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Calcium 500 + D3

21st Century
4.8
★ ★ ★ ★ ★
(8435 ratings)
Calcium 500 mg
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Score96

A natural oyster shell-derived calcium supplement with D3 for efficient and balanced bone support.

How scoring works
Quantity:90 Tablet(s) • (90 servings)
Goals:
Bone Health

Score 96

A natural oyster shell-derived calcium supplement with D3 for efficient and balanced bone support.

How scoring works

Also available as

3 options
400 servings Calcium 500 mg • 400 Tablet(s) • 400 servings $10.99 ($0.02 per serving) 600mg • 75 Tablet(s) servings Calcium 600 mg • 75 Tablet(s) • 75 servings $4.99 ($0.06 per serving) 1000mg • 90 Tablet(s) servings Calcium 1000 mg • 90 Tablet(s) • 90 servings $6.21 ($0.06 per serving)
$5.49($0.06 per serving)
iHerb
$ 5.49
iHerb
$ 4.67
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Analysis

Oyster shell calcium is a natural way to obtain high levels of the mineral in a small serving size. When paired with vitamin D3, as it is here, the body can more effectively utilize the calcium for skeletal support.

The 500mg dose is an excellent amount for a single intake, as it fits within the body's natural absorption window. This makes it a practical and efficient choice for daily supplementation.

Pros

  • Natural oyster shell source
  • Ideal 500mg per serving dose
  • Includes vitamin D3 cofactor
  • Very economical option

Cons

  • Carbonate form needs stomach acid
  • Not suitable for those with shellfish allergies
  • Lacks magnesium balance

Warnings

  • Avoid if you have a shellfish allergy
  • Take with food for optimal absorption

Nutrient quality

88 Highest impact

Inclusion of vitamin D3 enhances the utility of the calcium carbonate source for skeletal support. While bioavailability of the mineral is moderate, the synergistic pairing is appropriate for maintenance.

Ingredient transparency

99 Highest impact

Labeling clearly identifies the oyster shell source and quantifies the active components. Consumer transparency is supported by clear intake instructions and disclosure of excipients.

Customer satisfaction

97 Highest impact

Superior user ratings from a massive demographic confirm the product's reliability and quality. Feedback indicate high satisfaction with the perceived benefits and affordable nature of the supplement.

Value for money

100 Highest impact

Pricing is exceptionally low for a synergistic mineral and vitamin supplement. High serving value makes this a top choice for budget-conscious users seeking skeletal support.

Report analysis

Goals

Bone Health
Impact
High effect
A- Goal FitB Strength of SupportC CoverageA Formula Quality

Oyster shell-derived calcium provides a foundational structural mineral required for maintaining skeletal density and strength. Vitamin D3 is included to maximize the intestinal absorption and transport of calcium to the bone matrix.

The use of carbonate from oyster shells is less bioavailable than organic chelates and requires adequate stomach acid for effectiveness. This formula lacks structural magnesium and signaling cofactors like vitamin K2, which limits its comprehensive skeletal support.

View goal →

Ingredients

IngredientAmount per serving
Vitamin D3 (Cholecalciferol)
 15 mcg
Calcium (Oyster Shell)
 500 mg
Gluten Free Adults 18–50
Report overview
Calcium (Oyster Shell) · 500 mg OverallScore80
C+ Active Ingredient Quality & BioavailabilityB+ Dose, Safety & Label TransparencyA+ Value
This oyster shell-derived calcium supplement delivers 500 mg of mineral carbonate paired with vitamin D3. It is a foundational choice for daily bone health support at a very competitive price.
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