Comparison

C 500 and C 500 mg

C 500 (21st Century) lists 2 distinct ingredients and C 500 mg (21st Century) 2 (rows of one ingredient counted once); 2 are on both labels. On the site's similarity measure, which compares ingredient lists (1 for the same list, rarer ingredients counting for more; amounts are not part of it), the two formulas score 1.00: the same ingredients, at the amounts in the table below.

Amount per serving (and % of the Daily Value)
Ingredient	C 500	C 500 mg
Vitamin C	500 mg (556%)	500 mg (556%)
Calcium	30 mg (2%)	30 mg (2%)

Amounts are per serving as DSLD gives them: C 500, 1 tablet; C 500 mg, 1 tablet. Current labels entered August 2020 and October 2021. Percentages of the Daily Value from 21 CFR 101.9. Source: NIH ODS Dietary Supplement Label Database.

Each product on its own

C 50021st Century: every row against all products listing it
C 500 mg21st Century: every row against all products listing it