Best L-Theanine Supplement

People who know what L-theanine is might associate it with tea.1 After all, tea is one of the most generous sources of L-theanine in nature.2 And the various benefits of drinking tea are widely known, from reducing stress to increasing lifespan.3 But what if you took L-theanine on its own instead of drinking copious amounts of tea every day?

L-Theanine supplements can impart many of the benefits you get from drinking tea, and then some, thanks to the fact they concentrate the substance into convenient capsules.4 And L-theanine supplements have been shown to help with everything from sleep and mood to cognitive health.

But which L-theanine supplement should you try? It turns out, that depends largely on what you hope to get from the supplement, as companies combine L-theanine with various other helpful ingredients to achieve specific goals. Our team tried the best options on the market to create this guide, and we’ll take you on a deep dive into the science behind L-theanine supplementation and how it relates to some stellar products.

If you’re pressed for time, here’s a brief summary of our findings:

At Innerbody Research, we comprehensively test and research every product or service we review, including the L-theanine supplements in this guide. Regarding L-theanine specifically, we read through more than 300 scholarly articles pertaining to L-theanine supplementation and the science behind sleep, cognition, mood, and other aspects of life that L-theanine may be able to improve.

As our research phase drew toward its conclusion, we scoured the market for supplements whose ingredient bills aligned with doses and regimens used in successful scientific research, then ordered those products to try for ourselves. This gives us unique insight into the customer experience that’s tempered by thoughtful research.

Additionally, like all health-related content on this website, this guide was thoroughly vetted by one or more members of our Medical Review Board for accuracy and will continue to be monitored for updates by our editorial team.

Over the past two decades, Innerbody Research has helped tens of millions of readers make more informed decisions about staying healthy and living healthier lifestyles.

In evaluating L-theanine supplements, we focused on four criteria that are the most important things you should consider when comparing different options. These criteria are effectiveness, safety, cost, and convenience. In each case, we were able to identify a clear winner from among the various products we tested, though some criteria have pretty close runners-up.

Let’s take a closer look at each category to see what products rose to the top.

Effectiveness

Winner: Thesis Confidence

When you consider an L-theanine supplement, you’ll want to ask yourself what your goals are for using it. If you want to reduce stress or increase focus, no option that we’ve found on the market would do better than Thesis Confidence. Its ingredient bill includes a well-documented 200mg dose of L-theanine along with effective doses of caffeine, ashwagandha, and saffron.5 The formula also includes a few other well-considered, if slightly underdosed, ingredients that may combine to add a little punch.

Every Thesis blend contains L-theanine and caffeine as an option in a separate capsule you can choose whether or not to include in your order. But our review of the rest of the company's formulas revealed that Confidence has the best combination of ingredients and doses that double down on L-theanine's potential benefits.

A close runner-up here would be Ritual Stress Relief, which combines three ingredients: L-theanine, ashwagandha, and saffron. If you’re interested in L-theanine for sleep support, this is actually a better choice than Thesis Confidence, as it contains no caffeine. But that lack of caffeine and a few other interesting ingredients puts Ritual a hair behind Thesis for stress relief and cognition support.

Safety

Winner: Swanson Suntheanine

To ensure a high degree of safety, it’s typically wiser to limit the number of ingredients in a supplement. Fortunately, simple L-theanine supplements are plentiful, and a branded supplement called Suntheanine presents an opportunity to get a well-researched and responsibly manufactured version of this potent amino acid.

In studies, L-theanine has shown a great safety profile, with animal studies employing doses that equate to around 50g/day in humans without any side effects.6 Another study, which combined L-theanine or placebo with the anti-anxiety medication fluoxetine, reported only mild drowsiness and occasional GI upset.7

Studies into Suntheanine bear similar results. A study from 2019 used 200mg of Suntheanine for four weeks and reported no significant adverse effects.8 And a review from 2007 considered four well-designed safety studies, all of which point toward a high degree of safety and purity in Suntheanine.9

Numerous companies offer Suntheanine as a supplement, but Swanson has the best combination of manufacturing standards, third-party testing, and a money-back guarantee.

Cost

Winner: Bulk Supplements L-Theanine Powder

As is the case with safety, cost is something you can control by selecting a single-ingredient supplement. There’s no shortage of L-theanine-only supplements out there, but Bulk Supplements has the best price per gram of the many options we reviewed.

Because Bulk Supplements sells the product in powder form, the company’s production costs are lower, and it passes those savings onto its customers. What’s more, you can buy different quantities of powder that get cheaper by the gram as the size goes up.

Here’s a quick comparison of Bulk Supplements’ prices and costs per gram of L-theanine compared to the category’s runner-up, Swanson:

As you can see, even the smallest quantity that Bulk Supplements offers (100g) is about one-fifth the cost per gram compared to Swanson. And quantities of L-theanine from Bulk Supplements go all the way up to 25kg (though it would take you nearly 350 years to consume all that at 200mg/day).

Convenience

Winner: Green Roads Stress Aways

What makes one supplement more convenient than another comes down to things like how easy it is to take, what the regimen is like, how available a company is for support, and how that company’s policies protect you and your investment.

Green Roads makes an L-theanine gummy that we highly recommend. It’s more accurate to describe it as a CBD gummy, but its CBD dose is relatively small, and it also contains ashwagandha and L-theanine. The gummies are especially easy to take thanks to a nice flavor that our testers enjoyed.

The company doesn’t have chat support, but email inquiries are answered quickly. We typically received thorough responses in under 24 hours. The phone support is superior, though. After an average of less than one minute on hold, we had sometimes complex questions answered with relative ease from company reps.

Adding to the ease of use and the good support, Green Roads offers a 30-day money-back guarantee that’s rivaled in our guide only by Swanson’s 100-day guarantee.

L-Theanine is an amino acid most commonly found in tea. In fact, much of tea’s flavor profile can be attributed to the presence of various amino acids, with L-theanine being the most abundant.42 It can also be found in some mushrooms or produced synthetically, but tea is its most common source in nature.

The “L” in L-theanine.

Technically, theanine is the amino acid in question, and L-theanine is one of two ways it exists in a bioavailable form (the other being D-theanine). L-theanine can be produced naturally or synthetically, whereas D-theanine can only be produced synthetically.10

Research indicates that D-theanine may have a vastly different and likely inferior efficacy profile compared to L-theanine. L-Theanine appears to be much more bioavailable than D-theanine, and D-theanine degrades in plasma more quickly.11 12

How is L-theanine made?

While L-theanine can theoretically be derived from natural sources, it would be an expensive process; the amino acid only makes up about 1-3% of dried tea.13 It’s far cheaper to produce it synthetically. Unfortunately, producing synthetic L-theanine typically results in roughly a 50/50 split between L-theanine and D-theanine in your final product.9 Some research indicates that the D-theanine in an evenly split supplement can suppress the efficacy of L-theanine, so if a manufacturer doesn’t take the next step to isolate the L-theanine from the D-theanine, you’ll end up with a product that could cancel itself out.10

Another way to make L-theanine is to use the process employed by Taiyo International, the company behind the patented Suntheanine L-theanine supplement. This process is designed to mimic the natural creation of theanine in tea leaves, starting with the same compounds converted to theanine within the plant: ethylamine and L-glutamine. An enzymatic process using glutaminase converts these two into L-theanine with a preference for the L form, resulting in a product that’s at least 98% L-theanine.13

It’s important to note that, while this patented form of L-theanine is popular and reliable, there are non-branded L-theanine supplements that boast similar purity. It’s imperative to check the label or ask the company to provide evidence of purity in these cases.

There’s a long list of potential benefits from L-theanine supplementation, many of which understandably overlap with benefits seen in studies on tea consumption. But L-theanine-specific studies abound, and they point to significant potential for the substance to outperform tea on its own.

Among the benefits for which L-theanine has been shown effective, you’ll find improvements in:4

• Stress
• Sleep
• Neurological health (including memory and attention)
• Longevity
• Blood flow

There’s also ample evidence that L-theanine can offset the less pleasant effects of caffeine and even work synergistically with caffeine to improve focus.14 15

Let’s take a quick look at each of these potential benefits and what research says about them:

Who is L-theanine for?

Given its relatively wide assortment of potential benefits, L-theanine could make a fine addition to many people’s supplement regimens. It would be especially good for anyone who feels a little stressed out and either doesn’t want to turn to prescription anxiolytics or is already on them and wants to improve their anxiety further without upping their prescription dose.

L-Theanine is also one of the best options on the market for improving sleep, and this is something plenty of people may need without realizing it. You could go to sleep at 10 p.m. and wake up at 6 a.m. feeling okay, but not feeling anywhere near as good as you should for having gotten eight hours of sleep. A supplement like L-theanine may improve your overall health and alertness by improving not just how long you sleep but how well you sleep.

L-Theanine is also a smart addition to the daily routines of big-time caffeine users who sometimes get a little jittery. Maybe you never drink coffee, but you have a few too many Diet Cokes in a 24-hour period. L-Theanine can balance out some of the negative effects without necessarily canceling out the focus that caffeine can provide.

Finally, an L-theanine supplement may be a boon to cognition, memory, and focus for anyone who’s starting to notice little signs that they might need help in those departments. Research is still limited, but boosts in brain performance among those with mild cognitive impairment have been shown in studies.20

Who might want to look elsewhere?

So, L-theanine sounds like it can do a lot, but it’s not a panacea, and there are certainly people who might need to look elsewhere. If you're especially susceptible to drugs or supplements that make you drowsy, L-theanine might have that effect on you. If you aren’t using it to get to sleep, that could be a nonstarter.

Also, because of L-theanine’s potential to affect blood pressure, some doctors may advise patients on blood pressure medications or those with certain conditions to steer clear. And if you have any contraindications to other ingredients included in a complex formula alongside L-theanine, that would be another reason to look elsewhere.

L-Theanine is one of the safest supplements on the market. The vast majority of studies that our team has reviewed report no significant side effects beyond the occasional headache or GI upset, both of which are incredibly common among nutritional supplements.

Of course, there are always some safety concerns when adding any new supplement to your regimen. In addition to those potentially mild side effects, some users may experience a drop in blood pressure associated with L-theanine administration. However, much of the research has illustrated that such an effect is a negation of caffeine’s ability to raise blood pressure rather than an ability of L-theanine to take a person’s blood pressure down below its normal resting state.26

Also, in some research looking at L-theanine in isolation (or, more specifically, in mango sorbet), no effect on blood pressure was observed.27

It appears that L-theanine should be mostly safe for most people, but it’s always a good idea to talk to your doctor before introducing any new supplement into your regimen.

Best L-theanine complex for cognition

Thesis is a nootropics company offering six blends targeting select areas of cognition and mental performance. All six blends contain caffeine and L-theanine by default, but the site lets you remove caffeine from any formula. Unfortunately, removing caffeine from any formula also removes the L-theanine, as the two ingredients share a capsule. That’s why Thesis didn’t get a nod for the best L-theanine complex for sleep, since the only way to get L-theanine in any Thesis formula is alongside caffeine.

That said, we regard it as the best complex for cognition because it provides ample doses of several known brain boosters, as well as small but potentially effective doses of some other great ingredients.

Here’s a quick look at the ingredient breakdown:

• Magnesium bisglycinate: 500mg
• Sage extract: 333mg
• Shoden ashwagandha extract: 120mg
• Affron saffron extract: 28mg
• Zembrin: 25mg
• DHH-B: 10mg
• Caffeine: 100mg
• L-Theanine: 200mg

We’ve covered the potential benefits of L-theanine already, so here we’ll go into detail about the other components in Confidence.

With this particular combination, you can see how well Confidence should be able to mitigate stress and anxiety without sedating you. There should also be some general cognitive benefits, as well as long-term benefits for sleep health (just not short-term ones, thanks to the caffeine).

The odd thing about Thesis is that it positions its supplements as though you could take them just one or a few days in a row and really start to feel something. The available science doesn’t bear that out. It’s true that single doses of L-theanine, caffeine, and even ashwagandha may have noticeable effects, but the effects of most of the ingredients in Thesis formulas take weeks of daily use to set in.

Despite this science, Thesis provides you with a total of 24 doses each month divided into four six-dose boxes of individual formulas. You can mix and match formulas as you see fit within this structure. That could mean getting two boxes (or 12 doses) of Confidence and one box (six doses) each of two other Thesis blends.

There’s some ingredient crossover from blend to blend, which can work toward attaining the beneficial effects associated with chronic consumption, but that’s not typically the case.

Thesis Confidence pricing

Thesis recently expanded the scope of its subscription plan to include longer-term subscriptions that save you a little more money per box. Here’s how it works out:

There are no penalties for canceling your subscription, so if you can remember to do so, starting out on a subscription plan and then canceling it is significantly cheaper than a one-time purchase.

Thesis ships all of its orders for free, and the company provides a generous 30-day money-back guarantee that, in our experience, doesn’t even require you to ship back any product you have left.

Best L-theanine complex for sleep

Ritual essentially takes three of the most potent and well-researched branded ingredients from Thesis Confidence and stops its formula right there. No promising but underdosed helper ingredients and no caffeine. The result is a supplement that is strong enough to potentially let you feel it after a single dose while supporting long-term stress relief and sleep support. In fact, in our guide to over-the-counter sleep aids, Ritual’s Stress Relief is our top choice.

There are some competing sleep supplements out there combining L-theanine and things like valerian or melatonin, but it’s our position that these represent more short-term solutions. They have a place in helping some folks get sleep now, but their use likely isn’t sustainable for most people.

Here are the ingredients in Ritual Stress Relief:

• Shoden ashwagandha extract: 80mg
• Affron saffron extract: 28mg
• Suntheanine L-theanine: 200mg

Ritual also blends these ingredients using its patented BioSeries technology, which packages three smaller time-released doses into a single capsule. The company doesn’t say how much is in each sub-capsule, but the idea is that the first one dissolves and absorbs more quickly than the other two, offering fast, palpable relief from stress. The other two break down more slowly, offering relief throughout the day.

We can’t confirm a palpable difference from testing; to us, the supplement was effective but not noticeably more so than taking the same three ingredients in regular capsules.

Ritual Stress Relief pricing

Ritual is relatively fairly priced for a supplement with these three branded ingredients in it. A one-time purchase is $60, but you can subscribe monthly for $54/month or quarterly for $153 every 90 days. That quarterly subscription ends up costing you about $51/month. It’s a simple supplement, but buying all three ingredients and taking them at this dose together would be more expensive.

Ritual offers a 30-day money-back guarantee that resembles the promise from Thesis, allowing you to try the product for a month to see if it works. It’s not as generous as Swanson’s 100-day guarantee, but it should still be enough time to see whether Stress Relief works for you.

Best L-theanine-only option

If you’re going to reach for an L-theanine supplement that contains only L-theanine, Swanson’s Suntheanine is where we recommend you start. To be clear, Swanson isn’t the maker of Suntheanine — that’s a nutraceutical company called Taiyo International — but of all the companies offering a Suntheanine-only supplement, Swanson is the best.

With a dose range running from 50mg-400mg in many studies on various L-theanine benefits, Swanson’s offering of 100mg or 200mg capsules gives you tremendous dose flexibility that can easily align with your wellness goals. The only difference between the 100mg and 200mg versions of the supplement is that the 200mg version uses white rice powder as an excipient and the 100mg version uses brown rice powder. That normally wouldn’t mean much except for the fact that the brown rice powder isn’t certified gluten-free. As a result, only the 200mg capsules are advertised as gluten-free, which excludes anyone sensitive to gluten who wants to start at a lower dose.

Fortunately, the 200mg version is an even better deal than the 100mg capsules, which are well-priced already.

Swanson Suntheanine pricing

With two capsule sizes available both as one-time purchases and as subscriptions, there are a number of ways you can get into Swanson’s Suntheanine. Here’s how the pricing works out, as well as how much each costs per gram of L-theanine powder overall:

As you can see, both supplements are very well-priced, but the cost per gram for the 200mg capsules is significantly lower.

One issue to consider with Swanson, however, is shipping costs. If you purchase enough products in a single order to reach the $29 free shipping threshold, you’ll be fine, but standard shipping on less expensive orders is nearly $10. Other companies in this guide have similar rates, but with the cost of a single bottle hovering around $10, this shipping charge almost doubles the cost of your order.

On the bright side, Swanson offers the longest money-back guarantee in our guide, giving you up to 100 days to try its products before returning them if they don’t work out for you. For just about every condition you could hope to address with L-theanine, that should be plenty of time to try it out, titrate upward as needed, and discover whether it works for you.

Best budget pick

You can typically rely on Bulk Supplements to offer well-made supplements in powder form that don’t cost too much money, especially if you’re willing to buy in larger quantities up front. Like many of its products, Bulk Supplements offers its L-theanine as a powder in six sizes, with larger quantities netting you the most savings per gram of L-theanine.

The downside of this approach is that you have to mix the powder into a beverage on your own, rather than simply taking it as a capsule. Fortunately, L-theanine doesn’t have much of a taste to it, so you can mix it into pretty much anything and not notice a big difference in the final product.

One issue worth noting, however, is that Bulk Supplements doesn’t supply you with a scoop or any other means of measuring the right dose per serving. That means you’ll need a food scale or similar implement to get the right amount of L-theanine powder into a beverage of your choice.

Pricing

Between bulk and subscription savings, you can get a great price on Bulk Supplements L-theanine. Here’s how it works out in five of the company’s six size offerings:

There’s also a 25kg drum you can order, but that’s more L-theanine than anyone could likely consume in a lifetime. Even a 100g bag would last you around 1.5 years if you took 200mg daily.

Bulk Supplements offers free shipping on orders over $59, but only the 5kg drum gets you across the threshold — far more than we recommend for any one person. That means you’re likely going to spend another $10-11 on shipping, which takes a bite out of your savings. That said, it’s still a superior deal to others, and if you purchase additional supplements from the company, you may reach that free shipping threshold more easily.

Bulk Supplements offers a 30-day refund policy for unopened items only. However, you can get a partial refund for opened products that’s equal to the price of the smallest available quantity. For example, if you bought a 250g bag of L-theanine for $22.97 and wanted to return it after opening it, Bulk Supplements would only refund you $16.97 (the cost of a 100g bag). Once you’ve paid for shipping in both directions, it may be less costly to just keep whatever you order.

Best L-theanine and caffeine combination

Nootropics Depot offers a wide range of brain-related supplements, many as individual ingredients but occasionally in complexes. The company’s Caffeine + L-Theanine is one of its targeted complexes, aiming to provide the nootropic benefits of caffeine without the negative effects that caffeine pills can cause.

Research often points toward a 2:1 ratio of L-theanine to caffeine as providing the most benefits to users, specifically an alertness from caffeine without the jitters. If you already have a sufficient caffeine ritual in the morning, this might deliver more caffeine to your daily dose than you should add, even with the included L-theanine. That said, if you want to use this in place of one or two of your daily cups of coffee or tea, the balanced dose of 100mg caffeine and 200mg L-theanine would likely be quite useful. That’s about the same amount of caffeine you’d get from a double shot of espresso.

If you’re more tolerant to caffeine, or you want this supplement to supplant your coffee- or tea-drinking habit, you could also reach for the version that contains 200mg caffeine and 100mg L-theanine. However, this would likely still result in feelings of over-caffeination and jitteriness in most people. After all, that’s equal to about four shots of espresso.

Nootropics Depot pricing

Nootropics Depot offers either balance of caffeine and L-theanine in 60- and 180-count bottles at the following prices:

As you can see, the 180-count bottles offer a much better cost per dose, and the version with more caffeine than L-theanine is a bit more expensive. None of these bottles will reach the company’s free-shipping threshold, however, which is set at $50. There are also no opportunities for subscription savings.

Unlike Swanson, Ritual, and others that have money-back guarantees, Nootropics Depot only accepts returns on unopened products. That makes it the strictest of the companies in this guide.

Best CBD with L-theanine

Cannabidiol (CBD) is an incredibly popular supplement for sleep, anxiety, and pain, making it a sensible ingredient to combine with L-theanine for people seeking relief — at least on those first two counts. In this case, the combination looks like this:

• Broad-spectrum CBD: 25mg
• L-Theanine: 100mg
• KSM-66 ashwagandha: 150mg

Delivering these doses in a gummy is something of a double-edged sword. You get the convenience and nice flavor involved with taking a sweet gummy, but you also get some unreliability in dosing. It appears that gummy doses can vary widely, not least of all because their potency degrades so much over time.43 You also have to contend with the fact that your individual digestion — right down to how effectively you chew — can alter bioavailability in ways that encapsulated ingredients avoid.

One helpful aspect of Green Roads is that the company publishes batch-specific third-party testing results, so you can see just how potent each gummy was when it was manufactured.

Our testing team can also attest to the efficacy of this product, as well as its pleasant taste. There are better-tasting CBD gummies out there, but the cherry flavor didn’t veer into anything too artificial. And our testers all found the gummies to be significantly relaxing, more so than plain CBD gummies of a similar dose. That speaks to the efficacy of the included L-theanine and ashwagandha.

Green Roads pricing

Green Roads offers its Stress Aways in two pack sizes containing either ten or 30 gummies. The 10-pack is only available as a one-time purchase, but you can subscribe to the 30-pack for added savings. Here’s how the pricing works out:

As you can see, the 30-pack is a better deal per dose, especially if you subscribe. Subscribers also get free shipping, which saves you another $10 in shipping fees.

Green Roads offers a 30-day money-back guarantee, which is nice to have with a product that can work for you after a single dose. But it’s still less than Swanson’s 100-day guarantee.

No matter your interest in L-theanine, there are viable alternatives to consider. Some are other single-ingredient supplements with scientific support behind them for specific goals. Others are complexes like the cognition and sleep formulas included in this guide. We’ll break down some interesting alternative options by intended effects so you can more easily find another option if L-theanine doesn’t fit in with your plans or needs.