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Dietary supplement

L-Phenylalanine Ingredients & Drug Interactions

by BulkSupplements.com

L-Phenylalanine label
See full label image
Powder Category: Amino Acid/protein
Most serious interaction: Major
Clinical methodology reviewed by · Updated Sep 16, 2026 · Label data from the NIH DSLD
What is this page for?

First and foremost: checking L-Phenylalanine 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: Major

L-Phenylalanine is a dietary supplement by BulkSupplements.com with 1 active ingredient. Its ingredients are commonly taken for depression and mood, skin condition vitiligo, pain conditions.Based on those ingredients, 16 medications have a known interaction with it, the most serious rated major. The ingredients most likely to interact are L-Phenylalanine. Use the checker below to test your specific medication, or read the full HelloPharmacist Interaction Report.

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Check Your Meds Against L-Phenylalanine by BulkSupplements.com

Ask about any prescription or over-the-counter medication and we check it for interactions with L-Phenylalanine by BulkSupplements.com — and tell you which ingredient is responsible.

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HelloPharmacist Scorecard of L-Phenylalanine by BulkSupplements.com

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 Aug 13, 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 is pure L-phenylalanine, a single amino acid. It's one of the nine essential amino acids your body can't make on its own — you normally get it from protein in food.

The powder form lets you add it to drinks or mix it into food.

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 Phenylalanine's overall clinical evidence instead.

Moderate

Some clinical evidence supports Phenylalanine 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: Vitiligo — rated "Possibly Effective" (Natural Medicines).

L-Phenylalanine is rated possibly effective for vitiligo (a skin pigmentation condition). For ADHD, the evidence suggests it's possibly ineffective.

For alcohol use disorder and multiple sclerosis, we don't have enough reliable evidence to say whether it works.

The evidence, ingredient by ingredient Phenylalanine

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.

L-Phenylalanine is generally well tolerated at typical doses in food amounts, but supplements should be used carefully. If you have PKU (phenylketonuria), avoid it entirely — your body can't clear phenylalanine properly, and it builds up to dangerous levels.

The most common side effects when taken by mouth are anxiety, constipation, headache, heartburn, insomnia, nausea, and sedation. Rarely, it's been linked to hypomania.

Avoid supplement doses during pregnancy and while breastfeeding — safety data isn't established for those situations. Talk with your doctor or pharmacist about whether this is right for you if you're pregnant, planning to become pregnant, or nursing.

Side effects, ingredient by ingredient Phenylalanine

Meds to double-check

Major interaction found
Known Interaction Concern · database check
Major identified

At least one ingredient has a documented Major-severity interaction. Check your medications for a personalized result.

Why this rating?
  • 1 of the 1 matched ingredient can interact with medications — Phenylalanine.
  • The most serious interaction on file is rated Major.
  • Some involve high-stakes drug classes: Parkinson's medications.
  • For scale: 16 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 L-Phenylalanine, check with your doctor or pharmacist if you take levodopa (Parkinson disease) — it's a Major interaction that can worsen your symptoms. Also confirm you don't take baclofen or an MAOI antidepressant, both of which have Moderate interactions with this supplement.

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. Major medication interactions have been identified, and safety information is well characterized.

L-Phenylalanine may be worth considering if you have vitiligo, but it's not your answer for ADHD. The biggest caution: it interacts with levodopa (Parkinson's), baclofen (muscle relaxant), and MAOIs (certain antidepressants), so check your medications first.

If you have PKU, skip it entirely. Run your drug list through our tool and talk it over with your doctor or pharmacist before you start.

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 Apr 23, 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 L-Phenylalanine, straight from the product label.

Brand BulkSupplements.com
Barcode (UPC) X000J3OWXF
Net contents 250 Gram(s); 8.8 Ounce(s)
Market status On market
Date entered into DSLD Apr 23, 2024
DSLD ID 312215
Product type Amino Acid/protein
Supplement form Powder
Dietary claims / uses All Other, Structure/Function
Intended target group(s) Adult (18 - 50 Years), 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 L-Phenylalanine by BulkSupplements.com, 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:
500 mg
Maximum serving Sizes:
500 mg
Servings per container
500
UPC/BARCODE
X000J3OWXF
IngredientAmount% DV
L-Phenylalanine500 mg--

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.
Brand IP Statement(s)

BulkSupplements.com Clean & Pure Bulk Supplements

FDA Disclaimer Statement

Warning: This product is not intended to diagnose, treat, cure, or prevent any disease.

Precautions

Always consult a physician before taking any dietary supplement.

Keep out of reach of children.

Formulation

Free of: Added sugar, soy, dairy, yeast, gluten, additives

Suggested/Recommended/Usage/Directions

Suggested use: As a dietary supplement, take 500 mg (about 1/5 tsp) one to three times daily, or as directed by a physician.

Storage

Store in a dry, cool place

General Statements

Use an accurate milligram scale. Contents are sold by weight, not volume. Settling may occur. New

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

See for yourself

L-Phenylalanine by BulkSupplements.com label

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

L-Phenylalanine 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 L-Phenylalanine by BulkSupplements.com

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

Serving size500 mg Dosage formPowder Servings per container500 Amounts shown are per serving.

L-Phenylalanine

Interacts with
16 drugs
500 mg per serving

Phenylalanine is an essential amino acid the body uses to make brain chemicals like dopamine and norepinephrine. Some people take it for mood, vitilig...

L-Phenylalanine monograph & interactions
Interaction report

L-Phenylalanine by BulkSupplements.com Drug Interactions

Want to check YOUR meds against L-Phenylalanine?

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
16Drugs
5 Major 11 Moderate

Ingredients driving the most interactions

L-Phenylalanine 16

Individual Drug Interactions

The ingredients in L-Phenylalanine interact with 16 drugs. Click any drug to see the details.

1 of the 1 ingredient in L-Phenylalanine interact with drugs. Each result below shows which ingredient is responsible. L-Phenylalanine

Each ingredient & the kinds of drugs it affects

For each ingredient in L-Phenylalanine 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.

L-Phenylalanine3 drug types · 16 drugs

Levodopa

Phenylalanine, especially in high doses, can reduce the effectiveness of levodopa.
Phenylalanine competes with levodopa for carrier-mediated transport into the brain. The resulting reduction in levels of levodopa in the brain can exacerbate tremor, rigidity, and the "on-off" phenomenon in patients with Parkinson disease.

Likelihood Probable Evidence B
Baclofen

Concomitant intake of phenylalanine may reduce the intestinal absorption of baclofen.
Phenylalanine and baclofen share the same intestinal carrier for absorption; phenylalanine competitively inhibits the absorption of baclofen, reducing its plasma levels.

Likelihood Possible Evidence D
Monoamine Oxidase Inhibitors (Maois)

Theoretically, concomitant use of L-phenylalanine and non-selective MAOIs might increase the risk of hypertensive crisis.
L-phenylalanine is metabolized to tyrosine. Some evidence suggests that L-phenylalanine, given with the non-selective MAOI pargyline, might prevent the elimination of tyramine, increasing the risk of hypertensive crisis. However, this was not reported in a small number of patients when using L-phenylalanine with the partially selective MAO-B inhibitor, selegiline.

Likelihood Possible Evidence D
L-Phenylalanine full monograph & interactions
The maker

Brand information

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

BulkSupplements.com

See all BulkSupplements.com products
Name
BulkSupplements.com
Street Address
7511 Eastgate Rd
City
Henderson
State
NV
ZipCode
89011
Web Address
BulkSupplements.com
Pharmacist Counseling Corner

L-Phenylalanine by BulkSupplements.com: Common Questions

Does L-Phenylalanine by BulkSupplements.com interact with any medications?
Yes. Based on its ingredients, L-Phenylalanine has a known interaction with 16 medications, including 5 rated major. Use the checker to see how it interacts with a specific drug.
How can one product interact with so many drugs?
L-Phenylalanine 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.
Can I take L-Phenylalanine if I'm pregnant?
Safety hasn't been established in pregnancy, so avoid supplement doses. Talk with your doctor or pharmacist for personalized advice if you're pregnant or planning to become pregnant.
Can I take L-Phenylalanine while breastfeeding?
Safety data is lacking for breastfeeding, so it's best to avoid supplement doses. Check with your doctor or pharmacist before taking it while nursing.
Does L-Phenylalanine work for ADHD?
No. The evidence suggests it's possibly ineffective for ADHD, so it's not a reliable option for that use.
What's L-Phenylalanine for?
It's an amino acid your body needs. The evidence is strongest for vitiligo (a skin pigmentation condition), where it's rated possibly effective. You normally get it from protein in food, but some people take supplements.
What are the common side effects?
The most common are anxiety, constipation, headache, heartburn, insomnia, nausea, and sedation. Rarely, it's been linked to hypomania. Most people tolerate it well at typical doses.
Can I take this if I have PKU?
No. PKU is a genetic condition where your body can't clear phenylalanine, so it builds up dangerously. Avoid this supplement entirely.

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

Not sure if L-Phenylalanine 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.

L-Phenylalanine label
Go deeper

The Full Monographs Behind L-Phenylalanine’s Ingredients

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

Herb & supplement monograph

Phenylalanine

Interacts with 16 drugs

Phenylalanine is an essential amino acid the body uses to make brain chemicals like dopamine and norepinephrine. Some people take it for mood, vitiligo, or pain, but the evidence is mostly l...

Read the full Phenylalanine monograph →
Sources

Sources & How We Checked

L-Phenylalanine'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 23 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.

Phenylalanine 23 references
  1. Rouse B, Azen C, Koch R, et al. Maternal phenylketonuria collaborative Study (MPKUCS) offspring: facial anomalies, malformations, and early neurological sequelae. Am J Med Genet 1997;69:89-95. DOI
  2. Sturtevant FM. Use of aspartame in pregnancy. Int J Fertil 1985;30:85-7.
  3. Silkaitis RP, Mosnaim AD. Pathways linking L-phenylalanine and 2-phenylethylamine with p-tyramine in rabbit brain. Brain Res 1976;114:105-15.
  4. Lehmann WD, Theobald N, Fischer R, Heinrich HC. Stereospecificity of phenylalanine plasma kinetics and hydroxylation in man following oral application of a stable isotope-labelled pseudo-racemic mixture of L- and D-phenylalanine. Clin Chim Acta 1983;128 PubMed
  5. Mosnik DM, Spring B, Rogers K, Baruah S. Tardive dyskinesia exacerbated after ingestion of phenylalanine by schizophrenic patients. Neuropsychopharmacology 1997;16:136-46. PubMed
  6. Siddiqui AH, Stolk LM, Bhaggoe R, et al. L-phenylalanine and UVA irradiation in the treatment of vitiligo. Dermatology 1994;88:215-8. PubMed
  7. Birkmayer W, Riederer P, Linauer W, Knoll J. L-deprenyl plus L-phenylalanine in the treatment of depression. J Neural Transm 1984;59:81-7. PubMed
  8. Nutt JG, Woodward WR, Hammerstad JP, et al. The "on-off" phenomenon in Parkinson's disease. Relation to levodopa absorption and transport. N Engl J Med 1984;310:483-8. PubMed
  9. Baruzzi A, Contin M, Riva R, et al. Influence of meal ingestion time on pharmacokinetics of orally administered levodopa in parkinsonian patients. Clin Neuropharmacol 1987;10:527-37. PubMed
  10. Juncos JL, Fabbrini G, Mouradian MM, et al. Dietary influences on the antiparkinsonian response to levodopa. Arch Neurol 1987;44:1003-5. PubMed
  11. Eriksson T, Granerus AK, Linde A, et al. "On-off" phenomenon in Parkinson's disease: relationship between dopa and other large neutral amino acids in plasma. Neurology 1988;38:1245-8. PubMed
  12. Baker GB, Bornstein RA, Rouget AC, et al. Phenylethylaminergic mechanisms in attention-deficit disorder. Biol Psychiatry 1991;29:15-22.. PubMed
  13. Wood DR, Reimherr FW, Wender PH. Treatment of attention deficit disorder with DL-phenylalanine. Psychiatry Res 1985;16:21-6.. PubMed
  14. Food and Nutrition Board, Institute of Medicine. Dietary Reference Intakes for Energy, Carbohydrate, Fiber, Fat, Fatty Acids, Cholesterol, Protein, and Amino Acids (Macronutrients). Washington, DC: National Academy Press, 2002. Available at: http://www.n
  15. Cederbaum S. Phenylketonuria: an update. Curr Opin Pediatr 2002;14:702-6. PubMed
  16. Cejudo-Ferragud, E., Nacher, A., Polache, A., Cercos-Fortea, T., Merino, M., and Casabo, V. G. Evidence of competitive inhibition for the intestinal absorption of baclofen by phenylalanine. Int J of Pharm (Amsterdam) 1996;132:63-69. DOI
  17. Fischer, E., Heller, B., Nachon, M., and Spatz, H. Therapy of depression by phenylalanine. Preliminary note. Arzneimittelforschung. 1975;25(1):132.
  18. Beckmann, H., Strauss, M. A., and Ludolph, E. Dl-phenylalanine in depressed patients: an open study. J.Neural Transm. 1977;41(2-3):123-134. PubMed
  19. Sabelli, H. C., Fawcett, J., Gusovsky, F., Javaid, J. I., Wynn, P., Edwards, J., Jeffriess, H., and Kravitz, H. Clinical studies on the phenylethylamine hypothesis of affective disorder: urine and blood phenylacetic acid and phenylalanine dietary supplem
  20. Cotzias, G. C., Van Woert, M. H., and Schiffer, L. M. Aromatic amino acids and modification of parkinsonism. N Engl.J Med 2-16-1967;276(7):374-379. PubMed
  21. Kravitz, H. M., Sabelli, H. C., and Fawcett, J. Dietary supplements of phenylalanine and other amino acid precursors of brain neuroamines in the treatment of depressive disorders. J Am Osteopath.Assoc 1984;84(1 Suppl):119-123. DOI
  22. Mann, J., Peselow, E. D., Snyderman, S., and Gershon, S. D-phenylalanine in endogenous depression. Am.J.Psychiatry 1980;137(12):1611-1612. PubMed
  23. Katoulis AC, Alevizou A, Bozi E, et al. A randomized, double-blind, vehicle-controlled study of a preparation containing undecylenoyl phenylalanine 2% in the treatment of solar lentigines. Clin Exp Dermatol 2010;35(5):473-6. PubMed

See these in context on the Phenylalanine 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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