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Dietary supplement

L-Theanine Ingredients & Drug Interactions

by SmarterVitamins

Softgel Capsule Category: Other Combinations
Most serious interaction: Moderate
The interaction bottom line Most serious interaction: Moderate

L-Theanine is a dietary supplement by SmarterVitamins with 2 active ingredients. Its ingredients are commonly taken for source of omega-3 (ala) fatty acids, heart and cholesterol health, dry skin and inflammation.Based on those ingredients, 665 medications have a known interaction with it, the most serious rated moderate. The ingredients most likely to interact are L-Theanine, Flaxseed Oil. Use the checker below to test your specific medication, or read the full HelloPharmacist Interaction Report.

HelloPharmacist Scorecard of L-Theanine by SmarterVitamins

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

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.

SmarterVitamins L-Theanine is a 2-ingredient softgel with flaxseed oil and L-theanine as the active components. Flaxseed oil is a plant-based omega-3 source, and L-theanine is an amino acid found naturally in tea.

The capsule itself is made from softgel material, beeswax, and sunflower lecithin.

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: mental clarity, focus, alertness and calmness.
  • We looked for evidence on: Cognitive function, Attention deficit-hyperactivity disorder (ADHD), Generalized anxiety disorder (GAD), Stress, Insomnia, Concentration — and 2 related terms.
  • The strongest evidence on file: Theanine is rated "Possibly Effective" for Cognitive function (Natural Medicines).
  • Also on file: Flaxseed Oil is rated "Insufficient Reliable Evidence To Rate" for Attention deficit-hyperactivity disorder (ADHD), Cognitive function.
  • Also on file: Theanine is rated "Insufficient Reliable Evidence To Rate" for Anxiety, Attention deficit-hyperactivity disorder (ADHD), Generalized anxiety disorder (GAD), Insomnia.

The evidence for L-theanine on cognitive function is possibly effective based on the data we hold, though studies on age-related cognitive decline, Alzheimer disease, anxiety disorders, and cancer are insufficient to rate. Flaxseed oil shows possibly ineffective ratings for obesity, rheumatoid arthritis, bipolar disorder, and high cholesterol (hyperlipidemia) — meaning the evidence does not support its use for these purposes.

The evidence, ingredient by ingredient Flaxseed Oil 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.

L-theanine is generally well tolerated in healthy adults for short-term use, but long-term safety hasn't been well studied. The safety data advises against its use during pregnancy and breastfeeding because there isn't enough information to know it's safe.

Flaxseed oil is generally well tolerated, though a small number of people report changes in bowel habits, dry mouth, or upset stomach at typical doses; higher doses can cause loose stools or diarrhea. Rare severe allergic reactions are possible.

The safety data for flaxseed oil in pregnancy is rated possibly safe, but there's limited information during breastfeeding, so medical advice is recommended.

Side effects, ingredient by ingredient Flaxseed Oil 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 — Flaxseed Oil, Theanine.
  • The most serious interaction on file is rated Moderate.
  • Some involve high-stakes drug classes: anticoagulant / antiplatelet drugs.
  • For scale: 665 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.

Before taking this product, double-check with your doctor or pharmacist if you take blood thinners or antiplatelet drugs (moderate risk of increased bleeding), blood pressure medications (moderate risk of low blood pressure), ezetimibe/Zetia (blocks absorption of the flaxseed oil component), sedating drugs like sleep aids (minor risk of added drowsiness), or serotonergic medications like antidepressants (minor theoretical interaction, though no cases have been reported).

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 combines flaxseed oil and L-theanine, two ingredients with limited proven effectiveness for their common uses. The bigger question is whether it interacts with your blood pressure medication, blood thinners, cholesterol drugs, or sedating medications — or antidepressants.

Talk with your doctor or pharmacist about your exact medications before starting this supplement.

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 Feb 25, 2021.

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 L-Theanine, straight from the product label.

Brand SmarterVitamins
Barcode (UPC) X001YTAMAZ
Net contents 50 Softgel(s)
Market status On market
Date entered into DSLD Feb 25, 2021
DSLD ID 243859
Product type Other Combinations
Supplement form Softgel Capsule
Dietary claims / uses Nutrient, All Other, Structure/Function
Intended target group(s) Adult (18 - 50 Years), Dairy Free, Sugar 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 L-Theanine by SmarterVitamins, 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 Softgel(s)
Maximum serving Sizes:
1 Softgel(s)
Servings per container
50
UPC/BARCODE
X001YTAMAZ
IngredientAmount% DV
Flaxseed Oil300 mg--
L-Theanine250 mg--

Other ingredients: Softgel Capsule, Beeswax, Sunflower Lecithin

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

Cleaner. Better. Smarter.

Formula

L-theanine is an amino acid that promotes an alert state of relaxation, and enhances mental clarity & focus. Flaxseed oil provides ALA omega-3 essential fatty acid for an extra source of energy & brain support. L-theanine is derived from green tea which helps moderate occasional stress + anxiety.

Made with flaxseed oil

Formulation

Alertness + Calmness

No BS (Bad Stuff): Corn oil, eggs, milk, wheat, peanut, maltodextrin, soy, lactose, carrageenan, magnesium stearate, dioxides, fillers, sugar, starch, soy bean oil, palm oil, talc or preservatives.

Storage

Store in a cool, dry place away from heat and light.

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.

FDA Statement of Identity

Dietary Supplement

Suggested/Recommended/Usage/Directions

Suggested Use: As a dietary supplement, take 1 softgel 1 to 2 times daily as needed, preferably on an empty stomach.

Precautions

Caution: As with any dietary supplement, consult your healthcare practitioner before using this or any other product if you are pregnant, nursing, trying to conceive, taking medication or have a medical condition.

Keep out of reach of children.

See for yourself

L-Theanine by SmarterVitamins label

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

What’s inside

The Ingredients in L-Theanine by SmarterVitamins

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

Serving size1 Softgel(s) Dosage formSoftgel Capsule Servings per container50 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.

Flaxseed Oil

Interacts with
293 drugs
300 mg per serving

Flaxseed oil is a plant-based source of the omega-3 fatty acid ALA, which the body can partly convert to the omega-3s found in fish oil. It may help s...

Flaxseed Oil monograph & interactions

L-Theanine

Interacts with
565 drugs
250 mg per serving Form: Camellia sinensis

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: Softgel Capsule, Beeswax, Sunflower Lecithin. These complete the product’s ingredient list but are not active constituents.

Interaction report

L-Theanine by SmarterVitamins Drug Interactions

Want to check YOUR meds against L-Theanine?

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
665Drugs
293 Moderate 372 Minor

Ingredients driving the most interactions

Each ingredient & the kinds of drugs it affects

For each ingredient in L-Theanine 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

Flaxseed Oil3 drug types · 293 drugs

Anticoagulant/Antiplatelet Drugs

Theoretically, using flaxseed oil in combination with anticoagulant or antiplatelet drugs might have additive effects and increase the risk of bleeding.
Small clinical studies show that consuming flaxseed oil might decrease platelet aggregation and increase bleeding time.

Likelihood Possible Evidence D
Antihypertensive Drugs

Theoretically, combining flaxseed oil with other antihypertensive drugs might have additive effects and increase the risk of hypotension.
Some clinical evidence suggests that long-term consumption of flaxseed oil can modestly lower systolic and diastolic blood pressure, while other clinical research shows no effect.

Likelihood Possible Evidence D
Ezetimibe (Zetia)

Concomitant use of flaxseed oil and ezetimibe reduces the absorption of alpha-linolenic acid from flaxseed oil.
In one clinical study, concomitant consumption of ezetimibe 10 mg daily with flaxseed oil 2 grams providing 1 gram of alpha-linolenic acid daily blocked the absorption of alpha-linolenic acid, resulting in an overall reduction in alpha-linolenic plasma levels from baseline.

Likelihood Probable Evidence B
The maker

Brand information

Manufacturer and brand details for L-Theanine, from the product label.

SmarterVitamins

See all SmarterVitamins products
Name
SmarterVitamins Corp.
City
Miami
State
FL
ZipCode
33131
Phone Number
888.355.2399
Web Address
smartervitamins.com
Pharmacist Counseling Corner

L-Theanine by SmarterVitamins: Common Questions

Does L-Theanine by SmarterVitamins interact with any medications?
Yes. Based on its ingredients, L-Theanine has a known interaction with 665 medications. Use the checker to see how it interacts with a specific drug.
How can one product interact with so many drugs?
L-Theanine 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.
Will L-Theanine help me focus or improve my memory?
L-theanine may help with cognitive function according to the data we hold, but evidence for age-related memory loss or Alzheimer disease is insufficient to say either way. What this product actually does for memory or focus varies person to person and is best discussed with your doctor.
Is flaxseed oil in this product good for my cholesterol?
No — the evidence rates flaxseed oil as possibly ineffective for high cholesterol. It doesn't appear to help with this use based on the data we have.
Can I take this while pregnant or breastfeeding?
The safety data advises against L-theanine during pregnancy and breastfeeding because there isn't enough information to know it's safe. Flaxseed oil is rated possibly safe in pregnancy, but there's limited information for breastfeeding. Talk with your doctor or pharmacist for personalized advice before using this product if you're pregnant or nursing.
What side effects might L-theanine cause?
Headaches, drowsiness, and increased sleep or dream activity have been reported. These are generally uncommon, and L-theanine is well tolerated in healthy adults for short-term use.
Does flaxseed oil cause digestive issues?
Most people tolerate it well, but a small number report changes in bowel habits, dry mouth, or upset stomach at normal doses. Higher doses (30 grams or more daily) have been linked to loose stools and diarrhea.
Does this product interact with my antidepressant?
L-theanine has a minor, theoretical interaction with serotonergic medications like antidepressants, but no cases of harmful effects have been reported. Still, check the specific drug with your pharmacist or doctor to be sure.

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

Not sure if L-Theanine is safe with your meds?

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Ask a pharmacist

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.

L-Theanine label
Sources

Sources & How We Checked

L-Theanine'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 27 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.

Flaxseed Oil 21 references
  1. Kolonel LN, Nomura AM, Cooney RV. Dietary fat and prostate cancer: current status. J Natl Cancer Inst 1999;91:414-28. PubMed
  2. Ramon JM, Bou R, Romea S, et al. Dietary fat intake and prostate cancer risk: a case-control study in Spain. Cancer Causes Control 2000;11:679-85. PubMed
  3. Nordstrom DC, Honkanen VE, Nasu Y, et al. Alpha-linolenic acid in the treatment of rheumatoid arthritis. A double-blind, placebo-controlled and randomized study: flaxseed vs. safflower seed. Rheumatol Int 1995;14:231-4. PubMed
  4. De Stefani E, Deneo-Pellegrini H, Boffetta P, et al. Alpha-linolenic acid and risk of prostate cancer: a case-control study in Uruguay. Cancer Epidemiol Biomarkers Prev 2000;9:335-8.
  5. Giovannucci E, Rimm EB, Colditz GA, et al. A prospective study of dietary fat and risk of prostate cancer. J Natl Cancer Inst 1993;85:1571-9. PubMed
  6. Bloedon LT, Szapary PO. Flaxseed and cardiovascular risk. Nutr Rev 2004;62:18-27. DOI
  7. Laaksonen DE, Laukkanen JA, Niskanen L, et al. Serum linoleic and total polyunsaturated fatty acids in relation to prostate and other cancers: a population-based cohort study. Int J Cancer 2004;111:444-50.. PubMed
  8. Brouwer IA, Katan MB, Zock PL. Dietary alpha-linolenic acid is associated with reduced risk of fatal coronary heart disease, but increased prostate cancer risk: a meta-analysis. J Nutr 2004;134:919-22.
  9. Paschos GK, Magkos F, Panagiotakos DB, et al. Dietary supplementation with flaxseed oil lowers blood pressure in dyslipidaemic patients. Eur J Clin Nutr 2007;61:1201-6. PubMed
  10. Harper CR, Edwards MC, Jacobson TA. Flaxseed oil supplementation does not affect plasma lipoprotein concentration or particle size in human subjects. J Nutr 2006;136:2844-8. PubMed
  11. University of Montreal. Pregnant Women Consuming Flaxseed Oil Have High Risk Of Premature Birth.ScienceDaily, October 29, 2008. Available at: www.sciencedaily.com/releases/2008/10/081027140817.htm (Accessed May 14, 2009).
  12. Allman, M. A., Pena, M. M., and Pang, D. Supplementation with flaxseed oil versus sunflowerseed oil in healthy young men consuming a low fat diet: effects on platelet composition and function. Eur.J Clin.Nutr. 1995;49(3):169-178.
  13. Ursoniu S, Sahebkar A, Andrica F, Serban C, Banach M; Lipid and Blood Pressure Meta-analysis Collaboration Group. Effects of flaxseed supplements on blood pressure: a systematic review and meta-analysis of controlled clinical trial. Clin Nutr. 2016 Jun;3 PubMed
  14. Taghizadeh M, Jamilian M, Mazloomi M, Sanami M, Asemi Z. A randomized-controlled clinical trial investigating the effect of omega-3 fatty acids on vitamin E co-supplementation on markers of insulin metabolism and lipid profiles in gestational diabetes. J
  15. Blackwood DP, LaVallee RK, Al Busaidi A, Jassal DS, Pierce GN. A randomized trial of the effects of ezetimibe on the absorption of omega-3 fatty acids in cardiac disease patients: a pilot study. Clin Nutr ESPEN. 2015 Oct;10(5):e155-e159. PubMed
  16. Morshedzadeh N, Shahrokh S, Aghdaei HA, et al. Effects of flaxseed and flaxseed oil supplement on serum levels of inflammatory markers, metabolic parameters and severity of disease in patients with ulcerative colitis. Complement Ther Med. 2019;46:36-43. PubMed
  17. Downie LE, Hom MM, Berdy GJ, et al. An artificial tear containing flaxseed oil for treating dry eye disease: A randomized controlled trial. Ocul Surf. 2020;18(1):148-157. PubMed
  18. Saleh-Ghadimi S, Kheirouri S, Golmohammadi A, Moludi J, Jafari-Vayghan H, Alizadeh M. Effect of flaxseed oil supplementation on anthropometric and metabolic indices in patients with coronary artery disease: A double-blinded randomized controlled trial. J PubMed
  19. Jamilian M, Tabassi Z, Reiner Z, et al. The effects of n-3 fatty acids from flaxseed oil on genetic and metabolic profiles in patients with gestational diabetes mellitus: a randomised, double-blind, placebo-controlled trial. Br J Nutr. 2020;123(7):792-799
  20. Li L, Li H, Gao Y, Vafaei S, Zhang X, Yang M. Effect of flaxseed supplementation on blood pressure: a systematic review, and dose-response meta-analysis of randomized clinical trials. Food Funct 2023;14(2):675-690. PubMed
  21. Mahmudiono T, Jasim SA, Karim YS, et al. The effect of flaxseed oil consumption on blood pressure among patients with metabolic syndrome and related disorders: A systematic review and meta-analysis of randomized clinical trials. Phytother Res 2022;36(10):

See these in context on the Flaxseed Oil 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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