21st Century Vitamin C
vs
Metagenics Ultra Potent-C Vitamin C
Supplement Comparison

  • Vitamin C: 21st Century Vitamin C has 2.0× more
  • The image below shows:
    • Side-by-side charts with label nutrient amounts, per serving
    • Nutrient forms as listed on the label
    • 8 nutrients compared
Bar chart: per-serving label amounts and listed forms for 21st Century Vitamin C vs Metagenics Ultra Potent-C Vitamin C.

Frequently asked questions

Which active ingredients does 21st Century Vitamin C have?

  • Vitamin C appears as Ascorbic Acid
  • Calcium appears as Calcium Carbonate

Which active ingredients does Metagenics Ultra Potent-C Vitamin C have?

  • Vitamin C appears as Ascorbic Acid
  • Vitamin B3 (Niacin) appears as Nicotinic Acid
  • L-Lysine appears as L-Lysine Monohydrochloride
  • Citrus Bioflavonoid Complex

Which categories do 21st Century Vitamin C and Metagenics Ultra Potent-C Vitamin C belong to?

  • Single Vitamin

What health concerns do 21st Century Vitamin C and Metagenics Ultra Potent-C Vitamin C address?

  • Antioxidant Support
  • Immune System Support

Which product has a higher amount of Vitamin C per serving?

  • 21st Century Vitamin C has the highest total amount of Vitamin C: 500 mg per serving

How do the serving sizes compare between the two supplements?

  • Serving size:
    • 21st Century Vitamin C: 1 tablet
    • Metagenics Ultra Potent-C Vitamin C: 1 tablet
  • Vitamin C
    • This supplement has 500 mg
    • Recommended Dietary Allowance in men: 90 mg
    • Recommended Dietary Allowance in women: 75 mg
    • Tolerable Upper Intake Level: 2000 mg
  • Calcium
    • This supplement has 30 mg
    • Recommended Dietary Allowance in men: 1000 mg
    • Recommended Dietary Allowance in women: 1000 mg
    • Tolerable Upper Intake Level: 2500 mg
  • Vitamin C
    • This supplement has 250 mg
    • Recommended Dietary Allowance in men: 90 mg
    • Recommended Dietary Allowance in women: 75 mg
    • Tolerable Upper Intake Level: 2000 mg
  • Vitamin B3 (Niacin)
    • This supplement has 17.5 mg
    • Recommended Dietary Allowance in men: 16 mg
    • Recommended Dietary Allowance in women: 14 mg
    • Tolerable Upper Intake Level: 35 mg

Last updated: January 2, 2026

  • Sources & Methodology: Nutrient data and forms are taken directly from Supplement Facts labels. Reviewed and standardized by the VIOscan Research Team. Learn more on the Methodology page.
  • We show the Recommended Dietary Allowance (RDA) when available. If no RDA exists, we show the Adequate Intake (AI). Tolerable Upper Intake Levels (UL) are used for upper limits. Unless otherwise noted, RDAs shown correspond to healthy adults aged 19–50 years and are sex-specific. Separate values exist for 51–70 years and >70 years, and pregnancy and lactation are excluded. All values come from the Dietary Reference Intakes (DRIs) published by the National Academies of Sciences, Engineering, and Medicine (NASEM), Food and Nutrition Board (FNB).
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  • Editorial standards: we provide independent, impartial and objective data analysis.
  • This analysis is for educational purposes only. It is not a substitute for medical advice.
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  • Author: VIOscan Research Team