Can You Overdose on Cannabis?
6 min readBeginner Level
The facts about cannabis overdose — why it's not fatal, what 'greening out' feels like, how to handle it, and when to seek medical help.
This guide is for educational purposes only. Cannabis is illegal in the UK without a medical prescription. Always consult a healthcare professional before making decisions about cannabis use.
No. There are zero documented cases of a fatal overdose from cannabis alone. The estimated lethal dose of THC is so high — approximately 40,000 times a typical dose — that it is physically impossible to consume enough through smoking, vaping, or eating edibles to cause death.
This does not mean cannabis is harmless. While you cannot die from cannabis toxicity, you can certainly have a highly unpleasant experience, and the effects can be dangerous in certain situations — particularly driving or operating machinery.
Cannabis does not suppress the central nervous system in the way that opioids, alcohol, or benzodiazepines do. There is no risk of respiratory depression (stopping breathing), which is the primary cause of fatal overdoses from those substances.
However, it is possible to have a serious adverse reaction that requires medical attention — such as severe panic attacks, vomiting (cannabinoid hyperemesis syndrome), or accidents caused by impairment.
Greening out (also called a 'whitey' or cannabis overdose in common slang) occurs when you consume more cannabis than your body can comfortably handle. Symptoms include: extreme dizziness or lightheadedness, nausea or vomiting, rapid heart rate, sweating and chills, anxiety or panic, paranoia, confusion, and feeling faint or shaky.
Greening out is most common with edibles (due to delayed onset leading to overconsumption), high-THC concentrates, and in people with low tolerance. It can also happen to experienced users who accidentally consume more than expected.
The experience is extremely unpleasant but not medically dangerous. Most episodes resolve on their own within 1-4 hours. The effects of edibles can last longer — up to 8-12 hours — but the peak discomfort usually passes within a few hours.
First-time cannabis users should be especially careful. Starting with a very low dose (2.5mg THC for edibles, one small puff for vaping) in a safe, comfortable environment dramatically reduces the risk of greening out.
Step 1: Stay calm. Remind yourself that no one has ever died from cannabis. You are not in danger. The effects will pass. Panic makes everything worse, so take slow, deep breaths.
Step 2: Find a comfortable, quiet space. Lie down if you feel dizzy or nauseous. Reduce stimulation — turn off bright lights, loud music, and screens. Put on something calming like ambient music or a familiar show.
Step 3: Drink water and eat something. Food helps absorb THC and can reduce discomfort. Black pepper contains beta-caryophyllene, which can counteract THC's effects — chewing a few peppercorns or smelling freshly ground pepper can help.
Step 4: CBD can counteract THC. If you have CBD oil or gummies on hand, taking 25-50mg CBD can reduce anxiety and paranoia. This is one reason having a CBD product available is a good idea whenever you try a new THC product.
Step 5: If symptoms are severe or last longer than expected, call NHS 111 for medical advice. Go to A&E only if you have chest pain, trouble breathing, severe vomiting, or are unable to stay conscious.
Cannabinoid Hyperemesis Syndrome (CHS) is a rare condition that affects a small percentage of long-term, heavy cannabis users. It causes cyclical episodes of severe nausea, vomiting, and abdominal pain.
CHS has three phases: prodromal (morning nausea without vomiting), hyperemetic (intense nausea and vomiting, often leading to dehydration), and recovery (symptoms subside after stopping cannabis use).
The only reliable treatment for CHS is complete cessation of cannabis use. Hot showers or baths often provide temporary relief during episodes — this is one of the diagnostic signs of the condition.
CHS is poorly understood and often misdiagnosed. If you experience regular unexplained nausea or vomiting, especially if you're a regular cannabis user, consult your GP and mention the possibility of CHS.
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About the Author
DM
Dave Mak
Dave founded The Budophile to create clear, honest cannabis education for UK beginners. With a background in health research and a network of specialist contributors, he ensures every guide is accurate, evidence-based, and practical. He also runs Baked & Rated for product reviews and The Green Prescription for medical cannabis access guidance.
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