l theanine side effectsAre you using l theanine? Or are you thinking of buying it as a supplement against anxiety, to increase your focus or just for the general ‘calmness’ effect? Whatever your reason for taking l theanine, you’re probably curious about the l theanine side effects…

  • “Does l theanine have any side effects?”
  • “Can I safely take l theanine every day?”
  • “What is the maximum theanine dosage?”

If you’re curious about the answers to these questions – continue reading…

NOTE: these l theanine side effects are what I personally experienced during my 3+ years of using l theanine. In the literal sense of the word ‘side effects’ – L theanine has none. However, there can be some adverse effects. None of these effects are bad for your health, but they can be problematic in certain situations.

2 types of L theanine side effects

Before we discuss the l theanine side effects, I want to be make a general disticntion in side effects. This is a ditinction that goes for literally any supplement.

Here are the two categories of supplement side effects:

  • Side effects that are bad for your health – things like increased blood pressure, harm to cells and everything that damages something in your body.
  • Side effects that can be  problematic in certain situations –  by this I mean for example sleepiness. being sleepy is not a bad thing, but it can be a problem if you have to drive somewhere.

Now that get the point, let’s dive into the l theanine side effects!

There are no serious side effects

Research is very clear on this. L theanine has no side effects thata re dangerous to your health.

Heck, Japan even has a law which states that every company can put as much theanine as they want in the drinks they produce.

Even green tea contains theanine (hence its name). And green tea is one of the most healthy beverages you can drink.

Theanine has been around for hundrds of years – and there are no bad side effects.

Even theanine in powder form  people have been using it for years. Many governments in the world consider theanine to be safe.

So in short: theanine has no side effects that can be abd for your health. On the contrary, many governments find theanine very safe and it can be beneficial to your health.

However – there can be ‘bad’ effects

Having said all these amazing positives word about the non-existent l theanine side effects, I do want to talk briefly about the effects that can be bad in certain sitations:

Loss of effectiveness

One thing that I (and many other users) have found about l theanine, is that if you use it for many days in a row, it tends to be less effective.

Now, there are hundreds of people who use theanine every day (mainly those who use it to combat anxiety), so there remains an effect.

But, when taking it for general focus and productivity, theanine tends to work less effective when you’ve taken it for 4-5 days.

If you just take it once a while, the effect stays ‘new’, and you will really feel a difference.

but when you take it every day, theanine effect starts to become the normal.

Later on I’ll explain to you what the optimal usage is of l theanine!

Too calm

The focus and productivity gains tend to become smaller if you use theanine every day. However, the benefits for calmness remain.

And for some people (like me), it actually becomes too much of a good thing.

Here’s why: you see, I don’t have any anxiety issues. I don’t need anything to live a happy calm life. I’m pretty calm and secure in general.

But when I take theanine for 4+ days in a row… I tend to become really calm. Almost a little bit apathetic to life.

So, if you’re anything like me in this regard (don’t need anything to be calm), then theanine can be too much of a good thing.

If you suffer from anything anxiety related, please disregard everything I just said in this paragraph. Then you can take l theanine without any problems whatsoever (there are actually thoudsands of people worldwide using theanine to combat their anxiety problems)

You can read my article about l theanine and anxiety here.

But if you’re taking l theanine for a focus and productivity reason – use it a couple times a week max (preferrably on non consective days!)


The next thing that can happen is when you take a large dose of theanine. Now, nothing bad will happen – but you might feel sleepy.

Obviously, a supplement that makes you feel sleepy is great in many cases!

However, if you’re planning on having a productive day by taking l theanine in the morning, then being sleepy is the last thing you want.

Or when you still have to drive, taking large doses of theanine is a bad idea.

If you start to fee sleepy after taking taking theanine, try the following two solutions:

  • Next time, take less theanine. Try reducing your dose in half and see what happens.
  • Drink a cup of coffee. Caffeine has many benefits that enhance the effect of theanine. And it’s a great tool to combat any tiredness you might feel from l theanine.

My L theanine recommendations:

Preserve its effect: take it 1-3 times per week MAX

Like I said before, if you don’t want to feel too calm. Then take theanine maximum 3 times per week and  on non consecutive days.

This will keep the effect of theanine fresh and you will get all the benefits of theanine without any negative effects whatsoever.

BUT, if you suffer from anxiety related problems – feel free to take it daily if it helps!

Take 200-400 mg per day (and 200 mg max per serving)

If you don’t want to feel sleepy with theanine, then I recommend you take 200-400 mg theanine maximum per day. I do not recommend taking more than 200 mg in one serving, since it doesn’t add any extra benefits.

Taking 100-200 mg is enough to reap all the positives (more doesn’t add anything – just makes you more sleepy).

You can take it twice per day for focus enhancing effects.

However, if you want a dose that will put you to sleep, than you can take anything between 200-500 mg, depending on how well your body reacts to theanine!

L theanine side effects – Final words

L theanine has no side effects that are bad for you health. It is actually a good thing for your body since it makes you less stressed.

But, in certain situations, being too calm can be a bad thing. If you’re not suffering from anxiety, then regulating your theanine usage will be a good thing to keep its effect fresh!


P.S. Want to read a detailed review about theanine and all the benefits that it has to offer? Click here to read my theanine review!

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