How Long Do Your Eyes Stay Red After Smoking Weed?

Sophia Delphi May 14, 2022 - 7 min read
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You’ve finished smoking a particularly potent and tasty bowl, and you make a quick bathroom stop. As you wash your hands (we know, we’re making quite an assumption here), you glance in the mirror and notice it.

“Damn, my eyes are really red this time!”

For most people, red eyes after smoking up are just part of the deal, along with the munchies and the pungent weed smell that clings to your clothes.

The good news is that bloodshot eyes caused by cannabis use don’t last long, don’t cause any permanent damage, and don’t carry any health risks.

The bad news – if you’re going to have to explain yourself to bosses, parents, or straight-edge friends – is that those red eyes usually take their own sweet time to disappear.

Exactly how long do your eyes stay red after smoking weed? And what causes them to turn red in the first place?

Thankfully, Mr. Answer Man is here to explain.

Why Do You Get Red Eyes After Using Weed?

Close-up image of a man's red eyes after smoking weed

Let’s start with two clarifications.

First, it’s not just weed smokers who are prone to get red eyes. Those who vape, consume edibles, or drop tincture into their tea or under their tongue, are in the same boat.

Second, you might be one of the lucky ones who don’t experience bloodshot eyes after spending a terrific night with Mary Jane. So the real question we have to answer is “why do so many people get red eyes?”

That answer requires a basic understanding of what happens when THC enters your body.

How THC Interacts With the Body

Of course, weed makes you high. But what’s more important to our discussion is how that happens.

The THC in weed has an unusual physical property: its molecules are almost identical to some of the neurotransmitters (chemical messengers) that deliver instructions throughout the body. That similarity allows the psychoactive cannabinoid to bind to the same “endocannabinoid receptors” normally used by neurotransmitters – giving THC molecules the power to affect how the brain responds while you’re using pot.

That’s the simple explanation of how weed is able to interact with the body in order to provide its mind-altering effects. The same mechanism explains many of the other effects of cannabis.

There are endocannabinoid receptors throughout the body, not just in the brain. And when you smoke or ingest marijuana, its THC binds to all of those to cause a number of other effects, like the couch-lock that some strains produce. For the purposes of this discussion, however, we’re concerned with one effect in particular.

THC and Blood Pressure

Most regular weed users experience a drop in blood pressure, almost immediately after THC hits their system and binds with endocannabinoid receptors. Scientists and medical experts aren’t certain why that happens, but research has documented the effect.

When blood pressure drops, that lowers the pressure that blood exerts against the walls of blood vessels and capillaries – allowing them to expand. The widening of blood vessels is known as vasodilation, and it allows more blood to circulate through the body.

Stay with us; we’re almost there. You’ll remember that endocannabinoid receptors are located all over the body; many of them are in the eyes and head. So when THC binds to them, pressure drops and vasodilation occurs. The vessels and capillaries in the eyes get wider, and more blood flows through them.

Guess what’s right behind the whites of the eyes? Capillaries. After you toke up, the effects of THC ensure that they’re loaded with blood – making the whites of the eyes look red.

Voila. We’ve now linked weed use to the telltale bloodshot eyes most of us are familiar with. THC lowers blood pressure, lower blood pressure fills the eyes’ capillaries with blood, and eyes appear to turn red.

But our initial question still remains.

How Long Will Your Eyes Stay Red After Smoking Weed?

It depends.

Since the THC in weed – and not the weed itself – is responsible for bloodshot eyes, let’s start there. The more THC you consume, the longer the phenomenon will last.

If you only take a few hits, that will have much less of an effect on your brain and blood pressure than if you spend the night smoking up. And when you smoke cannabis with high THC content, you’re not only getting blasted, but your red eyes will probably last longer. By contrast, smoking low-THC, high-CBD strains will reduce the amount of time that your eyes look bloodshot – if they even look bloodshot at all.

In fact, some smokers don’t have to deal with red eyes. They may have a high THC tolerance, or their bodies may just not respond to THC with lower blood pressure. Then there are those with hypertension; THC usually won’t lower their blood pressure enough to cause bloodshot eyes. On the other hand, a small number of people are allergic to marijuana or one of its components, and their eyes might turn red immediately.

All of that means there’s no firm number of hours (or days) that your eyes will stay red after smoking weed.

For some, primarily light smokers, it may only take an hour for the effect to wear off. Usually, the bloodshot eyes are gone in 3-4 hours. But if you smoke a lot of very potent ganja and have a low tolerance to THC, the red eyes can last as long as 12 hours. And as we’ve said, there are some weed smokers who never have to worry about using Visine or sunglasses to cover their eyes for a while.

There’s one more variable to consider. All forms of weed are likely to cause bloodshot eyes. But if cannabis has to be digested, THC won’t be released into the bloodstream until an hour or two after the pot has been swallowed. If you prefer edibles, it will take at least that long for red eyes to appear. And they could remain for 10-12 hours, because once the THC in edibles finally hits, it usually hits harder.

Can You Avoid Red Eyes, or At Least Shorten That Time Frame?

There’s really only one way to avoid bloodshot eyes after smoking weed: choose strains that are very low in THC. That’s not the advice most people want to hear, since low-THC flower won’t be very psychoactive. 

Otherwise, you might be able to reduce the amount of time you look stoned by enlisting the help of a vasoconstrictor, which will narrow blood vessels and lower the amount of blood behind your eyes.  Caffeine is a noted vasoconstrictor, so drinking coffee or eating chocolate could speed the disappearance of red eyes. Coldwater and ice are also vasoconstrictors, so it could help to put a cold compress or ice pack over your eyes (or to take a cold shower).

The one solution that obviously won’t help: smoking another bowl to help you forget about your red eyes.

How Long Do Your Eyes Stay Red After Smoking Weed: FAQ

Q: Can’t you avoid red eyes by drinking lots of water?
A: Some people claim that the approach works, but science doesn’t support the theory. Hydrating before, during and after smoking is good for your health (and for avoiding coughing fits), but it won’t get rid of bloodshot eyes.

Q: Does the red-eye thing have any connection to the fact that weed is supposed to help glaucoma patients?
A: You get a gold star. Glaucoma doesn’t just impair vision, it’s also painful. When THC widens capillaries it reduces “interocular pressure,” the primary source of glaucoma pain.


Zou, S., & Kumar, U. (2018). Cannabinoid receptors and the endocannabinoid system: signaling and function in the central nervous system. International journal of molecular sciences, 19(3), 833. [1]

Yazulla, S. (2008). Endocannabinoids in the retina: from marijuana to neuroprotection. Progress in retinal and eye research, 27(5), 501-526. [2]

Echeverri, D., Montes, F. R., Cabrera, M., Galán, A., & Prieto, A. (2010). Caffeine’s vascular mechanisms of action. International journal of vascular medicine, 2010