L-Theanine and Alcohol: Is It Safe to Take Them Together?

L-theanine and alcohol have not been tested together in human trials: I found no human trial of the pair, no documented dangerous interaction, and no evidence that L-theanine protects you from alcohol. The bigger safety issue is caffeine, because many L-theanine products, including our Caffeine 2.0 + L-Theanine, also contain it, and caffeine can make you feel less drunk than you are without lowering your blood alcohol.

Here is what the research shows, why the caffeine matters more than the L-theanine, and what I advise as a physician.

L-theanine vs caffeine with alcohol: what is known

The two ingredients in a caffeine and L-theanine capsule behave very differently around alcohol, and the evidence behind each is very different too.

The L-theanine column rests on animal studies. The caffeine column rests on human studies, and it points to a real risk.

Does L-theanine interact with alcohol?

No interaction has been documented in people. What exists is a small set of animal and cell studies, most of them asking whether L-theanine can soften alcohol-related damage to the liver or gut.

• 2005, mice. Researchers in Japan gave mice a single dose of alcohol by mouth, with or without theanine injected into the abdomen. One hour later, blood alcohol was lower in the theanine groups, and the liver enzymes that break down alcohol were more active.
• 2011, cells and mice. In liver cells grown in a dish, L-theanine reduced damage from alcohol. In mice given alcohol, pretreatment with L-theanine reduced the rise in the liver enzymes ALT and AST, liver fat and a marker of oxidative stress.
• 2024, mice. In mice given alcohol to cause acute liver injury, L-theanine lowered blood levels of alcohol and acetaldehyde, a toxic breakdown product of alcohol, and reduced liver damage markers.
• 2025, mice and rats. Two studies from the same university tea research lab gave animals L-theanine for four to eight weeks before alcohol exposure and reported less damage to the gut lining.

These findings are interesting, but they do not tell you what happens when a person has a glass of wine after a capsule. The animals received doses chosen for research, in the 2005 study by injection rather than by mouth, and findings in rodents need to be confirmed in people before anyone acts on them. These studies looked at liver and gut markers, not at coordination, judgment or how drunk a person feels. Until a human trial exists, the accurate answer is that L-theanine has not been shown to change how alcohol affects you.

Can you take L-theanine with alcohol?

For L-theanine on its own, no dangerous interaction with alcohol has been reported. But no evidence of harm is not the same as evidence of safety, and this pair has simply not been studied in people. For the wider picture on tolerability, see our guide to L-theanine side effects.

The practical concern is drowsiness. L-theanine is studied for relaxation: in a small 2019 crossover trial of 30 adults in Japan, self-rated stress-related symptoms and sleep quality scores improved during four weeks of 200 mg a day, but compared with placebo only a few sleep measures improved significantly more, and two of the authors worked for an ingredient company. Alcohol is a sedative. Nobody has tested whether the two together make people sleepier, but it is reasonable to assume the relaxing effects could add up.

That leads to the one rule with no exceptions: never drive, ride a bike or operate machinery after drinking, whatever supplements you have taken. L-theanine does not make you a safer driver after alcohol, and as the next section explains, caffeine can make you feel like a safer driver than you are.

Does caffeine make you less drunk?

No. Caffeine does not lower blood alcohol, and it can hide how impaired you are. The CDC states that caffeine does not reduce the effects of alcohol on your body. It adds that caffeine may make you feel like the alcohol is affecting you less, which could lead you to drink more and become more impaired. Human lab studies show the same pattern:

• 2006, 26 volunteers. In a Brazilian study, young healthy volunteers drank vodka alone, an energy drink alone, or both together. The energy drink did not change breath alcohol. People reported feeling that their coordination was less impaired with the combination, yet the energy drink did not significantly reduce the loss of motor coordination and reaction time that alcohol caused.
• 2006, 12 social drinkers. In a University of Kentucky lab study, caffeine (2 or 4 mg per kg of body weight) taken with alcohol counteracted the slowing alcohol caused on a two-task reaction test but had no effect on the extra errors alcohol caused. Participants also rated themselves as less intoxicated than with alcohol alone.
• 2011, 18 adults. In a placebo-controlled study of nine men and nine women, an energy drink mixed with alcohol did not reduce alcohol impairment of information processing or motor coordination, but it reduced feelings of mental fatigue and increased feelings of stimulation. The authors warned that drinkers may wrongly believe they can function better than they can.
• 2016, 26 social drinkers. In a double-blind, placebo-controlled study, energy drink mixers raised ratings of desire for more alcohol beyond the same amount of alcohol alone.

These studies used energy drinks or regular caffeine, not d9-caffeine, and all were small. But d9-caffeine is still caffeine, and the product page says to count it as caffeine when tracking daily stimulant intake. Feeling sharper while still being impaired is exactly the situation the CDC warns can lead to more drinking and more impairment.

How long after L-theanine can I drink?

No study has set a safe waiting time for L-theanine on its own, so there is no evidence-based number to give you. With Caffeine 2.0 + L-Theanine, the caffeine is the part to plan around.

d9-caffeine is caffeine with nine hydrogen atoms replaced by deuterium, and the liver clears it more slowly. In a 2022 industry-funded study of 20 healthy adults, a single dose of d9-caffeine produced four to five times the total exposure of a matched dose of regular caffeine. Our guide to what d9-caffeine is explains how that works.

That longer action is part of what makes the capsule useful for daytime focus, and it is also why the label already says to avoid late-day doses. A capsule taken in the afternoon may still be active in the evening. So here is my plain advice: do not use Caffeine 2.0 + L-Theanine to offset drinking, to sober up, or to stay out longer. On a day you drink alcohol, take your capsule earlier in the day, since the label says to avoid late-day doses, and do not take extra capsules later in the day.

Stay within the label maximum of 90 mg of d9-caffeine (4 capsules) a day. For general daily limits, see our guide to how much caffeine is too much.

Is L-theanine good for a hangover?

No. L-theanine is not a hangover remedy, and we do not describe it as one. I found no human trial in PubMed testing L-theanine for hangover symptoms. The lower blood alcohol seen in some mouse studies has never been shown in people, and even if it were, it would tell us nothing about how a person feels the next morning.

Hangover products in general have weak support. A 2005 systematic review in the BMJ of eight randomized trials found no compelling evidence that any conventional or complementary remedy prevents or relieves hangover, and concluded that the most effective way to avoid hangover symptoms is not drinking or drinking in moderation. A 2022 review of 21 placebo-controlled trials with 386 participants rated the evidence for every remedy studied as very low quality.

If you often wake up feeling unwell after drinking, the most useful step is a conversation with your physician about how much you drink, not another supplement.

Who should check with a physician first

Talk to your physician before combining any supplement with alcohol, and check before taking Caffeine 2.0 + L-Theanine at all, if any of these apply:

• You are pregnant or breastfeeding, or sensitive to caffeine. Caffeine 2.0 + L-Theanine is not for children, pregnant or breastfeeding individuals, or people sensitive to caffeine.
• You take medication that can cause drowsiness, such as sleep aids, sedatives or some pain medications.
• You take stimulant medication, blood pressure medication or any other prescription medication. Your pharmacist can also check for interactions.
• You have a heart condition, high blood pressure, an arrhythmia, liver disease or a sleep disorder.
• You have found it hard to control how much you drink, or someone close to you has raised concerns. Your physician can help, and the SAMHSA National Helpline at 1-800-662-4357 is free and confidential.

How Vita Bloom fits

Caffeine 2.0 + L-Theanine is a daytime product for calm, focused energy, with 22.5 mg of Deura9® d9-caffeine and 50 mg of L-theanine in each Caffeine 2.0 + L-Theanine capsule. It is not a hangover product, and it is not meant to offset alcohol. Start with one capsule to gauge your response, take no more than four a day (90 mg of d9-caffeine), and avoid late-day doses.

Frequently asked questions

Can you drink on L-theanine?

No study in people has tested it, and no dangerous interaction with L-theanine alone has been reported. It has not been shown to protect you from alcohol, the relaxing effects could add up, and you should never drive after drinking.

Does L-theanine lower blood alcohol?

It did in some mouse studies, including one in which theanine was injected. No human study has tested it, so do not rely on it to lower your blood alcohol or help you sober up.

Does caffeine sober you up?

No. In a 2006 study, an energy drink did not change breath alcohol, and the CDC says caffeine does not reduce the effects of alcohol on your body. It can make you feel more alert than you are, which is what makes the mix risky.

Can I take Caffeine 2.0 + L-Theanine on a day I drink alcohol?

Do not use it to offset drinking or to stay up later. Take it earlier in the day and avoid late-day doses, as the label directs.

Deura9® is a registered trademark of Lennham Pharmaceuticals, Inc. under exclusive license to d9 Designs Inc.

These statements have not been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure, or prevent any disease.