L-theanine has become a popular choice for people who want to feel more settled and focused, without reaching for a traditional sleep aid or stimulant.
It’s an amino acid found naturally in tea, particularly green tea, and is now widely available in capsules, powders and blended supplements. It’s often taken by people looking to support relaxation, sleep or focus, including those searching for the best L-theanine supplement for anxiety, ADHD or concentration, as research has explored its potential effects on cognition, mood and sleep.
Some products contain L-theanine alone, while others combine it with stimulants such as caffeine or calming additions such as magnesium or ashwagandha. L-theanine is also often seen combined with GABA, a neurotransmitter that can help reduce nerve activity, supporting relaxation and calm, according to studies.
Dose, format, serving instructions and cost per day can all vary. We’ve considered what makes the best L-theanine supplement for different needs, as well as the most suitable dose and time of day to take it.
For this guide, we tested the best L-theanine products from brands including Nature’s Best, Serenova, ESN and DR. Vegan. We also looked at products available from retailers such as Boots, Superdrug and Holland & Barrett, comparing ingredients, ease of use, taste and value for money.
For more tried-and-tested recommendations, visit our health reviews, including the best magnesium supplements, best ashwagandha supplements and best pre-workout supplements. You can also read what supplements should I take?.
Best L-theanine supplements at a glance
JUMP TO REVIEWS
- Best clean L-theanine: Cytoplan L-Theanine, £15.99
- Best L-theanine for energy: fourfive Hydro Hydration Energy and Focus Sachets, £33
- Best L-theanine for focus: ESN L-Theanine, £10.39
- Best L-theanine for sleep: DR. Vegan Vegan Nights, £17.99
- Best magnesium L-theanine supplement: Myprotein Sleep and Relax Capsules, £10
- Best L-theanine capsule: Holland & Barrett L-Theanine Capsules, £13.99
- Best dose of L-theanine: New Leaf Products L-Theanine Capsules, £11.65
- Best L-theanine for relaxation: Nature’s Best L-Theanine, £12.50
- Best ashwagandha and L-theanine supplement: Ten Percent Club Unwind and Sleep Blend, £42
- Best L-theanine supplement for kids: Viridian L-Theanine and Lemon Balm, £20.35
- Best L-theanine supplement with B12: Serenova Focus with Vitamin B12, £38
How we tested L-theanine supplements
Registered nutritionist Kerry Torrens helped us assess the evidence around L-theanine, including its potential role in focus, relaxation and sleep. To put together our edit of the best L-theanine supplements, we combined this expert nutrition input with hands-on testing from health and fitness expert Laura Forsyth.
Each supplement was taken according to the manufacturer’s instructions. We recorded how easy the capsules were to swallow, whether there was any taste or aftertaste and how practical the suggested serving was.
The Good Health by Good Food team tested products across different price points, including single-ingredient supplements and formulas containing additional nutrients. The key areas we assessed were:
- Dosage and potency: how much L-theanine was provided per serving and how clearly this was stated
- Formulation: whether L-theanine was used alone or combined with other active ingredients
- Ingredient quality: the presence of unnecessary fillers, sweeteners or artificial additives
- Ease of use: capsule size, number of capsules and suggested timing
- Dietary suitability: including vegetarian and vegan suitability where relevant
- Value for money: cost per serving compared with similar products
Jump to:
Best L-theanine supplements to buy in 2026
Cytoplan L-Theanine
Available from Cytoplan (£15.99)
Best clean L-theanine supplement
Star rating: 5/5
- Format: capsules
- L-theanine per capsule: 250mg
- Daily serving: one to two capsules
- Maximum daily dose: 500mg
- Pack size: 60 capsules / 30–60 servings
- Price per serving: 27p for one capsule or 53p for two
A substantial dose and simple formula helped Cytoplan take our top spot. Each vegan capsule provides 250mg L-theanine, with the option to take two for a 500mg serving. There is no caffeine or separate green tea extract, so it can fit into either a daytime or evening routine.
I found the single-capsule format straightforward, with no powder to measure or drink to prepare. The directions are clear: take one or two capsules daily on an empty stomach. At 27p per capsule, the price is reasonable, while the 60-capsule pack lasts up to two months. It does not include magnesium, lemon balm or other complementary ingredients, but that focused formulation is part of its appeal.
Available from:
Cytoplan (£15.99 / 60 capsules)
fourfive Hydro Hydration Energy and Focus Sachets
Available from fourfive (£33)
Best L-theanine supplement for energy
Star rating: 5/5
- Format: powder sachets
- L-theanine per serving: 200mg
- Caffeine per serving: 76mg from natural coffee extract
- Other key ingredients: five electrolytes, B vitamins, Lion’s Mane, Korean ginseng and L-citrulline malate
- Daily serving: one 4.25g sachet mixed with 500ml water
- Pack size: 30 sachets / 30 servings
- Price per serving: £1.10, or 77p for the first three subscription orders
Part hydration mix, part focus drink, fourfive is built for training and long workdays. Unlike the caffeine-free products in this test, it is clearly aimed at alertness rather than evening relaxation.
We mixed the Red Berry powder with 500ml water. The sachet was quick to prepare and handy for travel. Stevia provides sweetness, while the electrolyte blend makes it more practical than a standard L-theanine capsule when hydration is also a priority.
It is expensive if you only want L-theanine, but the broader formula and Informed Sport testing strengthen the value. Because it contains caffeine, it is best avoided late in the day. Still, the dose, testing credentials and convenient format made it our strongest focus option.
Available from:
fourfive (£33 / 30 sachets)
ESN L-Theanine
Available from Amazon (£10.39)
Best L-theanine for focus
Star rating: 4.5/5
- Format: capsules
- L-theanine per capsule: 100mg
- L-theanine source: extracted from green tea
- Daily serving: one to two capsules
- Pack size: 45 capsules / 45 standard servings
- Price per serving: 23p, or 21p with subscription
- Price for 200mg: approximately 46p
ESN’s lower-dose capsule is a practical match for coffee drinkers who want control over their L-theanine intake. One capsule provides 100mg, while two supply 200mg, making it easy to adjust the serving without buying different strengths.
The capsules require no preparation and can be taken with liquid alongside meals. We found the one-capsule starting dose particularly straightforward, although using two each day reduces the 45-capsule pack to around 22 days.
The formula is vegan, vegetarian and gluten-free, while the L-theanine is extracted from green tea. Overall the flexible dose, simple ingredient list and competitive price make it a useful option if you already have a high caffeine intake during the day.
Available from:
Amazon (£10.39 / 45 capsules)
DR.VEGAN Vegan Nights
Available from DR.VEGAN (£17.99)
Best L-theanine for sleep
Star rating: 4.5/5
- Format: capsules
- L-theanine per capsule: 50mg
- Maximum L-theanine serving: 100mg
- Other key ingredients: magnesium glycinate, glycine, griffonia, zinc, chamomile and black pepper extract
- Daily serving: one to two capsules, 30 minutes to two hours before bed
- Pack size: one pouch / supplied on a 30-day purchase cycle
- Price per day: approximately 60p, or 51p with subscription, assuming a 30-day supply
Vegan Nights is an evening blend containing L-theanine alongside other ingredients, so its L-theanine dose is modest compared with several 200mg products.
The capsules fit easily around bedtime: take one or two, with or without food, between 30 minutes and two hours before sleep. We liked the flexible dosing, vegan formulation and absence of caffeine, bulking agents and artificial additives. DR.VEGAN also states that the finished product is third-party tested.
Its considered ingredient mix and clear timing make it our best L-theanine for sleep.
Available from:
DR.VEGAN (£17.99 / 30-day purchase cycle)
Myprotein Sleep and Relax Capsules
Available from Myprotein (£10)
Best magnesium L-theanine supplement
Star rating: 4.5/5
- Format: capsules
- L-theanine per serving: 200mg
- Magnesium per serving: 200mg as magnesium bisglycinate
- Other key ingredients: lemon balm, Montmorency cherry, L-tryptophan, zinc and vitamin B6
- Daily serving: three capsules taken 30-60 minutes before sleep
- Pack size: 30 servings / 30-day supply
- Price per serving: 33p at the tested price, or 67p at the previous £19.99 price
Designed for evenings, Myprotein combines 200mg L-theanine with 200mg magnesium bisglycinate in a broader relaxation formula. The capsules remove any measuring or mixing, although taking three at once is less convenient than a single-capsule supplement. Timing is clear: take the full serving 30 to 60 minutes before sleep. We also liked that every principal active ingredient is individually quantified rather than hidden inside a proprietary blend.
At the tested £10 price, a 30-day supply costs around 33p per night, which is excellent value for a combined magnesium and L-theanine product. It is also suitable for vegetarians and vegans.
Available from:
Myprotein (£10 / 30 servings)
Holland & Barrett L-Theanine 200mg
Available from Holland & Barrett (£13.99)
Best L-theanine capsule
Star rating: 4.5/5
- Format: capsules
- L-theanine per serving: 200mg
- L-theanine source: standardised 50:1 green tea leaf extract
- EGCG per serving: 15mg
- Daily serving: one capsule with or after food
- Pack size: 60 capsules / 60 servings
- Price per serving: 23p
One capsule delivers the complete 200mg L-theanine serving, making this one of the easiest products to use consistently. Unlike formulas with an unspecified source, Holland & Barrett uses a standardised 50:1 green tea leaf extract that also supplies 15mg EGCG.
We found the one-a-day format convenient, and the 60-capsule bottle provides two months of use. It must be taken with or after food, rather than on an empty stomach.
At £13.99, each serving costs about 23p, which is competitive for a clearly standardised extract. However, this is not isolated L-theanine: it contains concentrated green tea compounds. The dose, value and simple routine make this our best L-theanine capsule.
Available from:
Holland & Barrett (£13.99 / 60 capsules)
New Leaf Products L-Theanine
Available from Holland & Barrett (£11.65)
Best dose of L-theanine
Star rating: 4.5/5
- Format: capsules
- L-theanine per listed serving: 400mg
- Vitamin B6 per serving: 4mg
- L-theanine source: green and black tea leaves
- Listed serving: two capsules
- Pack size: 120 capsules / 60 servings
- Price per serving: 19p at the tested price
Dose is the standout feature here. Two capsules provide 400mg L-theanine, one of the highest clearly stated servings in the test, alongside 4mg vitamin B6. The L-theanine is described as coming from green and black tea leaves, with no caffeine or green tea extract listed in the finished formula.
The pre-measured capsules are easier than a powder, although two are needed for the full serving. We liked the simple vegan formulation and 120-capsule bottle, which supplies 60 servings.
At the tested £11.65 price, each 400mg serving costs around 19p, making it exceptional value for the dose. The strong dose, tea-leaf source and low cost make this the best choice when quantity per serving is the priority.
Available from:
Holland & Barrett (£11.65 / 120 capsules)
Nature’s Best L-Theanine 200mg
Available from Nature’s Best (£12.50)
Best L-theanine for relaxation
Star rating: 4.5/5
- Format: capsules
- L-theanine per serving: 200mg
- L-theanine source: unfermented green tea leaves
- EGCG per serving: up to 5mg
- Daily serving: one capsule with a meal
- Pack size: 60 capsules / 60 servings
- Price per serving: 21p, or around 19p when buying two pots
Nature’s Best keeps the formulation focused, with 200mg L-theanine in one vegan capsule. No magnesium, lemon balm or other relaxation ingredients are added.
We found the once-daily capsule fit easily into a routine, and the 60-capsule pack lasts two months. It should be taken with a meal and not on an empty stomach. The product is manufactured in UK facilities operating to GMP standards.
At £12.50, each serving costs approximately 21p, or around 19p when buying two pots together. That represents strong value for a green-tea-derived 200mg dose. Its simple serving, competitive price and measured formula make it our best L-theanine for relaxation.
Available from:
Nature’s Best (£12.50 / 60 capsules)
Ten Percent Club Unwind and Sleep Blend
Available from Ten Percent Club (£42)
Best ashwagandha and L-theanine supplement
Star rating: 4/5
- Format: capsules
- L-theanine per serving: not stated
- Other key ingredients: ashwagandha, Montmorency cherry, bacopa, zinc and black pepper extract
- Daily serving: three capsules
- Pack size: 90 capsules / 30 servings
- Price per serving: £1.40, or £1.12 with subscription
- Dietary suitability: vegan and gluten-free
Ashwagandha gives this blend a different focus from straightforward L-theanine capsules. The three-capsule serving also contains Montmorency cherry, bacopa, zinc and black pepper extract, creating a caffeine-free formula intended for relaxation and sleep rather than daytime alertness.
We found the capsule format simple enough to use, and the serving can be taken together or split across the day. Informed Sport certification is a valuable extra for competitive athletes.
This remains the clearest ashwagandha and L-theanine combination tested however the three capsules per day might make this less simple for everyday use.
Available from:
Ten Percent Club (£42 / 90 capsules)
Viridian L-Theanine and Lemon Balm
Available from Viridian (£20.35)
Best L-theanine supplement for kids
Star rating: 4/5
- Format: capsules
- L-theanine per listed two-capsule serving: 200mg
- Lemon balm extract per listed two-capsule serving: 300mg
- Lemon balm specification: 5:1 extract, standardised to 5% rosmarinic acid
- Children’s serving: one capsule daily for ages 2 to 8; one to two for ages 9 to 16
- Adult serving: one to two capsules daily
- Pack size: 30 capsules / 15 to 30 adult servings
- Price per capsule: 68p
Viridian is one of the few L-theanine products with directions for children aged two and over. We liked that each capsule can be swallowed or opened and sprinkled into food or drink, which may help children who struggle with tablets.
The nutrition table lists 200mg L-theanine and 300mg lemon balm per two capsules, while the description suggests those amounts are in one capsule. At 68p per capsule, it is relatively expensive, but age-specific guidance, vegan formulation and strong BRC quality credentials make it the clearest child-focused option tested.
Available from:
Viridian (£20.35 / 30 capsules)
Serenova Focus with Creatine and Vitamin B12
Available from Serenova (£38)
Best L-theanine supplement with B12
Star rating: 4/5
- Format: powder sachets
- L-theanine per serving: 200mg
- Creatine monohydrate per serving: approximately 3g
- Other key ingredients: Korean ginseng, rhodiola, magnesium, iron, folic acid, vitamin B12 and vitamin E
- Daily serving: one 10g sachet mixed into juice, a shake or smoothie
- Pack size: 30 sachets / 30 servings
- Price per serving: £1.27, or £1.14 with subscription
Serenova takes a broader approach than a standalone L-theanine capsule. Each sachet provides 200mg L-theanine with around 3g creatine, Korean ginseng, rhodiola, magnesium, iron, folic acid, vitamin E and vitamin B12, creating a caffeine-free blend designed for daytime focus rather than bedtime use.
We liked the pre-measured format, which is easy to keep in a work bag and mix into juice, a smoothie or shake, and there was no distinct flavour. One sachet covers the daily serving, while the absence of caffeine makes it less likely to feel like a stimulant-led focus product.
At £1.27 per day, it is expensive beside simple L-theanine capsules, although the wider formulation explains some of the premium. The 200mg dose, creatine and sachets make this a daytime blend a good option for demanding days.
Available from:
Serenova (£38 / 30 sachets)
What does L-theanine do?
The amino acid L-theanine, found in green tea, appears to have a relaxing effect, thanks to its ability to increase alpha brain waves and as such it may help improve mood, relieve stress and maintain normal sleep. It is also associated with maintaining better attention and focus and regular consumption may, although more research is needed, be associated with less cognitive dysfunction, potentially also improving attention deficit hyperactivity disorder, according to research.
When is the best time to take L-theanine?
This depends on your health goal, it’s also worth bearing in mind that L-theanine is absorbed 30-60 minutes after consumption and remains active in the body for about five hours. So, if you want to improve focus, take L-theanine in the morning; for stress relief, take it in the afternoon or in the lead-up to a stressful event; and if it is to aid sleep, take L-theanine in the evening.
How should you take L-theanine for best absorption?
Take L-theanine on an empty stomach with a glass of water. It is best to take L-theanine away from other foods, especially a protein-rich meal that contains other amino acids. This is because protein foods will slow the uptake of L-theanine because other amino acids compete for absorption across the intestinal wall, according to research.
Can L-theanine interact with medicines or other supplements?
Yes, it can. If you’re taking medication to manage blood pressure, you should be aware that L-theanine may further lower your blood pressure. When taken alongside sedatives, it may increase drowsiness, and it may counteract the effects of stimulant drugs.
Always consult your GP or healthcare practitioner if you’re prescribed medication to ensure L-theanine is appropriate for you. Those who are pregnant or breastfeeding should exercise caution, as there is limited research available for these groups.
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Always keep supplements out of the reach of children. Unless otherwise stated, we tested products available in the UK market that are suitable for adults. Check the product label, ingredients and patient information leaflet before purchase to ensure the product is appropriate for your individual circumstances.
A qualified nutritionist (MBANT), Kerry Torrens is a contributing author to a number of nutritional and cookery publications, including Good Food. Kerry is a member of the Royal Society of Medicine, the Complementary and Natural Healthcare Council and the British Association for Applied Nutrition and Nutritional Therapy.
All health content is provided for general information only and should not be treated as a substitute for the medical advice of your own doctor or any other healthcare professional. If you have concerns about your health, contact your GP, pharmacist or another qualified healthcare professional. See our website’s terms and conditions for more information.