What is theanine with caffeine for?

For tasks that require switching attention. With 100 mg of theanine and 50 mg of caffeine, the combination improved speed and accuracy in an attention-switching task and reduced distraction in a memory task, more than caffeine alone did.

Does theanine make you sleepy?

It is not a sedative and does not induce sleep. What was measured with 200 mg a day for four weeks is an improvement in subscales of the sleep quality index, including latency. That is different from taking something to fall asleep.

How much theanine should you take?

100 mg with caffeine if you are after the cognitive side, or 200 mg a day if you are after stress and sleep. Those are the doses from the two trials, and there is no reason to go higher.

Can you get it from drinking tea?

Not in the trial amounts. A cup of tea provides quite a bit less than the 100 mg of the studied combination, so reaching the dose by drinking tea would mean an amount of caffeine that no longer resembles the trial.

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L-theanine · Moderate evidence

What L-theanine is for and what it does

The short answer. L-theanine is an amino acid from tea that appears in almost no other food. It is not a sedative or an anxiolytic: what has been measured is that it lowers stress scores and improves sleep somewhat when taken daily, and that combined with caffeine it improves attention tasks more than caffeine does alone. That second use explains why it is in half of all pre-workouts: it does not take away caffeine’s effect, it takes the edge off it.

There are studies in favour, but few, with small samples or measuring markers instead of outcomes. No figure on this page is attributed to a specific product: the effect belongs to the ingredient and every number carries its source next to it.

01 What it does and how much

Each row is a measured effect, with the figure the study gives and the source number. Where the evidence gives no figure, the column says so instead of making up a percentage.

Effects of theanine with their source
Effect	How much	Detail
Attention combined with caffeine	faster and more accurate	With 100 mg of theanine and 50 mg of caffeine, the combination improved speed and accuracy in an attention-switching task at 60 minutes and reduced distraction in the memory task at 60 and 90 minutes. Caffeine alone improved subjective alertness, and accuracy only at 90 minutes. [2]
Stress-related symptoms	lower at 4 weeks	With 200 mg a day in a double-blind crossover trial with 30 healthy adults, scores fell on the self-rating depression scale, trait anxiety and the Pittsburgh Sleep Quality Index. [1]
Sleep quality	improves in three subscales	Sleep latency, sleep disturbance and use of sleep medication improved versus placebo within the same index. It is not a hypnotic: it does not induce sleep, it changes how sleep is scored. [1]
Verbal fluency and executive function	improve	In the same trial, with the caveat that the verbal fluency improvement was concentrated in those who started with lower scores. [1]
Trial size	27 and 30 subjects	This is the limit of this evidence: well-designed but small crossover trials, not meta-analyses of thousands of people. That is why this page rates it medium, not high. [1][2]

02 How to take it

Dose. 100 mg with caffeine for the cognitive side, or 200 mg a day for stress and sleep.
When. With caffeine, if the goal is attention. Daily, if the goal is stress or sleep.
How long before you notice it. The effect with caffeine is measured at 60 minutes. The stress and sleep effect, at four weeks.

Details that change the result

The usual ratio in pre-workouts and in popular advice is 2 parts theanine to 1 part caffeine. The trial that measures it best used 100 mg of theanine with 50 mg of caffeine, exactly that ratio.
It does not cause sleepiness or sedation. Anyone taking it expecting to fall asleep is buying the wrong product: that is what melatonin is for, with different evidence and different regulation.
A cup of tea provides quite a bit less than 100 mg, so the trial dose is not reached by drinking tea.
It is one of the few pre-workout ingredients with a direct trial behind it. Most of the other filler ingredients do not have one.

03 When it makes sense and when it does not

Worth it if

When taking caffeine and wanting the attention benefit with less jitteriness: its best-measured use.
Stressful periods with poor sleep, at 200 mg a day, knowing the trial is small.
Work or training that requires frequently switching focus, the specific task that improved.

Not worth it if

Looking for a sleeping pill: it does not induce sleep.
Expecting an effect on strength, muscle or endurance, where nothing has been measured.
Paying for very high doses: the trials use 100 and 200 mg, not half a gram.

04 Sources

Every figure above comes from here. They are position stands from scientific societies, meta-analyses and peer-reviewed reviews: if a claim cannot hang from one of these lines, it is not on the page. References are cited in their original form.

Hidese S et al. Effects of L-Theanine Administration on Stress-Related Symptoms and Cognitive Functions in Healthy Adults: A Randomized Controlled Trial. Nutrients. 2019;11(10):2362. Treinta adultos sanos, diseno cruzado doble ciego, 200 mg/dia durante 4 semanas: descenso en la escala de depresion autoaplicada, la ansiedad rasgo y el indice de calidad de sueno de Pittsburgh, y mejora de fluidez verbal y funcion ejecutiva. doi:10.3390/nu11102362
Owen GN, Parnell H, De Bruin EA, Rycroft JA. The combined effects of L-theanine and caffeine on cognitive performance and mood. Nutr Neurosci. 2008;11(4):193-198. Veintisiete participantes: 50 mg de cafeina con 100 mg de L-teanina mejoro velocidad y precision en la tarea de cambio de atencion a los 60 minutos y redujo la susceptibilidad a la distraccion a los 60 y 90 minutos. doi:10.1179/147683008X301513

This is not medical advice. It is what some studies say about an ingredient, not a protocol for you. With an illness, medication or pregnancy involved, the decision belongs to a healthcare professional who knows you.

Questions about theanine

Answered with the data on this page

What is theanine with caffeine for?: For tasks that require switching attention. With 100 mg of theanine and 50 mg of caffeine, the combination improved speed and accuracy in an attention-switching task and reduced distraction in a memory task, more than caffeine alone did.
Does theanine make you sleepy?: It is not a sedative and does not induce sleep. What was measured with 200 mg a day for four weeks is an improvement in subscales of the sleep quality index, including latency. That is different from taking something to fall asleep.
How much theanine should you take?: 100 mg with caffeine if you are after the cognitive side, or 200 mg a day if you are after stress and sleep. Those are the doses from the two trials, and there is no reason to go higher.
Can you get it from drinking tea?: Not in the trial amounts. A cup of tea provides quite a bit less than the 100 mg of the studied combination, so reaching the dose by drinking tea would mean an amount of caffeine that no longer resembles the trial.

And now, which to buy

Prices, kept apart from the evidence

This page explains what theanine does and deliberately names no brand. The comparison is the other half: 18 products from 4 stores from €0.122 per capsule, sorted by price and by how verifiable their certification is.

See the l-theanine comparison

Other guides

What each supplement does, with its sources