21st Century L-Lysine, 1,000 mg, 90 Tablets supplement bottle
21st Century

L-Lysine, 1,000 mg, 90 Tablets

What We Researched
1 active ingredient analyzed · 9 inactive ingredients decoded · 2 brand certifications checked · 3 retailers compared · Last updated: Mar 2026
86
Product Score Good
76
Brand Score Fair

Product Analysis

Transparency Excellent

Supplement Facts

IngredientAmount% DV
L-Lysine (as L-Lysine Hydrochloride) 1,000 mg **
Bioavailability Excellent

Absorption Rating

  • L-Lysine (as L-Lysine Hydrochloride) Good
Other Ingredients Good

Fillers & Additives

  • Cellulose
  • Stearic Acid
  • Croscarmellose Sodium
  • Magnesium Silicate
  • Magnesium Stearate
  • Polyethylene Glycol Low
  • Polyvinyl Alcohol
  • Silicon Dioxide
  • Titanium Dioxide High
Efficacy Excellent

Dosage Analysis

  • L-Lysine (as L-Lysine Hydrochloride) 1,000 mg Effective

Supplement Facts

Ingredient Amount % Daily Value
L-Lysine (as L-Lysine Hydrochloride) 1,000 mg **

Other Ingredients

Inactive ingredients used in manufacturing. All rated for safety.

Cellulose Safe

Provides bulk and structure in tablets and capsules.

Stearic Acid Safe

Helps ingredients flow smoothly through manufacturing equipment.

Croscarmellose Sodium Safe

Helps tablets break apart and dissolve quickly in the stomach.

Magnesium Silicate Generally_safe

It is used to improve powder flow and prevent clumping.

Magnesium Stearate Safe

Prevents ingredients from sticking to manufacturing equipment during tableting.

Polyethylene Glycol Caution

It is used as a binder, coating agent, or to improve solubility.

Polyvinyl Alcohol Generally_safe

It is used as a coating for tablets or capsules.

Silicon Dioxide Safe

Prevents clumping and ensures consistent dosing.

Titanium Dioxide Caution

Used as a whitening agent in tablet coatings and capsules.

Price Comparison

iHerb $6.74
Best Price
Target $12.06

Price History

Tracked across major retailers. Updated periodically.

$8$7$6$5$4 Mar 12 $6.00
iHerb

Prices shown at time of last check. Click a retailer to see current price. GoodSupp is not affiliated with any retailer.

Brand Trust Report
21st Century

Founded 1991 · Tempe, Arizona, United States · 231 products · 21stcenturyvitamins.com/

Certifications

2 certifications
Consumerlab Verified
Nsf Gmp Verified Source

Transparency

4 claims
Third Party Testing Claim — Claimed Source
Testing Lab Disclosure — Verified Source
In House Testing — Verified Source

Violation History

4 incidents
Prop 65 Lead2021-06-22Source
Recall Vitamin D3 5000 IU Tablets2021-05-19Source
Lawsuit False advertising of Glucosamine/Chondroitin supplements.2012Source
Prop 65 Lead2008-12-23Source
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Frequently Asked Questions
Is 21st Century L-Lysine, 1 a good supplement?

21st Century L-Lysine, 1,000 mg, 90 Tablets received a product quality score of 86/100 in GoodSupp's independent analysis, indicating strong overall quality. The product contains 1 active ingredients Of the 9 inactive ingredients, 5 are rated safe and 2 are flagged for review. The manufacturer, 21st Century, holds a brand trust score of 76/100 with 2 verified certifications including Consumerlab, Nsf Gmp.

What are the ingredients in 21st Century L-Lysine, 1?

21st Century L-Lysine, 1 contains 1 active ingredients: L-Lysine (as L-Lysine Hydrochloride) (1,000 mg). Each ingredient's dosage, form, and safety rating is analyzed independently in GoodSupp's full product breakdown.

Is 21st Century L-Lysine, 1 safe to take?

21st Century L-Lysine, 1,000 mg, 90 Tablets has been analyzed for ingredient safety across all its components. Of 9 inactive ingredients, 5 are rated safe. 2 ingredients are flagged for review: Polyethylene Glycol, Titanium Dioxide. 'Caution' doesn't mean dangerous — it indicates the ingredient has some considerations worth being aware of, such as potential sensitivities or ongoing research. Always consult your healthcare provider before starting any new supplement, especially if you take medications or have underlying health conditions.

Is 21st Century a trustworthy supplement brand?

21st Century receives a brand trust score of 76/100 based on GoodSupp's independent analysis of certifications, regulatory history, and transparency practices. Founded in 1991 and headquartered in Tempe, Arizona, United States, the company offers 231 products in their lineup. They hold 2 verified certifications including Consumerlab, Nsf Gmp. Third-party certifications are independently verified and indicate the brand meets specific quality, purity, and manufacturing standards. Note: 21st Century has 4 historical regulatory incidents on record, which are factored into the trust score.

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Disclaimer: GoodSupp provides independent supplement quality analysis for informational purposes only. Scores are generated algorithmically based on ingredient profiles, brand certifications, and public records. This is not medical advice. Always consult a healthcare professional before starting any supplement regimen. Product data is sourced from manufacturer labels and public databases. GoodSupp is not affiliated with any supplement brand.