21st Century Melatonin 5 mg
vs
Douglas Laboratories Calcium-D-Glucarate
Supplement Comparison

  • Calcium: 21st Century Melatonin 5 mg has 49% more
  • The image below shows:
    • Side-by-side charts with label nutrient amounts, per serving
    • Nutrient forms as listed on the label
    • 4 nutrients compared
Bar chart: per-serving label amounts and listed forms for 21st Century Melatonin 5 mg vs Douglas Laboratories Calcium-D-Glucarate.

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Frequently asked questions

Which active ingredients does 21st Century Melatonin 5 mg have?

  • Calcium appears as Calcium Carbonate
  • Melatonin

Which active ingredients does Douglas Laboratories Calcium-D-Glucarate have?

  • Calcium appears as Calcium as Calcium-D-Glucarate
  • Calcium D-Glucarate

Which categories do 21st Century Melatonin 5 mg and Douglas Laboratories Calcium-D-Glucarate belong to?

  • Sleep Formula
  • Antioxidant Complex

What health concerns do 21st Century Melatonin 5 mg and Douglas Laboratories Calcium-D-Glucarate address?

  • Sleep Quality
  • General Health
  • Liver & Detox Support

Which product has a higher amount of Calcium per serving?

  • 21st Century Melatonin 5 mg has the highest total amount of Calcium: 94 mg per serving

How do the serving sizes compare between the two supplements?

  • Serving size:
    • 21st Century Melatonin 5 mg: 1 tablet
    • Douglas Laboratories Calcium-D-Glucarate: 1 capsule
  • Calcium
    • This supplement has 94 mg
    • Recommended Dietary Allowance in men: 1000 mg
    • Recommended Dietary Allowance in women: 1000 mg
    • Tolerable Upper Intake Level: 2500 mg
  • Calcium
    • This supplement has 63 mg
    • Recommended Dietary Allowance in men: 1000 mg
    • Recommended Dietary Allowance in women: 1000 mg
    • Tolerable Upper Intake Level: 2500 mg

Last updated: February 20, 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.
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  • Author: VIOscan Research Team