Medically Reviewed by
Jason Crawford

Article Last Updated on January 3, 2023

The 2019 (COVID-19) pandemic that started last year has resulted in a significant increase in cannabis use, as well as other drug use, as people are trying to cope with the crisis any way they can.

And while regular cannabis users generally don’t experience many side effects as a result of being used to weed, first-time users may experience dizziness, shortness of breath, a green out, and even passing out.

Whether you vape it, smoke it in a joint, make edibles, or use a dab rig, fainting can happen to you while consuming marijuana. In this article, we’ll explain why that is so.

What’s a Cannabis Green Out?

Before we dive into why people pass out after consuming cannabis, we’ll first explain what greening out is. A “green out” is a physiological or psychological panic attack that can happen as a result of smoking weed, and it’s typically caused by smoking or ingesting too much cannabis in a short period of time. 

Symptoms of a green out include heart palpitation, anxiety, paranoia, sweating, nausea, and the sensation of a spinning room. In general, a green out is a brief experience, but it can sometimes cause vomiting and may even be accompanied by fainting.

Why Does Marijuana Make Some People Faint?

It doesn’t matter whether you’ve smoked a joint a thousand times as fainting can happen even to seasoned marijuana users. One moment you’re smoking a joint with your friends, and the next one you’re flat on the floor. If you’re a newbie, it can even happen after taking one hit of weed if the particular cannabis strain you’re smoking is pretty strong.

If you have underlying health conditions like low blood pressure or low blood sugar, it’s more likely that you may pass out during a smoking session. That’s because cannabis can lower both blood pressure and blood sugar.

One of the main cannabinoids found in cannabis, THC, can act as a vasodilatator in the body, which decreases blood pressure, and can lead to a blackout.

To avoid that, you may opt for a strain that is low in THC, but high in CBD, as it can limit the effects on the blood vessels, which, in turn, minimizes potential fainting.

Signs of Fainting From Recreational and Medical Marijuana

Even though marijuana use is very common nowadays, both recreationally and as an alternative medicine for treating conditions like ADHD, chronic pain, anxiety, as well as other conditions, there can be side effects to using it, like fainting.

Medical cannabis treatments generally focus on using CBD to treat and ameliorate most of these conditions, although strains with both THC and CBD are also used.  

If you’re a marijuana user, or even if you’re just trying marijuana for the first time, there are some telltale signs that you’ll most likely faint, and you need to recognize them before they happen.

You may start to feel dizzy, become nauseous, break out in a sweat, have a headache or blurred vision, and you may even have some trouble catching your breath. You may even look pale and unresponsive to the people around you. All of these signs indicate that you might be about to pass out.

If you’re experiencing some of these symptoms, it might be a good idea to find a place to sit down (and calm down) so you can enable your body to adjust to the THC and prevent fainting.

Causes for Blacking Out

There can be many causes for losing consciousness when smoking weed, but most of them aren’t serious and can be avoided.

The Consumption Method

One cause can be the cannabis consumption method. Smoking a joint, or using vaporizers and bongs, are methods that deliver a higher dose of THC in a short period of time. 

The Potency of the Weed

Fainting may also be related to the potency of weed. The more potent the bud, the higher the THC and the higher the chances of fainting, especially in inexperienced smokers whose cannabis tolerance is still low (and its potency may come as a shock to the body).

Drug Interactions

Passing out can even be a result of drug interactions with weed. If you have some medical conditions which require that you take some meds regularly, they might not react with weed that well. For example, a 2002 study revealed that people with cardiovascular diseases who consume high amounts of THC may be risking their lives by consuming weed as it can increase the catecholamine levels, carboxyhemoglobin, and postural hypotension. Those are all parameters related to conditions like diabetes, heart disease, and others.

Smoking Weed While Standing

It may sound weird, but smoking marijuana while standing may trigger postural hypotension which can lead to a loss of consciousness. What happens here is that when you stand, gravity pulls the bloodstream down below your diaphragm, which restricts the normal blood flow to the brain and the heart – so your blood pressure drops. Since marijuana also lowers your blood pressure momentarily, you may start feeling lightheaded, and even faint.

Using Impure Marijuana

Smoking impure marijuana can be another cause for greening-out or fainting. Laced weed is a common problem, especially if you buy from people you don’t know well (or unreputable sources). Weed can be laced either with chemicals, like laundry detergent or lead, or heavier drugs, such as cocaine or meth. Either way, smoking laced weed will definitely feel different from smoking normal weed and the combination of cannabis and other substances can often lead to some very unpleasant side effects (including fainting).


Finally, marijuana users can experience a blackout due to the vasodilating effects of THC. This cannabinoid has the ability to expand the blood vessels which, in turn, momentarily decreases the blood pressure in the body – and sometimes, this chain reaction can make you pass out.

How Common Is Fainting From Cannabis Use?

Let’s see… How common is a fainting spell when using cannabis? Well, the underlying biological mechanisms that are involved in passing out are very complex. While sometimes the cause is evident, like having a lower blood sugar as a result of a hit of weed, at other times they’re unknown.

As to the question of how common can fainting spells occur, the answer is unclear. There’s a chance that it can only happen once and never again, but fainting as a result of smoking weed can also be a common occurrence for some users.  

In order to prevent potential fainting episodes when you do smoke weed, make sure you don’t smoke on an empty stomach, hydrate properly, check if weed may have some potential side effects when it’s combined with some medication you’re using, and take it easy. Keep in mind that you don’t need to rush the experiment and take a lot of hits at once.

Cannabis and Dizziness: Should You Be Worried?

Many marijuana users experience slight dizziness when they smoke weed, so it’s quite common – and usually, it shouldn’t be a cause of concern. It’s important to remember that cannabis affects everyone differently, and how you react to it at any given moment can be influenced by the strain you’re smoking, your consumption method, your mood, and even the people you’re with. 

By listening to your body and trying to avoid the triggers that might cause you to pass out, you can reduce the chances of experiencing this side effect. However, if you ever feel like it’s something out of the ordinary, of course, you should consult with a professional.

How to Prevent Fainting From Marijuana

If you’re prone to experiencing lightheadedness and fainting when smoking weed, there are some things you can do to prevent it (or at least make it more manageable).

Try a Different Strain

One of the first things you can do is to switch up the strain. You might be using a weed strain with a high THC content (which may be the culprit), especially if you have a low weed tolerance, to begin with. Switching to a weed strain with lower THC and higher CBD content may help you, especially if it contains some calming terpenes as well (such as myrcene or caryophyllene). 

Eat Something Before You Smoke

Smoking may give you the munchies and you want to save your appetite for later, but it’s much better to smoke after you’ve already eaten – plus it’ll reduce the risk of passing out. Smoking on an empty stomach may heighten the effects of THC and make your body more vulnerable to its impact. You don’t have to stuff yourself, just eat a regular meal as you normally would.

Change Your Consumption Method

As we previously said, some consumption methods deliver more THC than others. For example, dabbing concentrates is very powerful and bongs produce large quantities of smoke. Edibles can also make you dizzy, especially because they start circulating around the body later and their effects are more pronounced. Therefore, you can switch it up. Smoking a joint or a one-hitter may be a safer choice, or even a bowl or a bubbler, as they don’t tend to produce a lot of smoke.

Go Slow and Steady

Smoking weed is all about enjoying it and not rushing. Sometimes you may be close to passing out because of the sudden influx of THC which shocks the body, especially if you’re smoking a potent bud. Therefore, pace yourself and enjoy yourself. Just take smaller puffs and wait between hits so that your body can adjust – and definitely don’t try to finish the whole joint yourself!

Start Your Session Sitting Down

We already mentioned that standing up may increase your chances of feeling lightheaded or fainting, so sitting down while smoking may make you feel more secure and comfortable, especially if you’re still a newbie. You want to feel secure – so that if you feel a fainting spell coming up, you can lie down. Or even if you don’t feel dizzy, you’ll just be a lot more comfortable.

Other Cannabis Side Effects

The side effects of marijuana usually aren’t serious, but they can be unpleasant and ruin your mood. These most commonly happen because you may have taken too much, or the strain you took is very potent, or your THC tolerance is low (for whatever reason). Apart from fainting, there are other adverse effects that are more common, and these are:

  • Cottonmouth (dry mouth)
  • Red/dry eyes
  • Anxiety
  • Paranoia
  • Nausea
  • Increased heart rate
  • Psychosis (in rare cases and usually in high doses)

These side effects can be averted if you stick to your ideal dose, meaning the dose that gets you high without causing side effects. Also, your weed tolerance will increase over time, but it’s important to always start with a low dose and slowly increase it.

Final Thoughts on Smoking Cannabis and Fainting

If you’ve been experiencing fainting spells and blood pressure changes, no matter if they’re weed-related or not, it’s always a good idea to consult your general practitioner or a healthcare provider to discuss why that may be the case. After all, for people with cardiovascular conditions, fainting may be a result of something more serious happening in the body.

It’s also important to know and recognize the telltale signs that indicate a potential blackout to be able to prevent it. And if you feel it coming, make sure you take a seat until the symptoms pass, and stop smoking marijuana for the time being.

A passionate advocate for the benefits of cannabis. Fraser Horton, who has a background in botany and a strong love of nature, has spent years researching how cannabis affects the body and mind. He established Leaf Nation in 2020, where he has devoted himself to educating people about the legalisation of marijuana and its safe and responsible use. Fraser is committed to highlighting cannabis’ potential for improving wellness and working to dispel the stigma associated with its use.


The information presented on this page is provided as a public service to aid in education and is derived from sources believed to be reliable. Readers are responsible for making their own assessment of the topics discussed here. In no event shall Leaf Nation be held reliable for any injury, loss or damage that could happen if using or abusing drugs.