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High Strength L-Theanine Capsules - 400mg

UK's strongest L-Theanine - Pure & potent double-strength capsules

96 reviews9410020
Only 16.6p per capsule
In stock
- Best Price
Only 15.0p per capsule
0 in stock
In Stock

Key features

  • Aids relaxation
  • May improve quality of sleep
  • Popular alongside 5HTP
  • Strongest & purest form available
High Strength L-Theanine 400mg capsule view
Capsule Size
23mm x 8mm Oblong capsule
  • Description
  • Product Information
  • Feefo Reviews Reviews

Introducing our new double-strength L-Theanine capsules. L-Theanine supports a sense of calm, contentment and well-being. It crosses the blood brain barrier and has been shown to increase brain alpha waves in less than 40 minutes. Alpha brain waves are an indication of a state of relaxation and mental alertness similar to that achieved through meditation, this promotes a feeling of relaxation but with an alert state of mind. This is particularly useful to know as it can be taken during the day to support relaxation without a sedating effect.

Theanine is an amino acid found predominantly in tea.  When you have a stressful moment or a shock the immediate thought (well for us Brits anyway) is to have a 'cuppa'! A joke to some maybe, but is there a real reason as to why? Yes, it's L-Theanine, which is believed to be responsible for the calming and relaxing effect brought about by a good old cup of tea.

L-theanine facilitates the production of GABA (a neurotransmitter that has a calming effect on the brain), it has also been shown to support quality sleep and may have a positive effect on memory and learning. 

Purest form available, strong and high grade material

A single capsule provides 400mg of this high-grade amino acid in a vegetarian capsule - currently the strongest form available in the UK.

Nutritional Information
Each capsule typically provides:
L-Theanine 400mg
Allergen Advice
Any allergens are highlighted in bold in the ingredients list.
List of Ingredients
L-Theanine, Hydroxypropyl Methylcellulose, Stoneground Rice Flour, Rice Hulls, Rice Extract (with Rice Hulls, Gum Arabic, Sunflower Oil)
Dosage / Suggested Intake
Swallow one capsule per day with food, or as directed by your health professional.
Legal Category
Food Supplement


Customer Reviews for High Strength L-Theanine 400mg

The views expressed below are the personal opinion of Just Vitamins customers. Just Vitamins does not endorse these views, nor should they be regarded as health claims or medical advice. All reviews are collected and verified as genuine by a 3rd party called Feefo.

Overall product rating 9.4 / 10 - 96 customers have independently reviewed and recommend High Strength L-Theanine from 96 reviews (showing latest 50 reviews)
Review Date
Review Details
Service rating: Very prompt and efficient service
Product: Helps me to relax and get better sleep
Service rating: Ordered as previously happy with product and price. Now there is a much wider range available elsewhere with higher strength products available at lower cost.
Product: L theanine - taken for concentration and calm seems to have some benefits.
Service rating: They deliver things very quickly and in good packaging.
Product: These are good, they calm my moods right down. Strongly recommended for Fybro sufferers.
Fast efficient service as ever.
Service rating: As always super . From enquiry to delivery. Faultless.
Product: Smooth and calming product.
Service rating: Good products and great service.
Product: Find them very helpful and calming
Service rating: Fast delivery
Product: Amazed by their effectiveness. Very pleased, will buy again.
Service rating: Came very quickly
Product: Have been taking them for years
Service rating: Brilliant site
Product: Great for anxiety take before bed or in morning
Service rating: I think they are an honest firm with reasonable prices and I like the way they do not send their products in glass or plastic containers.
Product: It certainly seems to work for me.
Service rating: Fast delivery and high quality product. Loving how much it's enhanced my life already!
Product: I began taking L-Theanine after researching its positive effects on creativity and I can certainly say that this product does the job. Helps me stay focused, whilst calm at the same time.
Service rating: Speedy delivery ,good communication .
Product: It helps with my anxiety and my sleep
Service rating: Good customer service (originally was sent wrong item but they redelivered and sent A package to return the vitamins sent in error) however I’ve taken the same vitamins in pill form from 2 other brands and found them much more effective even though these are described as double the strength. Feel like these vitamins (l-theanine 400mg) just don’t really work.
Product: I have tried l-theanine from other brands taking pills half of the strength of these and they were far more effective. I didn’t feel like these worked at all unfortunately and would not purchase again.
Service rating: Prompt delivery, quality product, easy life
Product: Great product. This what I was looking for.
Service rating: Bought from them for quite a while, and will carry on doing.
Product: Tastes good. I use it with coffee mainly. It comes from green tea.
Service rating: Great choice of products, great quality, rapid service and always reliable.
Product: Great quality, the dosages is just right, quality is good and they are well sourced.
Great service
Brilliant product
The sale and delivery went through smoothly with no problems. I would use this company again.
Service rating: Excellent prompt service, love the pouch the tablets come in, keeps them fresh. Very happy with purchase.
Product: Im really impressed, will definitely be buying more. Overall benefits are very good.
Service rating: Very fast service and good prices of supplements! Would highly recommend!
Product: High potency and works very well to calm down and relax me.
Excellent service
Service rating: Just Vitamins is my go to vendor for majority of my supplement needs.
They have the best quality, constantly innovate on packaging and product constitution, and are extremely competitive on price.
I have been very satisfied with their L-Theanine as it provides the relaxation I sorely need in a high stress environment.
I do not hesitate in recommending Just Vitamins to anyone considering purchasing from them.
Product: This is a product I use regularly to destress and to help me sleep. The quality is good compared to rivals and the pricing is just right.
Service rating: Excellent and fast service
Product: I’m very pleased with the supplements which I bought , my health has improved significantly
Service rating: Excellent service, fast delivery. Very pleased.
Product: Definitely feel the positive effects of the supplement. This is a repeat order so that says it all.
Service rating: Item received very quick and kept informed of progress.
Product: Wanted to calm nerves as important speech and helped a lot.
Service rating: Ordering was simple and easy and they arrived earlier than expected and cost less than previous suppliers.
Product: Did what it said on the label and arrived in an easy to store resealable bag.
Service rating: Good selection. Decent choices of sizes and strengths. Price is a negative though.
Product: Works! Felt a big difference within a half hour and has continued working every day since!
Service rating: Fast, efficient, I can't fault them. Would highly recommend.
Product: they are cheap and reliable, if this is the supplement you need, these are fine.
Service rating: Arrived quickly and well packaged. Would definitely order from here again
Product: Definitely helps keep the jittery aspects of the caffeine buzz away. If you're caffeine sensitive like me, this helps keep you level and avoid the shakiness that can come with caffeine
Quick delivery and great product.
Service rating: First class service 9
Product: Good quality products at a good price
Service rating: Quick delivery and easy to use website. Product is good and I like their easy packaging so it fits in the letter box
Product: Seems to be working would buy again
The tablets came very quickly and the discount was very good.
Service rating: Fast delivery. Great quality of vitamins, will order again.
Product: Good quality product. Will order again.
Bra priser o snabb leverans
Service rating: Supurb! Just Vitamins do everything well. One of my favourite health supplement companies.
Product: One of the best relaxation products on the market.
Excellent. Would use again. .
Service rating: Prompt delivery. Great product. Competitive price.
Product: Helps me relax. Relives tension.
Service rating: Prompt delivery as always. I’m very pleased to see 400mg L Theanine back in stock. I had to buy from a different company last time as only 200mg were available. I don’t want to have to take two capsules when I can take one so it’s good to be back with Just Vitamins!
Product: Just Vitamins products always arrive quickly. Their use of sealed bags instead of plastic tubs means multiple orders can be delivered in an A4 padded envelope together. Also the packaging does not cantain plastic. Great service.
Service rating: Prompt delivery
Product: Not sure if it is helping yet as I haven’t taken it for long enough
Great as always
Quick delivery and quality products. Trusted them for years and never had a problem.
Service rating: Very prompt service, would definitely recommend
Product: Very effective, works quickly for me.
There was a glitch in my order and they fixed it, no quibbles.
shipped quickly without hassle the items i purchased.
Brilliant. Helped me sleep. Warm fuzzy feeling is both relaxing and enjoyable.

A must have !
Service rating: The site works as it should do with a dedicated page for re-ordering items you've bought before.
They could improve this re-order page by allowing you to delete items that you have had problems with and have no intention of buying again, especially when they have refunded the cost of the item(s) complained about.
Product: I find they have the calming effect claimed for this product.
Service rating: Quickly dispatched and delivered only negative is the tablets don’t work for me
Product: No side effects but no good effects either. I take these to help with anxiety induced tremors.
Feedback Response: Hi, sorry to hear that you did not find this supplement to be effective for you. Perhaps you might get better results with 5-HTP?
Let us know how you get on.
Ian - Just Vitamins Customer Team
Service rating: Fast delivery, great prices.
Product: L-theanine is subtle but very effective. I have found that it's great for a) a calm focus, b) reducing stress and c) helping you achieve a deep long sleep without any drowsiness in the morning.
Service rating: Quick delivery good website cheap prices.
Product: Why three stars because the vitamens placed in plastic bag instead of can or box so when i picked it from my mail box it was very warm.

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