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Dietary supplement

Double Strength L-Theanine 200 mg Ingredients & Drug Interactions

by NOW

Double Strength L-Theanine 200 mg label
See full label image
Capsule Category: Other Combinations
Most serious interaction: Moderate
Clinical methodology reviewed by · Updated Sep 16, 2026 · Label data from the NIH DSLD
What is this page for?

First and foremost: checking Double Strength L-Theanine 200 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

Double Strength L-Theanine 200 mg is a dietary supplement by NOW with 2 active ingredients. Its ingredients are commonly taken for polycystic ovary syndrome (pcos), anxiety and panic, depression and mood.Based on those ingredients, 651 medications have a known interaction with it, the most serious rated moderate. The ingredients most likely to interact are L-Theanine, Inositol. Use the checker below to test your specific medication, or read the full HelloPharmacist Interaction Report.

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Check Your Meds Against Double Strength L-Theanine 200 mg by NOW

Ask about any prescription or over-the-counter medication and we check it for interactions with Double Strength L-Theanine 200 mg by NOW — and tell you which ingredient is responsible.

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HelloPharmacist Scorecard of Double Strength L-Theanine 200 mg by NOW

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 2 of its 2 active ingredients.
  • No proprietary blends here — you can verify the dose of every single component.

This product contains two active ingredients. Inositol is a naturally occurring compound that plays a role in cell signaling and has been studied in conditions like polycystic ovary syndrome (PCOS) and metabolic syndrome.

L-Theanine is an amino acid found in green tea that's been studied for cognitive function and relaxation. The capsule also contains inactive ingredients (hypromellose, stearic acid, and silicon dioxide) as binders and flow agents.

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
Moderate

Some clinical evidence supports this product's ingredients for its stated purpose, but it isn't conclusive.

Why this rating?
  • The label markets this product for: relaxation and cognitive function with stress management.
  • We looked for evidence on: Anxiety, Generalized anxiety disorder (GAD), Panic disorder, Stress, Insomnia, Cognitive function — and 4 related terms.
  • The strongest evidence on file: Theanine is rated "Possibly Effective" for Cognitive function (Natural Medicines).
  • Also on file: Inositol is rated "Possibly Ineffective" for Acute respiratory distress syndrome (ARDS), Anxiety.
  • Also on file: Inositol is rated "Insufficient Reliable Evidence To Rate" for Insomnia, Panic disorder, Post-traumatic stress disorder (PTSD).

Inositol is possibly effective for PCOS, metabolic syndrome, and preterm labor, but the evidence for anxiety, diabetic neuropathy (nerve damage from high blood sugar), and depression rates as possibly ineffective. L-Theanine is possibly effective for cognitive function, but evidence is insufficient to rate its effects on age-related cognitive decline, Alzheimer disease, generalized anxiety disorder (GAD), obsessive-compulsive disorder (OCD), or cancer.

If you're considering this product for a specific condition, talk with your pharmacist about what the current evidence actually shows for your situation.

The evidence, ingredient by ingredient Inositol 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 2 of the 2 matched ingredients.
  • Pregnancy & breastfeeding safety ratings cover 2 of 2.
  • General safety write-ups exist for 2 of 2.
  • Remember: this measures how much safety information exists. Thin data is not the same as being safe.

Both ingredients are generally well tolerated at standard doses. Inositol's most common side effects are diarrhea, gas, and nausea.

L-Theanine may cause headaches, drowsiness, or vivid dreams in some people. There's not enough safety data on either ingredient during pregnancy or breastfeeding, so the safety data advises against use in those times — talk with your doctor or pharmacist if you're pregnant, planning pregnancy, or nursing before taking this product.

Side effects, ingredient by ingredient Inositol 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?
  • 2 of the 2 matched ingredients can interact with medications — Inositol, Theanine.
  • The most serious interaction on file is rated Moderate.
  • Some involve high-stakes drug classes: diabetes medications.
  • For scale: 651 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.

Check your antidiabetes drugs (insulin, metformin, sulfonylureas) and antihypertensive drugs (blood pressure medications) with your pharmacist before starting — inositol may increase low blood sugar risk and L-Theanine may lower blood pressure further. If you take sedatives or sleep aids, or serotonergic antidepressants, mention those too, though the Minor interaction risk is theoretical.

Check your own medication Run your meds through the checker above

The bottom line

Scorecard at a glanceFully disclosed formula with some supporting evidence for its stated purpose. Moderate medication interactions have been identified, and safety information is well characterized.

This product may be worth considering if you're interested in inositol for PCOS or metabolic issues, or L-Theanine for general cognitive support. If you take antidiabetes drugs, antihypertensive drugs, sedatives, or certain antidepressants, check your medications with your pharmacist first.

Long-term safety data on L-Theanine is limited, so talk with your pharmacist about how long you plan to use it.

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

Assessment coverage: 2 of 2 active ingredients matched to our full ingredient reviews (monographs). Based on the product label dated Jul 25, 2024.

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 Double Strength L-Theanine 200 mg, straight from the product label.

Brand NOW
Barcode (UPC) 733739001481
Net contents 120 Veg Capsule(s)
Market status On market
Date entered into DSLD Jul 25, 2024
DSLD ID 314284
Product type Other Combinations
Supplement form Capsule
Dietary claims / uses Nutrient, All Other, Structure/Function
Intended target group(s) Vegan, Vegetarian, Adult (18 - 50 Years), Kosher, Gluten Free, Dairy 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 Double Strength L-Theanine 200 mg by NOW, 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 Veg Capsule(s)
Maximum serving Sizes:
1 Veg Capsule(s)
Servings per container
120
UPC/BARCODE
733739001481
IngredientAmount% DV
Inositol100 mg--
L-Theanine200 mg--

Other ingredients: Hypromellose, Stearic Acid, Silicon Dioxide

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.
Suggested/Recommended/Usage/Directions

Suggested Usage: Take 1 capsule 1 to 2 times daily as needed, preferably on an empty stomach.

Formula

L-Theanine is a unique amino acid found naturally found in the tea plant (Camellia sinensis). L-Theanine promotes relaxation while maintaining alertness and promotes healthy cognitive function. L-Theanine may also support healthy vascular function through this relaxing effect.

Double Strength L-Theanine 200 mg with Inositol

Triangle K (Kosher)

This product has twice the L-Theanine (200 mg per capsule) as in our regular strength product (100 mg per capsule).

FDA Disclaimer Statement

These statements have not been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure or prevent any disease.

Precautions

Caution: For adults only. Keep out of reach of children.

Consult physician if pregnant/nursing, taking medication, or have a medical condition.

Not manufactured with wheat, gluten, soy, milk, egg, fish, shellfish or tree nut ingredients. Produced in a GMP facility that processes other ingredients containing these allergens.

Formulation

Natural color variation may occur in this product.

Stress Management Promotes Relaxation Healthy Vascular Function

Non-GMO

Vegetarian/Vegan

Not manufactured with wheat, gluten, soy, milk, egg, fish, shellfish or tree nut ingredients.

FDA Statement of Identity

A Dietary Supplement

Seals/Symbols

Triangle K (Kosher)

GMP Quality Assured

General Statements

Amino Acids Family owned since 1968.

Storage

Store in a cool, dry place after opening.

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

See for yourself

Double Strength L-Theanine 200 mg by NOW label

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

Double Strength L-Theanine 200 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 Double Strength L-Theanine 200 mg by NOW

These are the 2 active ingredients this product is made of. Select any to open its full monograph.

Serving size1 Veg Capsule(s) Dosage formCapsule Servings per container120 Amounts shown are per serving.

Most supplement products combine several ingredients, and a medication can interact with the product through any one of them. Each ingredient below shows whether it has known drug interactions.

Inositol

Interacts with
86 drugs
100 mg per serving

Inositol is a sugar alcohol made naturally in the body and found in many foods, and it is sold as a supplement (often myo-inositol) mainly for PCOS, m...

Inositol monograph & interactions

L-Theanine

Interacts with
565 drugs
200 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...

L-Theanine monograph & interactions

Other (inactive) ingredients: Hypromellose, Stearic Acid, Silicon Dioxide. These complete the product’s ingredient list but are not active constituents.

Interaction report

Double Strength L-Theanine 200 mg by NOW Drug Interactions

Want to check YOUR meds against Double Strength L-Theanine 200 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
651Drugs
258 Moderate 393 Minor

Ingredients driving the most interactions

L-Theanine 565
Inositol 86

Individual Drug Interactions

The ingredients in Double Strength L-Theanine 200 mg interact with 651 drugs. Click any drug to see the details.

2 of the 2 ingredients in Double Strength L-Theanine 200 mg interact with drugs. Each result below shows which ingredient is responsible. L-Theanine Inositol

Each ingredient & the kinds of drugs it affects

For each ingredient in Double Strength L-Theanine 200 mg with known interactions, here are the types of medications they can affect. Open any type for the detail — or search your exact drug in the checker above.

L-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
L-Theanine full monograph & interactions

Inositol1 drug type · 86 drugs

Antidiabetes Drugs

Theoretically, taking inositol with antidiabetes drugs might increase the risk of hypoglycemia.
Clinical research shows that inositol lowers blood glucose levels and glycated hemoglobin (HbA1c) levels in patients with diabetes.

Likelihood Possible Evidence A
Inositol full monograph & interactions
The maker

Brand information

Manufacturer and brand details for Double Strength L-Theanine 200 mg, from the product label.

NOW

See all NOW products
Name
NOW FOODS
Street Address
395 S. Glen Ellyn Rd.
City
Bloomingdale
State
IL
ZipCode
60108
Web Address
nowfoods.com
Pharmacist Counseling Corner

Double Strength L-Theanine 200 mg by NOW: Common Questions

Does Double Strength L-Theanine 200 mg by NOW interact with any medications?
Yes. Based on its ingredients, Double Strength L-Theanine 200 mg has a known interaction with 651 medications. Use the checker to see how it interacts with a specific drug.
How can one product interact with so many drugs?
Double Strength L-Theanine 200 mg contains 2 active ingredients, and an interaction can come from any of them. We check every ingredient, combine the results into one list per medication, and show which ingredient and mechanism is 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.
Does L-Theanine make you sleepy?
Some people report drowsiness, increased sleep duration, and more vivid dreams after taking L-Theanine, though this doesn't happen to everyone. If you're sensitive to it, start low and see how you feel.
Can I take this if I have diabetes and take medication for it?
Inositol in this product may lower blood sugar levels further, raising the risk of going too low. Talk with your doctor or pharmacist first — they can watch your blood sugar more closely if you decide to use it.
Is this safe during pregnancy?
There isn't enough reliable safety data for either ingredient during pregnancy. The safety data advises against use, so talk with your doctor or pharmacist before taking this if you're pregnant or planning to be.
Can I take this while breastfeeding?
There isn't enough safety data on L-Theanine or inositol while breastfeeding. The safety data advises against it, so check with your doctor or pharmacist before use if you're nursing.
What is inositol actually for?
Inositol has been studied most for polycystic ovary syndrome (PCOS) and metabolic syndrome — it's possibly effective for both. It's also been studied for preterm labor prevention. It hasn't panned out as well for anxiety or depression.
Will this really help my memory or focus?
L-Theanine is possibly effective for cognitive function, but evidence is insufficient on whether it helps with age-related memory loss or Alzheimer disease specifically. If that's your goal, ask your pharmacist whether the evidence is strong enough for your needs.

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

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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.

Double Strength L-Theanine 200 mg label
Go deeper

The Full Monographs Behind Double Strength L-Theanine 200 mg’s Ingredients

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

Herb & supplement monograph

Inositol

Interacts with 86 drugs

Inositol is a sugar alcohol made naturally in the body and found in many foods, and it is sold as a supplement (often myo-inositol) mainly for PCOS, mood, and metabolic concerns. The stronge...

Read the full Inositol monograph → 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

Double Strength L-Theanine 200 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 20 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.

Inositol 14 references
  1. Palatnik A, Frolov K, Fux M, Benjamin J. Double-blind, controlled, crossover trial of inositol versus fluvoxamine for the treatment of panic disorder. J Clin Psychopharmacol 2001;21:335-9.. PubMed
  2. Allan SJ, Kavanagh GM, Herd RM, Savin JA. The effect of inositol supplements on the psoriasis of patients taking lithium: a randomized, placebo-controlled trial. Br J Dermatol 2004;150:966-9. PubMed
  3. Machado-Vieira R, Viale CI, Kapczinski F. Mania associated with an energy drink: the possible role of caffeine, taurine, and inositol. Can J Psychiatry 2001;46:454-5. PubMed
  4. Kamenov Z, Kolarov G, Gateva A, Carlomagno G, Genazzani AD. Ovulation induction with myo-inositol alone and in combination with clomiphene citrate in polycystic ovarian syndrome patients with insulin resistance. Gynecol Endocrinol 2015;31(2):131-5. PubMed
  5. Matarrelli B, Vitacolonna E, D'Angelo M, et al. Effect of dietary myo-inositol supplementation in pregnancy on the incidence of maternal gestational diabetes mellitus and fetal outcomes: a randomized controlled trial. J Matern Fetal Neonatal Med 2013;26(1 PubMed
  6. Mukai T, Kishi T, Matsuda Y, Iwata N. A meta-analysis of inositol for depression and anxiety disorders. Hum Psychopharmacol 2014;29(1):55-63. PubMed
  7. Farren M, Daly N, McKeating A, Kinsley B, Turner MJ, Daly S. The Prevention of Gestational Diabetes Mellitus With Antenatal Oral Inositol Supplementation: A Randomized Controlled Trial. Diabetes Care. 2017;40(6):759-63. PubMed
  8. Zheng X, Liu Z, Zhang Y, et al. Relationship Between Myo-Inositol Supplementary and Gestational Diabetes Mellitus: A Meta-Analysis. Medicine (Baltimore). 2015;94(42):e1604. PubMed
  9. Crawford TJ, Crowther CA, Alsweiler J, Brown J. Antenatal dietary supplementation with myo-inositol in women during pregnancy for preventing gestational diabetes. Cochrane Database Syst Rev. 2015;(12):CD011507. PubMed
  10. Maurizi AR, Menduni M, Del Toro R, et al. A pilot study of D-chiro-inositol plus folic acid in overweight patients with type 1 diabetes. Acta Diabetol. 2017;54(4):361-65. PubMed
  11. Leppink EW, Redden SA, Grant JE. A double-blind, placebo-controlled study of inositol in trichotillomania. Int Clin Psychopharmacol. 2017;32(2):107-14. PubMed
  12. Lam S, Mandrekar SJ, Gesthalter Y. A Randomized Phase IIb Trial of myo-Inositol in Smokers with Bronchial Dysplasia. Cancer Prev Res (Phila). 2016;9(12):906-14.
  13. Wozniak J, Faraone SV, Chan J, et al. A randomized clinical trial of high eicosapentaenoic acid omega-3 fatty acids and inositol as monotherapy and in combination in the treatment of pediatric bipolar spectrum disorders: a pilot study. J Clin Psychiatry. PubMed
  14. Vitale SG, Corrado F, Caruso S, et al. Myo-inositol supplementation to prevent gestational diabetes in overweight non-obese women: bioelectrical impedance analysis, metabolic aspects, obstetric and neonatal outcomes - a randomized and open-label, placebo-

See these in context on the Inositol monograph →

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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