]	Within 2 to 3 hours [1]
Edible or drink	After 30 to 90 minutes [1]	After 2 to 3 hours [1]	Lasts about 4 to 12 hours [1]

The edible delay is the classic trap. The US Centers for Disease Control and Prevention (CDC) notes that edibles take 30 minutes to 2 hours to feel, which is why some people take more before the first dose has started working [4]. Edibles also stand out in hospital data: between 2014 and 2016 they caused 10.7% of the cannabis-attributable emergency visits in the Colorado study, while making up only 0.32% of the THC sold in the state [2]. Why edibles are so unpredictable is explained in why edibles do not work the same for everyone.

What to do if you are greening out

There is no antidote that switches a THC high off. What helps is making the hours until it fades safe and calmer:

• Stop taking more. No more cannabis, and no alcohol or other drugs on top.
• Sit or lie down somewhere safe and quiet. Get up slowly, since dizziness on standing is common. If you feel sick, lie on your side.
• Remind yourself what is happening. The panic is a known effect of THC and it fades as the THC level falls [1][3]. Slow breathing, a familiar person, low light and calm music help many people ride it out.
• Sip water and eat something light if you can. This does not lower THC, but it helps with a dry mouth and an empty stomach.
• Do not drive and do not be left alone if you feel very unwell.
• Helping someone else? Stay with them, keep them calm and sitting or lying on their side, and watch their breathing and how responsive they are.

When greening out is an emergency

Get urgent medical help (the local emergency number, or a poison centre for advice) if any of these happen:

• Chest pain or pressure, a very fast or irregular heartbeat, or fainting.
• Trouble breathing, a seizure, or the person cannot be woken properly.
• Severe confusion, hallucinations, or thoughts of harming themselves or others.
• Vomiting that will not stop, or cannabis taken together with alcohol, medicines or other drugs.
• A child has eaten an edible. The CDC warns that children who consume THC products can become very sick, with problems walking or sitting up or a hard time breathing, and advises contacting a poison centre or, in an emergency, the emergency services [4]. US poison centres recorded 207 edible exposures in children under 6 in 2017 and 3,054 in 2021, an increase of 1,375%; 22.7% of those children were admitted to hospital [5]. In Colorado, the median age of children evaluated for cannabis exposure was about 2 years [6].
• A dog or cat has eaten cannabis. Call a vet or an animal poison line at once. In a series of 125 dogs treated in Colorado, two dogs died after eating baked goods made with cannabis butter [7].

If in doubt, call. Medical staff need to know what was taken and when, not to judge it.

Folk remedies: what the evidence says

Several tips circulate online for "coming down" faster. None is proven to reverse a high, and some evidence is only a first lab result:

• CBD: a systematic review of 16 studies with 466 participants found mixed results; CBD reduced some THC effects in some studies but not consistently across studies and outcomes [8]. It is not a reliable rescue.
• Lemon and limonene: in a controlled study of 20 adults, vaporised d-limonene inhaled together with 30 mg of THC reduced ratings of feeling anxious and paranoid [9]. That was a pure terpene in a laboratory, not lemon juice or lemon peel, and it has not been tested as a treatment.
• Black pepper: its terpene beta-caryophyllene binds the CB2 receptor [10], which is why sniffing or chewing peppercorns is suggested. No human study shows that pepper reverses a THC high.
• Cold showers, coffee, exercise: no evidence that they lower THC. A shower can calm some people but is risky if you are dizzy.

More on the plant compounds behind these tips is in what a terpene is.

How to avoid greening out

• Know the strength of what you take. For homemade edibles the edible dosage calculator estimates how much THC a portion holds.
• With edibles, wait for the full effect before taking any more: onset can take up to 2 hours [4].
• Do not combine cannabis with alcohol or other drugs.
• Be careful with a new product, a new route or a long break, and use cannabis in a safe place with someone you trust.
• Store edibles locked away and out of sight of children and pets [4].

A first experience tends to feel stronger; see how long a first high lasts. If anxiety keeps coming back with cannabis, read cannabis and anxiety.

Frequently asked questions

Can you die from greening out?

Greening out itself is rarely life-threatening for a healthy adult, because THC does not stop breathing the way opioids or alcohol can; its main acute effects are anxiety, panic, a faster heart rate and blood pressure changes [1]. It can still be dangerous: it sends people to emergency departments with psychiatric and cardiovascular symptoms [2], and children who eat edibles can become very sick [4].

How long does greening out last?

After smoking or vaping, effects peak at 15 to 30 minutes and fade within 2 to 3 hours. After an edible they peak at 2 to 3 hours and can last about 4 to 12 hours [1].

How do you stop greening out fast?

Nothing switches a THC high off. Stop taking more, sit or lie down somewhere safe, breathe slowly, sip water and wait for the THC level to fall [1]. CBD gave mixed results in studies [8].

What does greening out feel like?

Usually a wave of anxiety or panic with a pounding heart, dizziness, sweating and nausea. Anxiety and panic attacks are the acute symptoms most often linked with cannabis [3].

When should you go to the hospital for greening out?

With chest pain, fainting, trouble breathing, a seizure, severe confusion, vomiting that will not stop, a mix with alcohol or other drugs, or when a child or a pet has eaten cannabis [4].

Sources

1. Grotenhermen F. Pharmacokinetics and pharmacodynamics of cannabinoids. Clinical Pharmacokinetics. 2003;42(4):327-360. doi:10.2165/00003088-200342040-00003
2. Monte AA, Shelton SK, Mills E, Saben J, Hopkinson A, Sonn B, Devivo M, Chang T, Fox J, Brevik C, Williamson K, Abbott D. Acute illness associated with cannabis use, by route of exposure: an observational study. Annals of Internal Medicine. 2019;170(8):531-537. doi:10.7326/M18-2809
3. Crippa JA, Zuardi AW, Martin-Santos R, Bhattacharyya S, Atakan Z, McGuire P, Fusar-Poli P. Cannabis and anxiety: a critical review of the evidence. Human Psychopharmacology. 2009;24(7):515-523. doi:10.1002/hup.1048
4. US Centers for Disease Control and Prevention. Cannabis and poisoning. Last reviewed 15 February 2024. cdc.gov
5. Tweet MS, Nemanich A, Wahl M. Pediatric edible cannabis exposures and acute toxicity: 2017-2021. Pediatrics. 2023;151(2):e2022057761. doi:10.1542/peds.2022-057761
6. Wang GS, Le Lait MC, Deakyne SJ, Bronstein AC, Bajaj L, Roosevelt G. Unintentional pediatric exposures to marijuana in Colorado, 2009-2015. JAMA Pediatrics. 2016;170(9):e160971. doi:10.1001/jamapediatrics.2016.0971
7. Meola SD, Tearney CC, Haas SA, Hackett TB, Mazzaferro EM. Evaluation of trends in marijuana toxicosis in dogs living in a state with legalized medical marijuana: 125 dogs (2005-2010). Journal of Veterinary Emergency and Critical Care. 2012;22(6):690-696. doi:10.1111/j.1476-4431.2012.00818.x
8. Freeman AM, Petrilli K, Lees R, Hindocha C, Mokrysz C, Curran HV, Saunders R, Freeman TP. How does cannabidiol (CBD) influence the acute effects of delta-9-tetrahydrocannabinol (THC) in humans? A systematic review. Neuroscience and Biobehavioral Reviews. 2019;107:696-712. doi:10.1016/j.neubiorev.2019.09.036
9. Spindle TR, Zamarripa CA, Russo E, Pollak L, Bigelow G, Ward AM, Tompson B, Sempio C, Shokati T, Klawitter J, Christians U, Vandrey R. Vaporized D-limonene selectively mitigates the acute anxiogenic effects of delta-9-tetrahydrocannabinol in healthy adults who intermittently use cannabis. Drug and Alcohol Dependence. 2024;257:111267. doi:10.1016/j.drugalcdep.2024.111267
10. Gertsch J, Leonti M, Raduner S, Racz I, Chen JZ, Xie XQ, Altmann KH, Karsak M, Zimmer A. Beta-caryophyllene is a dietary cannabinoid. Proceedings of the National Academy of Sciences of the USA. 2008;105(26):9099-9104. doi:10.1073/pnas.0803601105

Related: can you overdose on THC?, how long a first high lasts, cannabis and anxiety and what a terpene is.

Educational safety information. Not medical advice and not a dosing guide. If you are worried about someone, contact a doctor, a poison centre or the emergency services.