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Dietary supplement

Theanine 100 mg Ingredients & Drug Interactions

by Higher Nature

Theanine 100 mg label
See full label image
Capsule Category: Amino Acid/protein
Most serious interaction: Moderate
Clinical methodology reviewed by · Updated Sep 30, 2026 · Label data from the NIH DSLD
What is this page for?

First and foremost: checking Theanine 100 mg against your medications. The heart of this page is the interaction checker and the full interaction report — how this product’s ingredients may interact with prescription and over-the-counter medicines you may be taking.

Around that, we add a pharmacist’s high-level view of the product as a whole — what’s inside, the evidence for its stated use, how transparent the label is, and what safety data exists — so you can see the full picture in one place. It’s educational information from our licensed clinical databases and the clinical staff at HelloPharmacist — not medical advice — and we don’t sell or endorse products. Our editorial policy

The interaction bottom line Most serious interaction: Moderate

Theanine 100 mg is a dietary supplement by Higher Nature with 1 active ingredient. Its ingredients are commonly taken for anxiety and stress, relaxation and calm, sleep support.Based on those ingredients, 565 medications have a known interaction with it, the most serious rated moderate. The ingredients most likely to interact are Theanine. Use the checker below to test your specific medication, or read the full HelloPharmacist Interaction Report.

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Check Your Meds Against Theanine 100 mg by Higher Nature

Ask about any prescription or over-the-counter medication and we check it for interactions with Theanine 100 mg by Higher Nature — and tell you which ingredient is responsible.

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HelloPharmacist Scorecard of Theanine 100 mg by Higher Nature

Our pharmacy team’s full take, with four database checks built into the cards below — a summary of what is known, not a grade of the product itself.

From our pharmacy team — supplement deep dive

Generated from HelloPharmacist’s pharmacist-curated databases and editorial rules · Last generated Jul 11, 2026

What’s inside

Full disclosure
Ingredient Transparency · database check
Full

Every active ingredient lists its own amount on the label.

Why this rating?
  • The label discloses an exact amount for 1 of its 1 active ingredient.
  • No proprietary blends here — you can verify the dose of every single component.

This product contains a single active ingredient: theanine, an amino acid naturally found in tea. Theanine is included in a capsule made from hydroxypropyl methylcellulose, cellulose, silicon dioxide, and magnesium stearate.

Does it work?

Moderate evidence
Evidence for Intended Use · database check
By FDA rules, dietary supplements can’t claim to treat, cure, or prevent disease — so labels speak in careful marketing language. We discern each product’s intended use from its name, label claims, and label statements, then grade the clinical evidence for that use. How these ratings are computed

This product doesn't appear to be marketed for a specific use, so we graded Theanine's overall clinical evidence instead.

Moderate

Some clinical evidence supports Theanine for:

Why this rating?
  • We looked at the product name, claims, and label statements and couldn't find a stated purpose to grade.
  • Since the label doesn't commit to one use, we graded the ingredient's overall clinical evidence instead.
  • On file: Cognitive function — rated "Possibly Effective" (Natural Medicines).

The evidence for theanine is mixed. It's rated possibly effective for cognitive function—meaning there's some support for it, but the data isn't rock-solid yet.

For age-related cognitive decline, Alzheimer disease, generalized anxiety, OCD, and cancer, the evidence we have is insufficient to rate it one way or the other. If you're thinking about it for one of those conditions, that's a conversation to have with your doctor or pharmacist about what the current science actually shows.

The evidence, ingredient by ingredient Theanine

How safe is it?

Well-documented data
Safety Information · database check
Well characterized

Adverse-effect, pregnancy, and general safety data are on file for most of these ingredients.

Why this rating?
  • We hold adverse-effect (side-effect) data for 1 of the 1 matched ingredient.
  • Pregnancy & breastfeeding safety ratings cover 1 of 1.
  • General safety write-ups exist for 1 of 1.
  • Remember: this measures how much safety information exists. Thin data is not the same as being safe.

Theanine is generally well tolerated in healthy adults for short-term use, but we don't know much about what happens if you take it long-term. The most common side effects reported are headaches, drowsiness, longer sleep, and more vivid dreams.

One case of a facial tic was reported in a child taking 400 mg daily, but the tic stopped when the child quit the supplement—and since the child had a history of tics, it wasn't clear the supplement was to blame. If you're pregnant or breastfeeding, there isn't enough safety data to know either way, so talk with your doctor or pharmacist before using it.

Side effects, ingredient by ingredient Theanine

Meds to double-check

Moderate interaction found
Known Interaction Concern · database check
Moderate identified

The most serious documented interaction for these ingredients is Moderate. Check your medications for a personalized result.

Why this rating?
  • 1 of the 1 matched ingredient can interact with medications — Theanine.
  • The most serious interaction on file is rated Moderate.
  • For scale: 565 individual medications appear in the full list. A big number alone doesn't make a product dangerous — what matters is whether YOUR medication is on it, so run yours through the interaction checker on this page.

Double-check this product if you take blood pressure medication (the most important one), any kind of sleep aid or sedating medication, or an antidepressant or other serotonergic drug. Use the search tool on this page to verify your exact medications before starting.

Check your own medication Run your meds through the checker above

The bottom line

Scorecard at a glanceFully disclosed formula with some supporting evidence behind its ingredients' uses. Moderate medication interactions have been identified, and safety information is well characterized.

Theanine might help with focus and mental clarity, though the evidence is still developing. If you take blood pressure medication, a sleep aid, an anti-anxiety drug, or an antidepressant, check with us first—it could amplify or interact with those effects.

For short-term use in healthy adults, it's generally well tolerated.

Educational only — not medical advice; always confirm with your pharmacist. Our editorial policy · How we use AI

Assessment coverage: 1 of 1 active ingredient matched to our full ingredient reviews (monographs). Based on the product label dated Dec 29, 2014.

This Scorecard evaluates available label information, ingredient evidence, and known medication-safety considerations. It does not independently verify product identity, purity, potency, contamination, or manufacturing quality. How these ratings are computed

At a glance

General information

Key facts about Theanine 100 mg, straight from the product label.

Brand Higher Nature
Barcode (UPC) 5031013105074
Net contents 60 Capsule(s)
Market status On market
Date entered into DSLD Dec 29, 2014
DSLD ID 40863
Product type Amino Acid/protein
Supplement form Capsule
Dietary claims / uses All Other
Intended target group(s) Children 4 or More Years of Age, Vegan, Vegetarian, Adult (18 - 50 Years), No Allergies, Gluten Free
From the label
Everything in this section is reproduced from the manufacturer’s own product label — it’s the label speaking, not HelloPharmacist. We show it so you can see exactly what the maker states; we don’t verify or endorse those statements.

Supplement Facts

The label details for Theanine 100 mg by Higher Nature, sourced from the NIH Dietary Supplement Label Database.

Supplement Facts

Daily Value (DV) Target Group(s):
Adults and children 4 or more years of age
Minimum serving Sizes:
1 Capsule(s)
Maximum serving Sizes:
2 Capsule(s)
UPC/BARCODE
5031013105074
IngredientAmount% DV
Theanine100 mg--

Other ingredients: L-Theanine, Hydroxypropyl Methylcellulose, Cellulose, Silicon Dioxide, Magnesium Stearate

Tap any ingredient to jump to its full detail below.

Label statements
These statements are the manufacturer’s wording, reproduced from the product label — the label is saying it, not HelloPharmacist. We don’t verify or endorse them.
General Statements

This bottle has a UV filter.

Hypo-allergenic formula.

This product is not tested on animals.

Charitable organisations policy: supplements regularly donated

PREMIUM NATURALS

Food supplements should not be used as a substitute for a varied and balanced diet and healthy lifestyle.

Theanine is an amino acid found in green tea.

Precautions

Keep out of reach of children.

Do not exceed recommended daily intake.

Storage

Ensure lid is tight and store in a cool, dry, steam-free environment as damp conditions can affect the product quality.

General

QTH060 105 QTH-286-02

Formulation

DOES NOT CONTAIN: sugar, salt, starch, soya, wheat, gluten, maize, corn, yeast, lactose, dairy products, artificial preservatives, colours or flavourings.

Suitable for vegetarians and vegans.

VEGETARIAN

Seals/Symbols

Lid {Recycle} 5 PP

Jar {Recycle} 1 PET

FDA Statement of Identity

FOOD SUPPLEMENT

Suggested/Recommended/Usage/Directions

DIRECTIONS: Take 1-2 capsules a day (children over 8 years, 1 capsule a day), between meals, or as your health professional advises.

Is this label outdated? Report a formula or label change and our pharmacy team will review it.

See for yourself

Theanine 100 mg by Higher Nature label

The label scan from the NIH Dietary Supplement Label Database. Tap to enlarge.

Theanine 100 mg label

Label images are published by the NIH Dietary Supplement Label Database for the version of this product on file. Always read your actual product label.

View the full label (PDF)
What’s inside

The Ingredients in Theanine 100 mg by Higher Nature

This is the 1 active ingredient this product is made of. Select it to open its full monograph.

Serving size1 Capsule(s) Dosage formCapsule Amounts shown are per serving.

Theanine

Interacts with
565 drugs
100 mg per serving

Theanine (usually L-theanine) is an amino acid found naturally in tea leaves that many people take to feel calmer and less stressed without strong dro...

Theanine monograph & interactions

Other (inactive) ingredients: L-Theanine, Hydroxypropyl Methylcellulose, Cellulose, Silicon Dioxide, Magnesium Stearate. These complete the product’s ingredient list but are not active constituents.

Interaction report

Theanine 100 mg by Higher Nature Drug Interactions

Want to check YOUR meds against Theanine 100 mg?

Ask about interactions with your drugs in plain English — “Can I take it with lisinopril?” — and we find you the answer in seconds, ingredient by ingredient.

 Go to the checker
565Drugs
172 Moderate 393 Minor

Ingredients driving the most interactions

Theanine 565

Individual Drug Interactions

The ingredients in Theanine 100 mg interact with 565 drugs. Click any drug to see the details.

1 of the 1 ingredient in Theanine 100 mg interact with drugs. Each result below shows which ingredient is responsible. Theanine

Each ingredient & the kinds of drugs it affects

For each ingredient in Theanine 100 mg with known interactions, here are the types of medications it can affect. Open any type for the detail — or search your exact drug in the checker above.

Theanine3 drug types · 565 drugs

Antihypertensive Drugs

Theanine might lower blood pressure, potentiating the effects of antihypertensive drugs.
Animal research shows that theanine can lower blood pressure in spontaneously hypertensive animals. Theoretically, concomitant use of theanine and antihypertensive drugs might potentiate the antihypertensive activity.

Likelihood Possible Evidence D
Cns Depressants

Theoretically, theanine might have additive sedative effects when used in conjunction with CNS depressants. However, it is unclear if this concern is clinically relevant.
Theoretically, theanine may compete with glutamate and/or increase plasma gamma-aminobutyric acid (GABA) levels, which could cause CNS depression. In one clinical study, some subjects taking oral theanine reported drowsiness.

Likelihood Unlikely Evidence D
Serotonergic Drugs

Clinical studies regarding the effects of L-theanine on serotonin levels are conflicting. Some studies suggest it can increase serotonin levels in the brain while others report that it may decrease them. Nevertheless, there have been no reports of l-theanine being a causative agent in serotonergic-related side effects or serotonin syndrome.

Likelihood Unlikely Evidence C
Theanine full monograph & interactions
The maker

Brand information

Manufacturer and brand details for Theanine 100 mg, from the product label.

Higher Nature

See all Higher Nature products
Name
Higher Nature
City
Burwash Common
State
East Sussex
ZipCode
TN19 7LX
Web Address
www.highernature.com
Pharmacist Counseling Corner

Theanine 100 mg by Higher Nature: Common Questions

Does Theanine 100 mg by Higher Nature interact with any medications?
Yes. Based on its ingredients, Theanine 100 mg has a known interaction with 565 medications. Use the checker to see how it interacts with a specific drug.
How can one product interact with so many drugs?
Theanine 100 mg contains a single active ingredient, and that one ingredient can interact with many different medications on its own. We check it against each medication and show the mechanism responsible.
Where does this information come from?
The product label data comes from the NIH Dietary Supplement Label Database (DSLD); the interaction data is built on the Natural Medicines database and reviewed by HelloPharmacist pharmacists.
What is theanine and what does it do?
Theanine is an amino acid found naturally in tea. It's possibly effective for supporting cognitive function, though the evidence is still being studied. It may also influence brain chemistry in ways that could affect mood and alertness, which is why interactions with certain medications are a concern.
Can I take this if I'm on blood pressure medicine?
Not without checking first. Theanine may lower blood pressure itself, so combining it with blood pressure medication could lower your pressure too much. Talk to your pharmacist or doctor—they can help you decide if it's safe for you or if you need to adjust anything.
What side effects should I watch for?
The most common ones are headaches, drowsiness, longer sleep, and more vivid dreams. These are usually mild, but if you notice anything that concerns you, stop taking it and let your pharmacist know.
Is it safe to take while pregnant or breastfeeding?
There isn't enough safety data to know either way. It's best to avoid it during pregnancy and breastfeeding and talk with your doctor or pharmacist for personalized advice based on your situation.
How long does it take to work?
The facts we have don't tell us how quickly you'd notice an effect. That's a good question for your pharmacist, who can explain what the research shows about timing.

Written and reviewed by the HelloPharmacist editorial staff. Our editorial policy

Not sure if Theanine 100 mg is safe with your meds?

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Label information is sourced from the NIH Dietary Supplement Label Database and reflects the product version on file; always read your actual product label. This page is for education only and is not a substitute for professional medical advice. Confirm with your pharmacist or doctor before combining supplements and medications.

Theanine 100 mg label
Go deeper

The Full Monographs Behind Theanine 100 mg’s Ingredients

Every ingredient we hold a full HelloPharmacist monograph for — uses, evidence, safety, and the complete interaction list.

Herb & supplement monograph

Theanine

Interacts with 565 drugs

Theanine (usually L-theanine) is an amino acid found naturally in tea leaves that many people take to feel calmer and less stressed without strong drowsiness. Early research suggests it may...

Read the full Theanine monograph →
Sources

Sources & How We Checked

Theanine 100 mg's label data comes from the NIH Dietary Supplement Label Database; the ingredient interaction data is from the Natural Medicines database, reviewed by our pharmacists.

Content is written and reviewed by licensed HelloPharmacist pharmacists. See our data sources and editorial standards for how this information is built and checked.

The 6 references behind this product’s interaction data

Every citation that drives the interaction findings for this product’s ingredients, from the evidence-graded Natural Medicines (TRC Healthcare) database. Open an ingredient to browse its citations — links open the study on PubMed or the publisher’s site.

Theanine 6 references
  1. Yokogoshi H, Kobayashi M. Hypotensive effect of gamma-glutamylethylamide in spontaneously hypertensive rats. Life Sci 1998;62:1065-8.
  2. Haskell, C. F., Kennedy, D. O., Milne, A. L., Wesnes, K. A., and Scholey, A. B. The effects of L-theanine, caffeine and their combination on cognition and mood. Biol.Psychol. 2008;77(2):113-122. PubMed
  3. Yokogoshi, H., Kato, Y., Sagesaka, Y. M., Takihara-Matsuura, T., Kakuda, T., and Takeuchi, N. Reduction effect of theanine on blood pressure and brain 5-hydroxyindoles in spontaneously hypertensive rats. Biosci.Biotechnol.Biochem. 1995;59(4):615-618. PubMed
  4. Lyon MR, Kapoor MP, Juneja LR. The effects of L-theanine (Suntheanine®) on objective sleep quality in boys with attention deficit hyperactivity disorder (ADHD): a randomized, double-blind, placebo-controlled clinical trial. Altern Med Rev. 2011;16(4):348-
  5. Hidese S, Ota M, Wakabayashi C, et al. Effects of chronic l-theanine administration in patients with major depressive disorder: an open-label study. Acta Neuropsychiatr 2017;29(2):72-9.
  6. Tsuchiya T, Honda H, Oikawa M, et al. Oral administration of the amino acids cystine and theanine attenuates the adverse events of S-1 adjuvant chemotherapy in gastrointestinal cancer patients. Int J Clin Oncol 2016;21(6):1085-90. PubMed

See these in context on the Theanine monograph →

Parts of this content are provided by the Therapeutic Research Center, LLC.

DISCLAIMER: Currently this does not check for drug-drug interactions. This is not an all-inclusive comprehensive list of potential interactions and is for informational purposes only. Not all interactions are known or well-reported in the scientific literature, and new interactions are continually being reported. Input is needed from a qualified healthcare provider including a pharmacist before starting any therapy. Application of clinical judgment is necessary.

© 2021 Therapeutic Research Center, LLC

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