Cannabis and Alcohol: What Really Happens When You Mix Them

Why “Crossfading” Deserves a Closer Look

Here’s a stat that might surprise you: according to a national survey, roughly 70% of cannabis consumers also drink alcohol at least occasionally, and a significant portion report using both substances on the same occasion [Subbaraman & Kerr, 2015]. It’s so common that it has its own slang—“crossfading”—yet most people have only a vague sense of what’s actually happening inside their bodies when they combine these two substances.

This isn’t a lecture about what you should or shouldn’t do on a Friday night. This is a science article. And the science here is genuinely fascinating—and genuinely important. Because when cannabis and alcohol meet inside your body, they don’t simply add their effects together like stacking blocks. They interact. They change how each other is absorbed, metabolized, and experienced. In some cases, the combination amplifies effects in ways that can catch even experienced consumers off guard.

In this deep dive, we’ll walk through the pharmacology of what happens when THC and ethanol share your bloodstream. We’ll look at the research—both the well-established findings and the emerging questions that scientists are still untangling. And we’ll translate all of that into practical, actionable knowledge you can actually use.

By the end, you’ll understand:

• Why alcohol can dramatically increase THC blood levels
• How the order you consume matters more than you think
• What “greening out” actually is at a biological level
• How to make more informed choices if you do combine them

Let’s get into it.

The Science: How THC and Alcohol Interact

How Alcohol Changes THC Absorption

Let’s start with the single most important finding in this field, because it’s the one that has the most direct impact on your experience.

Alcohol may significantly increase the amount of THC that enters your bloodstream.

In a controlled study, researchers gave participants either a low dose of alcohol or a placebo drink, followed by inhaled cannabis. The group that drank alcohol first showed substantially higher plasma THC concentrations than the group that didn’t drink [Lukas et al., 1992]. A later study confirmed this with more precision: even a modest amount of alcohol—equivalent to roughly one to two standard drinks—increased peak THC blood levels by an average of approximately twofold [Hartman et al., 2015].

Think of it like this: imagine THC is trying to get through a controlled doorway into your bloodstream. Normally, your body’s metabolic processes act as a kind of regulator, controlling the flow. Alcohol appears to affect gastrointestinal motility and vasodilation—relaxing blood vessels and changing how quickly substances move through your digestive system, which in turn may allow more THC to be absorbed more rapidly [Lukas & Orozco, 2001].

This is why someone who can comfortably handle a particular dose of cannabis might find that same dose overwhelming after a couple of drinks. It’s not just that you “feel” it more subjectively—you may literally have more THC circulating in your blood.

The Reverse Direction: Does Cannabis Change Alcohol’s Effects?

Here’s where it gets more nuanced. While alcohol likely boosts THC levels, cannabis’s effect on alcohol absorption appears to work in the opposite direction—at least in some studies.

Research suggests that THC may actually slow gastric emptying, meaning food and liquids (including alcohol) stay in your stomach longer before being absorbed [McCallum et al., 1999]. Some studies have found that cannabis use was associated with lower blood alcohol concentrations (BAC) compared to alcohol use alone [Lukas & Orozco, 2001].

On the surface, that might sound like good news. But here’s the catch: lower BAC does not necessarily mean less impairment. The combined effect of cannabis and alcohol on cognitive function, reaction time, and motor coordination appears to be additive or even synergistic—meaning the impairment from combining them is greater than what you’d expect from either substance alone [Ramaekers et al., 2004].

In other words, you might “feel” less drunk while actually being more impaired. This is a particularly concerning combination when it comes to driving or any activity requiring coordination and judgment.

The Endocannabinoid System Meets Ethanol

To really understand why these two substances interact so powerfully, we need to zoom into the endocannabinoid system (ECS)—the same system that cannabis activates.

Your ECS is a vast signaling network of CB1 and CB2 receptors spread throughout your brain and body. THC produces its effects primarily by binding to CB1 receptors in the brain. Here’s the key insight: alcohol also interacts with the endocannabinoid system, even though it’s not a cannabinoid.

Research suggests that chronic alcohol exposure can alter endocannabinoid signaling—changing the density of CB1 receptors and the levels of your body’s own endocannabinoids like anandamide and 2-AG [Basavarajappa & Hungund, 2002]. Acute alcohol consumption appears to increase endocannabinoid release in certain brain regions, which may partly explain why alcohol produces some cannabis-adjacent effects such as relaxation, altered perception, and reduced inhibition.

When you add THC on top of an already-stimulated endocannabinoid system, you’re essentially flooding a system that’s already running elevated. This is one proposed mechanism for why the combination can feel so much more intense than either substance alone [Parsons & Hurd, 2015].

What “Greening Out” Actually Is

If you’ve ever seen someone—or been someone—who got pale, sweaty, nauseous, and dizzy after combining cannabis and alcohol, you’ve witnessed what’s colloquially called “greening out.”

While not a formal medical term, greening out appears to involve a cascade of physiological events:

1. THC-induced hypotension: Cannabis can lower blood pressure, particularly when standing (orthostatic hypotension) [Jouanjus et al., 2017]
2. Alcohol-enhanced THC levels: As discussed, alcohol may increase THC absorption, potentially intensifying this blood pressure effect
3. Vasovagal response: A sudden drop in blood pressure can trigger your vagus nerve, causing nausea, sweating, dizziness, and sometimes fainting
4. Nausea amplification: Both substances independently affect the brain’s emetic (vomiting) centers, and together they may overwhelm the system

This is why greening out is far more commonly reported when cannabis and alcohol are combined than when either is used alone. It’s also why the order of consumption matters—which brings us to practical implications.

Practical Implications

Order Matters: “Beer Before Bong” vs. “Bong Before Beer”

There’s an old saying: “Beer before grass, you’re on your ass. Grass before beer, you’re in the clear.” Like many folk wisdoms, there’s a kernel of truth here, though it’s an oversimplification.

Drinking alcohol before consuming cannabis is the combination most likely to lead to greening out or unexpectedly intense effects. This is directly supported by research showing alcohol may increase THC absorption [Hartman et al., 2015]. If you drink first and then consume your usual cannabis dose, you may experience significantly stronger effects than you’re prepared for.

Consuming cannabis before drinking may slow alcohol absorption (due to delayed gastric emptying), but this doesn’t make the combination safer—it may simply delay the onset of alcohol’s effects, potentially leading you to drink more than intended before feeling the full effect [Lukas & Orozco, 2001].

The bottom line: If you choose to combine cannabis and alcohol, the most important harm-reduction strategy is to significantly reduce your dose of both substances—not just one.

How High Families Can Inform Smarter Choices

If you do choose to consume cannabis on an occasion where alcohol is present, understanding terpene profiles may help you anticipate the character of the experience. Strains in the Relaxing High family—those rich in myrcene—tend to produce sedative, body-heavy effects that may compound alcohol’s depressant properties more intensely. Meanwhile, strains in the Balancing High family, with their gentler, lower-terpene profiles, may offer a less overwhelming starting point for those who want to be cautious.

This isn’t to say any High Family is “safe” to combine with alcohol—the interaction happens at the cannabinoid level regardless of terpene profile. But understanding your strain’s character can help you anticipate whether the experience might lean more sedating or stimulating, and plan accordingly. Newer consumers in particular may want to consult a beginner’s guide to cannabis dosing before mixing substances.

Practical Harm-Reduction Strategies

Based on the available research, here are evidence-informed strategies for those who choose to combine cannabis and alcohol:

• Start low, go slow—with both. Reduce your typical dose of each substance by at least half. The interaction means your “normal” dose may no longer produce a normal effect.
• Hydrate consistently. Both substances can contribute to dehydration, and dehydration worsens the dizziness and nausea associated with greening out.
• Eat beforehand. Food in your stomach slows the absorption of alcohol and may help moderate the intensity of the combination.
• Choose one to be primary. Rather than going heavy on both, decide which substance you want to be the main feature and keep the other minimal.
• Know your exit plan. If you start feeling unwell—dizzy, nauseous, clammy—sit or lie down immediately, sip water, and get fresh air. Most greening-out episodes resolve on their own within 30–60 minutes.
• Never drive. The research on combined impairment is unambiguous: combining cannabis and alcohol impairs driving ability far more than either substance alone [Hartman et al., 2015; Ramaekers et al., 2004].

A Note on Long-Term Combined Use

While most research has focused on acute (single-session) interactions, emerging studies are beginning to examine the effects of regular co-use over time. Some research suggests that people who regularly combine cannabis and alcohol may consume more of both substances than those who use either alone, and may face compounded risks to liver health, cognitive function, and mental health [Weinberger et al., 2016]. A 2024 study in the Journal of Cannabis Research found that simultaneous alcohol and cannabis use (SAM) was significantly associated with higher rates of cannabis-related problems compared to concurrent use that didn’t overlap in timing [Zhu et al., 2024]. This is an area where the science is still developing, and more longitudinal research is needed.

Key Takeaways

• Alcohol may significantly increase THC blood levels, potentially doubling your effective dose—even after just one or two drinks [Hartman et al., 2015]
• Combined impairment appears greater than the sum of its parts: you may feel less drunk but be more impaired in coordination, reaction time, and judgment [Ramaekers et al., 2004]
• “Greening out” is far more likely when cannabis and alcohol are combined, due to compounded effects on blood pressure and the endocannabinoid system
• Order matters: drinking before cannabis use is generally the riskier sequence, but no order makes the combination risk-free
• Dose reduction is the most important harm-reduction tool—if you combine them, use significantly less of each than you normally would

FAQs

Is it dangerous to mix cannabis and alcohol?

While the combination is unlikely to be life-threatening for most healthy adults in moderate amounts, it significantly increases the risk of unpleasant effects like nausea, dizziness, and fainting (greening out), and substantially impairs coordination and judgment. The risk appears to increase with higher doses of either substance.

Does cannabis make you less drunk?

Some research suggests THC may slow alcohol absorption, potentially resulting in lower blood alcohol levels [Lukas & Orozco, 2001]. However, this does not mean less impairment—studies consistently suggest that cognitive and motor impairment is greater when the two are combined, regardless of BAC readings.

Why do edibles and alcohol seem like an especially bad combination?

Edibles are metabolized through the liver, producing 11-hydroxy-THC, a metabolite that is generally considered more potent and longer-lasting than inhaled THC. Alcohol is also processed by the liver and may compete for the same metabolic enzymes, potentially altering the metabolism of both substances in unpredictable ways. The delayed onset of edibles also makes it harder to gauge your total level of intoxication in real time.

Can I build a tolerance to the combined effects?

Regular co-users may develop some tolerance to certain effects over time, but tolerance to impairment is unreliable and highly individual. Relying on perceived tolerance is risky, especially for activities like driving where even small decrements in reaction time matter.

Sources

• Subbaraman, M.S. & Kerr, W.C. (2015). “Simultaneous versus concurrent use of alcohol and cannabis in the National Alcohol Survey.” Alcoholism: Clinical and Experimental Research, 39(5), 872–879. PMID: 25872596
• Lukas, S.E., Benedikt, R., Mendelson, J.H., Kouri, E., Sholar, M., & Amass, L. (1992). “Marihuana attenuates the rise in plasma ethanol levels in human subjects.” Neuropsychopharmacology, 7(1), 77–81. PMID: 1326277
• Hartman, R.L., Brown, T.L., Milavetz, G., Spurgin, A., Gorelick, D.A., Gaffney, G., & Huestis, M.A. (2015). “Cannabis effects on driving lateral control with and without alcohol.” Drug and Alcohol Dependence, 154, 25–37. PMID: 26190049
• Lukas, S.E. & Orozco, S. (2001). “Ethanol increases plasma Delta(9)-tetrahydrocannabinol (THC) levels and subjective effects after marihuana smoking in human volunteers.” Drug and Alcohol Dependence, 64(2), 143–149. PMID: 11543984
• Ramaekers, J.G., Robbe, H.W., & O’Hanlon, J.F. (2004). “Marijuana, alcohol and actual driving performance.” Human Psychopharmacology, 15(7), 551–558. PMID: 12404546
• Basavarajappa, B.S. & Hungund, B.L. (2002). “Neuromodulatory role of the endocannabinoid signaling system in alcoholism: an overview.” Prostaglandins, Leukotrienes and Essential Fatty Acids, 66(2–3), 287–299. PMID: 12052043
• Parsons, L.H. & Hurd, Y.L. (2015). “Endocannabinoid signalling in reward and addiction.” Nature Reviews Neuroscience, 16(10), 579–594. PMID: 26373473
• Weinberger, A.H., Platt, J., Goodwin, R.D. (2016). “Is cannabis use associated with increased risk of onset and persistence of alcohol use disorders? A three-year prospective study among adults in the United States.” Drug and Alcohol Dependence, 161, 363–367. PMID: 26905944
• Zhu, Y., Ye, Y., Greenfield, T.K. & Kerr, W.C. (2024). “Associations between simultaneous use of alcohol and cannabis and cannabis-related problems in 2014–2016: evidence from the Washington panel survey.” Journal of Cannabis Research, 6, 8. https://doi.org/10.1186/s42238-024-00217-z
• Bedillion, M.F., Blaine, S.K., Claus, E.D. & Ansell, E.B. (2024). “The effects of simultaneous alcohol and cannabis use on subjective drug effects: A narrative review across methodologies.” Alcohol, Clinical and Experimental Research, 48(6), 988–999. https://doi.org/10.1111/acer.15322