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The Effects of Mixing Caffeine and Alcohol

Mixing caffeine with alcohol can be a dangerous practice. Caffeine can mask the effects of alcohol, making it harder for a person to judge when they’ve reached a dangerous level of alcohol consumption.[1] Once the caffeine wears off, a person may be significantly more impaired than they intended.

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Some of the key risks of combining caffeine and alcohol include the following:[2]

  • Cardiovascular stress
  • Impaired judgment
  • Increased risk of alcohol-related harm

The Effects of Mixing Caffeine & Alcohol

Both caffeine and alcohol act on neurochemical processes related to the neuromodulator adenosine.[3] This neurochemical helps to modulate a variety of behavioral processes. When alcohol and caffeine are used together, these two substances can have a sort of “push-pull” effect, with caffeine acting as an adenosine antagonist (decreasing the amount adenosine affecting a person) and alcohol increasing adenosine levels.[3] 

The effects of alcohol tend to be temporarily masked by caffeine use. There will be less slowing of the nervous system while caffeine’s effects are present.[1] Many people who combine these drugs develop a false sense of alertness despite their level of intoxication. 

One significant danger of this masking effect is that it greatly increases the chance that someone engages in dangerous drinking. While under the effects of caffeine, a dangerous amount of alcohol use may not feel dangerous, as the severity of its effects will be reduced. If a person then consumes more alcohol, they may risk alcohol poisoning once the caffeine begins to wear off, and they start to experience the full effects of the alcohol they consumed.[4]  

Opposing Effects

Consuming both of these substances together can have a dangerous effect on heart rate and blood pressure. Caffeine speeds up the nervous system, while alcohol slows it down. This mix of fairly extreme signals in the body can be very taxing. While experts generally recommend everyone avoid mixing caffeine and alcohol, people with heart conditions should especially avoid this combination of drugs.

It’s also worth noting these drugs don’t really synergize well, even from a recreational perspective. They essentially cancel each other out, but not in any way that is consistent or predictable enough to use this property to counteract the worst properties of either drug. It’s a dangerous combination without any real benefits.[5]

Health Risks Associated With Mixing Caffeine & Alcohol

Various factors including genetics, a person’s individual tolerance for both drugs, and personal metabolism can affect how dangerous it is to mix caffeine and alcohol. As noted earlier, some health conditions, especially those affecting the heart, can also contribute to the risk of combining these drugs.[1] 

Effects on the Heart

The excessive use of either drug has the potential to contribute to a person’s risk of stroke, heart attack, and heart disease.[6] Combining these drugs can also increase a person’s risk of developing an irregular heartbeat (atrial fibrillation). When consumed at high levels, both alcohol and caffeine can tax the heart, and combining these substances is only going to make the effect of the drugs less predictable. 

On its own, the risks of alcohol on overall health are well-documented, and mixing alcohol with caffeine can exacerbate some of these risks. The FDA has outright banned some drinks that combine caffeine and alcohol (caffeinated alcoholic beverages, or CABs), as they determined the caffeine added to them was unsafe.[7]

Effects on Sleep

Caffeine and alcohol can also contribute to sleep irregularities, although how the combination of drugs might impact sleep isn’t well-studied.[2] Caffeine can delay a person’s ability to feel sleepy. Alcohol can increase sleepiness temporarily but can then significantly affect the quality of sleep, making it less restful and/or causing a person to wake up before fully rested. 

Drug Timelines

Alcohol generally begins to affect a user within a few minutes. The body usually takes about one to two hours to process a standard drink (depending on how much one has already consumed).[8] However, the specifics of how a person processes alcohol can vary significantly. 

Caffeine can be comparably difficult to predict, even if it is typically regarded as less dangerous than alcohol. Its effects will usually take effect about an hour after consumption and can last anywhere from two to 12 hours.[9] This again emphasizes that meaningfully timing the overlap of these two drugs’ effects in any useful way isn’t something one can do reliably.  

Understanding Caffeine & Alcohol on Their Own

Caffeine is a stimulant. It binds to adenosine receptors in the brain, which stops adenosine from binding to those receptors. This neurotransmitter is involved in regulation of sleep, arousal, cognition, memory, and learning, and as such, caffeine can impact a person in all these areas.[5] Used on its own, the drug is associated with a feeling of energy and alertness.  

Alcohol is a depressant, meaning that it depresses (or slows) activity in the nervous system. When we drink alcohol, it slows down the speed at which signals travel from the brain to other parts of the body and back again.[10] This can cause a sense of euphoria, loss of coordination, worsening of judgment, and more. 

Processing alcohol is also relatively difficult for the body, taxing the liver and, in high quantities, potentially causing liver damage.[11] If consumed in high doses, alcohol can dangerously depress the nervous system, making activities like breathing more difficult or even making it impossible for a person to draw in enough air to support their body’s needs.[12] 

The Popularity of Caffeinated Alcoholic Drinks Among Young Adults

Caffeinated alcoholic beverages are popular, particularly among young adults.[13] The risks associated with these alcoholic energy drinks are more substantial than the risks of drinking alcohol alone.[14]

According to a 2017 survey, 10.6% of students in 8th, 10th, and 12th grades and 31.8% of young adults ages 19 to 28 claimed to have drunk alcohol combined with caffeine in the prior year.[5] Additionally, a different study suggested people who binge drink may be more than twice as much likely to drink alcohol mixed with energy drinks compared to people who don’t binge drink.[5]

According to the CDC, people who mix alcohol with energy drinks to have unprotected or unwanted sex, experience injuries related to alcohol use, and drive drunk or get in a car with a driver who has been drinking.[5] Put another way, the many ways in which alcohol is known to negatively impact decision-making are often worsened for people who combine alcohol and energy drinks (which contain high amounts of caffeine).

Young people who drink alcoholic energy drinks are at higher risk for the following:[4,15-17]

  • Higher levels of intoxication
  • Dehydration
  • Engaging in risk-taking behaviors
  • More severe hangovers
  • Injuries 
  • Cardiovascular issues
  • Anxiety
  • Insomnia
  • Headaches
  • Gastrointestinal issues
  • Dental issues
  • Alcohol poisoning

Don’t Mix Alcohol & Caffeine

Combining alcohol and caffeine is dangerous, especially if you have health conditions that may put you at risk for serious heart complications. Mixing these substances makes miscalculating how much you drink much easier with little benefit. 

The masking effects caffeine may have are temporary and can’t be relied upon. While you should always drink in moderation regardless, if you do drink heavily, never do so while also drinking high-caffeine drinks like energy drinks. 

Ultimately, mixing alcohol and caffeine together has a chaotic effect on the body and mind.[18] It’s an unnecessary risk and the combination of these drugs is often associated with individuals who struggle with serious alcohol problems, such as alcohol addiction. If you are unable to cut back on your drinking on your own, professional help is needed. 

If you have been drinking high levels of alcohol for a long time, you need assistance with the alcohol withdrawal process. Attempting to simply stop drinking suddenly without medical supervision can potentially result in life-threatening withdrawal symptoms, such as delirium tremens (DTs). Instead, reach out for help today. With the right assistance, you can leave alcohol abuse behind you.

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Medically Reviewed By Dr. Alison Tarlow

Dr. Alison Tarlow is a Licensed Clinical Psychologist in the States of Florida and Pennsylvania, and a Certified Addictions Professional (CAP). She has been a practicing psychologist for over 15 years. Sh... Read More

Updated May 1, 2024
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  2. Energy drinks mixed with alcohol: What are the risks? Marczinski CA, Fillmore MT. Nutrition Reviews. 2014;72:98-107.
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  6. Alcohol and caffeine synergistically induce spontaneous ventricular tachyarrhythmias: ameliorated with dantrolene treatment. Zhang Y, Kim C, Wasif N, et al. Heart Rhythm O2. 2023;4(9):549-555.
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  9. How long does it take for caffeine to wear off? Sleep Foundation. Published January 9, 2024. Accessed February 12, 2024.
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  12. Alcohol’s effects on health. National Institute on Alcohol Abuse and Alcoholism. Accessed February 12, 2024.
  13. Alcohol mixed with energy drinks: Expectancies of use and alcohol-related negative consequences among a young adult sample. Powers G, Berger L. Addictive Behaviors Reports. 2020;12:100292.
  14. Alcohol, energy drinks, and youth: A dangerous mix. Marin Institute. Accessed February 12, 2024.
  15. Alcohol mixed with energy drinks and risk of injury: A systematic review. Roemer A, Stockwell T. Journal of Studies on Alcohol and Drugs. 2017;78(2):175-183.
  16. Energy drink consumption: Beneficial and adverse health effects. Alsunni AA. International Journal of Health Sciences. 2015;9(4):468-474.
  17. Youth consumption of alcohol mixed with energy drinks in Canada: Assessing the role of energy drinks. Doggett A, Qian W, Cole AG, Leatherdale ST. Preventive Medicine Reports. 2019;14:100865.
  18. The neurophysiology of caffeine as a central nervous system stimulant and the resultant effects on cognitive function. Cureus. Published May 2021. Accessed February 12, 2024.
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