Can Weed Make You Pass Out? (Why It Might Happen and How to Prevent It)

Cannabis has been used for centuries for a variety of reasons. Some people use it to help relax and unwind, while others report that it makes them sleepy. These results are not guaranteed, however. For some, especially with high doses, cannabis can have undesirable effects.

Can Weed Make You Pass Out?

Taking too much cannabis in any form can lead to over-intoxication, or greening out. The most common undesirable effects of consuming too much cannabis are relatively minor and can include lightheadedness, dizziness, or anxiety. In more extreme cases, cannabis has been linked to episodes of dizziness and, rarely, fainting during upright posture.

Fainting from cannabis is not a pleasant experience and can be dangerous, depending on the situation. To protect yourself, it’s a good idea to learn what causes people to pass out from weed and how to avoid it happening to you.

What May Cause Fainting From Weed?

People who faint after smoking weed have likely ingested too large a dose of cannabinoids such as THC, the compound most responsible for the intoxicating effects of cannabis. 

Note that “too large a dose” is a subjective phrase. Everyone’s endocannabinoid system responds to weed a little bit differently. What works for one person may be far too much for the next, so it’s important to proceed with caution. The adage “start slow, go slow” is good advice, even for experienced cannabis users.

The effects of taking too large a dose can vary. Some people may feel uneasy or anxious, while others might feel sedated. When people pass out from weed, one of four reasons may likely the cause.

Vasodilation

Current research suggests that a sudden change in heart rate and blood pressure is a likely reason people faint after using cannabis. 

THC can cause peripheral vasodilation with reflex tachycardia. These hemodynamic shifts can lower blood pressure and, in some people, trigger dizziness or, rarely, syncope.^1,2

A slight drop in blood pressure is usually not a significant concern, as vasodilation is a natural physiological process that occurs from time to time. However, a sudden drop in blood pressure could cause various symptoms, such as blurred vision, dizziness, or vasovagal syncope (fainting).

Vasovagal syncope is a sudden drop in both heart rate and blood pressure. It sometimes manifests as fainting, such as when a person sees blood or suffers an emotional shock. 

While a drop in blood pressure has been observed with cannabis use, the effect is not universal. Conversely, immediately after smoking, THC has also been linked to increased heart rate and blood pressure. Increased heart rate has also been linked to fainting.

Method of Consumption

The cause of passing out from weed can also often be linked to the method of cannabis consumption. Cannabis concentrates are often responsible for delivering high, concentrated doses of cannabinoids. Some concentrates test between 60% and 90% THC, much stronger than typical flower (15% to 30%). Patients who are not accustomed to such doses and those who have relatively low tolerance are most susceptible and may become uncomfortably high or even pass out.

Very deep inhalations and breath-holding may contribute to lightheadedness in some people, independent of cannabis’ effects.

Because they can take up to an hour or more to take effect, taking edibles can also result in too large a dose of THC. Users sometimes become impatient waiting for the first dose to take effect, so they have more. This can lead to inadvertently taking too high a dose and may cause unpleasant effects, including passing out. 

Standing While Smoking Weed

A consumer’s posture while smoking cannabis has also been associated with passing out from weed. Standing too quickly after taking a hit can lead to a head rush (orthostatic hypotension), which can make you feel lightheaded, dizzy, or even cause you to faint.

Smoking weed while standing upright can also cause some people to pass out from cannabis. Some clinical studies have linked cannabis and orthostatic hypotension — a drop in blood pressure upon standing — with dizziness and fainting documented in some cases.³

In most cases, head rushes are mild and not a cause for concern. However, if they occur frequently or severely, consult a qualified medical professional.

Using Contaminated Weed

Illicitly adulterated cannabis — such as products dipped in embalming fluid or PCP (‘wet weed’) — can cause severe, unpredictable effects, including loss of consciousness. Synthetic cannabinoids (‘Spice’) have also been tied to seizures and emergency room visits. These risks are associated with unregulated, illicit products, not licensed dispensary cannabis.⁴ 

Unregulated synthetic cannabinoids, collectively and colloquially known as “spice,” can also lead to unwanted and potentially dangerous effects. A 2011 study found that synthetic cannabinoid products have been associated with a number of toxic side effects resulting in trips to the emergency room, including seizures in extreme cases.⁵

Signs You Might Be Getting Too High

People who have fainted from cannabis often report noticing signs of being too high beforehand. Take a break from using cannabis if you notice any of the following symptoms:

• Paleness or whiteness of the skin
• Tunnel vision
• Ringing in the ears (tinnitus)
• Nausea or vomiting
• Lightheadedness or dizziness
• Excessive sweating

How Can You Avoid Passing Out From Weed?

Nobody wants to deal with the unwelcome effects of getting too high, including passing out. Luckily, taking a few precautions can help you avoid fainting from weed. 

• Don’t smoke weed while standing. Smoking while standing or standing up immediately after taking a hit can impact blood flow Instead, find a comfortable place to sit and relax while you smoke, and continue to do so for several minutes afterward.
• Avoid contaminated weed. Cannabis from regulated sources has usually to be lab-tested for safety, so buying from a licensed dispensary (when possible) can help significantly reduce the risk of contamination.
• Consider your method of consumption. If you have low tolerance to cannabis or are prone to passing out, small puffs from a joint might be a better option than bong hits, dabs, or vapes.
• Always wait to feel the effects. When using cannabis edibles, always wait at least an hour or more to gauge the effects before taking another dose.
• Try microdosing. By taking a very low dose of THC, you are less likely to experience unwelcome effects from cannabis, including fainting.
• Consider CBD-dominant strains. Choosing low-THC, high-CBD  strains may make it easier to avoid greening out.

Try CBD-Dominant Strains to Avoid Getting Too High

Most cannabis strains available in dispensaries are THC-rich cultivars, some with THC levels approaching 30%. Not all cannabis enthusiasts, however, want products that are so potent, creating a market for relatively low-THC options. 

Instead of relying on strain names — which don’t guarantee potency — ask your budtender for CBD-dominant flower (for example, ~10% to 20% CBD with ≤1% to 5% THC) or balanced 1:1 options. Always check the label or certificate of analysis (COA) for actual THC and CBD percentages.

Take a Pass on Passing Out from Weed

Many people find cannabis enjoyable. If you find yourself fainting from consuming weed, consider the causes of the phenomenon and how it can be avoided to ensure you have the best experience possible.

References

1. Richter, J. Sebastian, et al. “A Systematic Review of the Complex Effects of Cannabinoids on Cerebral and Peripheral Circulation in Animal Models.” Frontiers in Physiology, vol. 9, 29 May 2018, 10.3389/fphys.2018.00622. Accessed 6 Jan. 2022. ↩︎
2. Ramanlal, Riddhi, and Vikas Gupta. “Physiology, Vasodilation.” PubMed, StatPearls Publishing, 2020, www.ncbi.nlm.nih.gov/books/NBK557562/#:~:text=Vasodilation%20is%20the%20widening%20of. ↩︎
3. Mathew, R. J., et al. “Middle Cerebral Artery Velocity during Upright Posture after Marijuana Smoking.” Acta Psychiatrica Scandinavica, vol. 86, no. 2, Aug. 1992, pp. 173–178, 10.1111/j.1600-0447.1992.tb03247.x. Accessed 2 Dec. 2021. ↩︎
4. Gilbert CR, Baram M, Cavarocchi NC. “Smoking wet”: respiratory failure related to smoking tainted marijuana cigarettes. Texas Heart Institute journal. 2013;40(1):64-67. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3568288/ ↩︎
5. Havenon A de, Chin B, Thomas KC, Afra P. The Secret “Spice”: An Undetectable Toxic Cause of Seizure. The Neurohospitalist. 2011;1(4):182-186. doi:https://doi.org/10.1177/1941874411417977 ↩︎

The information in this article and any included images or charts are for educational purposes only. This information is neither a substitute for, nor does it replace, professional legal advice or medical advice, diagnosis, or treatment. If you have any concerns or questions about laws, regulations, or your health, you should always consult with an attorney, physician or other licensed professional.