21st Century Vitamin B-12 1000 mcg
vs
Klean Athlete Klean B Complex
Supplement Comparison

  • Vitamin B12 (Cobalamin): 21st Century Vitamin B-12 1000 mcg has 25% more
  • The image below shows:
    • Side-by-side charts with label nutrient amounts, per serving
    • Nutrient forms as listed on the label
    • 22 nutrients compared
Bar chart: per-serving label amounts and listed forms for 21st Century Vitamin B-12 1000 mcg vs Klean Athlete Klean B Complex.

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Frequently asked questions

Which active ingredients does 21st Century Vitamin B-12 1000 mcg have?

  • Vitamin B12 (Cobalamin) appears as Cyanocobalamin
  • Calcium appears as Calcium Carbonate

Which active ingredients does Klean Athlete Klean B Complex have?

  • Vitamin B1 (Thiamin) appears as Thiamin HCl
  • Vitamin B1 (Thiamin) appears as BenfoPure Benfotiamine
  • Vitamin B2 (Riboflavin) appears as Riboflavin and Riboflavin-5-Phosphate (activated B2)
  • Vitamin B3 (Niacin) appears as Niacinamide
  • Vitamin B6 (Pyridoxine) appears as Pyridoxine HCl and Pyridoxal-5-Phosphate (activated B6)
  • Vitamin B9 (Folate) appears as Metafolin L-5-MTHF
  • Vitamin B12 (Cobalamin) appears as Adenosylcobalamin and Hydroxycobalamin
  • Vitamin B7 (Biotin) appears as D-Biotin
  • Vitamin B5 (Pantothenic Acid) appears as Calcium Pantothenate
  • Choline appears as Choline Bitartrate
  • Inositol

Which categories do 21st Century Vitamin B-12 1000 mcg and Klean Athlete Klean B Complex belong to?

  • Single Vitamin
  • B-Complex Formula

What health concerns do 21st Century Vitamin B-12 1000 mcg and Klean Athlete Klean B Complex address?

  • General Health
  • Brain, Focus & Cognitive Function
  • Energy & Metabolism
  • Methylation Support

Which product has a higher amount of Vitamin B12 (Cobalamin) per serving?

  • 21st Century Vitamin B-12 1000 mcg has the highest total amount of Vitamin B12 (Cobalamin): 1000 mcg per serving

How do the serving sizes compare between the two supplements?

  • Serving size:
    • 21st Century Vitamin B-12 1000 mcg: 1 tablet
    • Klean Athlete Klean B Complex: 1 capsule
  • Vitamin B12 (Cobalamin)
    • This supplement has 1000 mcg
    • Recommended Dietary Allowance in men: 2.4 mcg
    • Recommended Dietary Allowance in women: 2.4 mcg
    • Tolerable Upper Intake Level: Not established
  • Calcium
    • This supplement has 100 mg
    • Recommended Dietary Allowance in men: 1000 mg
    • Recommended Dietary Allowance in women: 1000 mg
    • Tolerable Upper Intake Level: 2500 mg
  • Vitamin B1 (Thiamin)
    • This supplement has 28 mg
    • Recommended Dietary Allowance in men: 1.2 mg
    • Recommended Dietary Allowance in women: 1.1 mg
    • Tolerable Upper Intake Level: Not established
  • Vitamin B2 (Riboflavin)
    • This supplement has 15 mg
    • Recommended Dietary Allowance in men: 1.3 mg
    • Recommended Dietary Allowance in women: 1.1 mg
    • Tolerable Upper Intake Level: Not established
  • Vitamin B3 (Niacin)
    • This supplement has 50 mg
    • Recommended Dietary Allowance in men: 16 mg
    • Recommended Dietary Allowance in women: 14 mg
    • Tolerable Upper Intake Level: 35 mg
  • Vitamin B6 (Pyridoxine)
    • This supplement has 50 mg
    • Recommended Dietary Allowance in men: 1.3 mg
    • Recommended Dietary Allowance in women: 1.3 mg
    • Tolerable Upper Intake Level: 100 mg
  • Vitamin B9 (Folate)
    • This supplement has 1333 mcg DFE
    • Recommended Dietary Allowance in men: 400 mcg DFE
    • Recommended Dietary Allowance in women: 400 mcg DFE
    • Tolerable Upper Intake Level: 1000 mcg DFE
  • Vitamin B12 (Cobalamin)
    • This supplement has 800 mcg
    • Recommended Dietary Allowance in men: 2.4 mcg
    • Recommended Dietary Allowance in women: 2.4 mcg
    • Tolerable Upper Intake Level: Not established

Last updated: February 5, 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).
  • Transparency: We’re funded by our users. We don’t have sponsors or affiliate links, and we don’t sell supplements.
  • 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.
  • Questions? Read our Frequently Asked Questions or contact us, we’re here to help.
  • See an error? Report it through our Contact page.
  • Author: VIOscan Research Team