21st Century Prolonged Release Niacin, 500 mg, 100 Tablets supplement bottle
21st Century

Prolonged Release Niacin, 500 mg, 100 Tablets

What We Researched
1 active ingredient analyzed · 9 inactive ingredients decoded · 2 brand certifications checked · 2 retailers compared · Last updated: Mar 2026
88
Product Score Good
76
Brand Score Fair

Product Analysis

Transparency Excellent

Supplement Facts

IngredientAmount% DV
Niacin 500 mg 3,125%
Bioavailability Excellent

Absorption Rating

  • Niacin Good
Other Ingredients Very Good

Fillers & Additives

  • Cellulose
  • Hydroxypropyl Methylcellulose
  • Stearic Acid
  • Magnesium Silicate
  • Magnesium Stearate
  • Polyethylene Glycol Low
  • Polysorbate Medium
  • Polyvinyl Alcohol
  • Silicon Dioxide
Efficacy Very Good

Dosage Analysis

  • Niacin 500 mg High

Supplement Facts

Ingredient Amount % Daily Value
Niacin 500 mg 3,125%

Other Ingredients

Inactive ingredients used in manufacturing. All rated for safety.

Cellulose Safe

Provides bulk and structure in tablets and capsules.

Hydroxypropyl Methylcellulose Safe

It is used as a coating for tablets and capsules.

Stearic Acid Safe

Helps ingredients flow smoothly through manufacturing equipment.

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.

Polysorbate Generally_safe

It is used to help mix oil and water-based ingredients.

Polyvinyl Alcohol Generally_safe

It is used as a coating for tablets or capsules.

Silicon Dioxide Safe

Prevents clumping and ensures consistent dosing.

Price Comparison

Price History

Tracked across major retailers. Updated periodically.

$10$9$8$7$6 Mar 12 $7.64
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 Prolonged Release Niacin, 500 mg a good supplement?

21st Century Prolonged Release Niacin, 500 mg, 100 Tablets received a product quality score of 88/100 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 1 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 Prolonged Release Niacin, 500 mg?

21st Century Prolonged Release Niacin, 500 mg contains 1 active ingredients: Niacin (500 mg). Notable high-dose ingredients include Niacin at 3,125% DV. Each ingredient's dosage, form, and safety rating is analyzed independently in GoodSupp's full product breakdown.

Is 21st Century Prolonged Release Niacin, 500 mg safe to take?

21st Century Prolonged Release Niacin, 500 mg, 100 Tablets has been analyzed for ingredient safety across all its components. Of 9 inactive ingredients, 5 are rated safe. 1 ingredient is flagged for review: Polyethylene Glycol. '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.

How much vitamin d3 should i take daily?

The optimal dosage depends on your individual health needs, age, sex, and current nutrient levels. Recommended daily amounts are established by health authorities but may vary from therapeutic doses used in clinical research. It's important to check the Supplement Facts label for the exact amount per serving and compare it against the % Daily Value. Some supplements provide mega-doses well above the Daily Value, which may not be necessary and in some cases could be harmful — particularly for fat-soluble vitamins (A, D, E, K) that accumulate in the body. GoodSupp's efficacy analysis evaluates whether a product's dosages align with clinically studied amounts. Always consult your healthcare provider for personalized dosage recommendations.

What does vitamin d do?

This is an important question for supplement consumers. The dietary supplement industry is largely self-regulated, which means product quality, ingredient transparency, and safety practices vary significantly between brands and products. The most reliable way to evaluate any supplement is to check for third-party testing certifications, review the full ingredient list and dosages, and research the brand's regulatory track record. GoodSupp's database of over 250,000 analyzed products provides independent quality scores, ingredient safety ratings, and brand trust reports to help you make evidence-based decisions.

How much vitamin d3 per day for a woman?

The optimal dosage depends on your individual health needs, age, sex, and current nutrient levels. Recommended daily amounts are established by health authorities but may vary from therapeutic doses used in clinical research. It's important to check the Supplement Facts label for the exact amount per serving and compare it against the % Daily Value. Some supplements provide mega-doses well above the Daily Value, which may not be necessary and in some cases could be harmful — particularly for fat-soluble vitamins (A, D, E, K) that accumulate in the body. GoodSupp's efficacy analysis evaluates whether a product's dosages align with clinically studied amounts. Always consult your healthcare provider for personalized dosage recommendations.

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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.