Vitamin C
Ascorbic Acid
Water-soluble antioxidant vitamin. FDA RDI for adults 4+ is 90 mg per day. Common forms: ascorbic acid, sodium ascorbate, calcium ascorbate.
FDA Reference Data
About Vitamin C
Vitamin C (ascorbic acid) is a voluntary-declaration vitamin per FDA 21 CFR 101.36(b)(2). FDA RDI is 90 mg/day for adults 4+. Both natural and synthetic forms are bioequivalent. Supplement Facts labels declare "Vitamin C" with the amount in mg; the specific form (ascorbic acid, sodium ascorbate, etc.) appears in the ingredient list. Per 21 CFR 101.36(b)(2)(iii), vitamin C amounts ≥ 10 mg round to the nearest 1 mg; < 10 mg rounds to 0.1 mg.
Common Supplement Forms
Note: When a salt form is used, the Supplement Facts panel must declare the elemental amount (e.g., “Magnesium 141 mg 34%”), not the salt weight. The salt name appears in the ingredient list below the panel. See %DV calculator for calculation details.
Frequently Asked Questions
What is the FDA RDI for Vitamin C?
The FDA RDI for Vitamin C is 90 mg per day for adults and children 4 years and older (21 CFR 101.9(c)(8)(iv)). This value reflects the Recommended Dietary Allowance (RDA) for non-smoking adult males. %DV is calculated as: (declared mg / 90) × 100, rounded to the nearest whole percent.
How do I declare buffered Vitamin C (sodium ascorbate) on my label?
On the Supplement Facts panel, declare "Vitamin C [amount] mg [%DV]" using the elemental ascorbic acid equivalent. The form "Sodium Ascorbate" appears in the ingredient list below. If the product contains sodium ascorbate, the sodium contribution should also be declared on the "Sodium" line of the Supplement Facts panel (per 21 CFR 101.36(b)(2)).
What are the FDA rounding rules for Vitamin C?
Per 21 CFR 101.36(b)(2)(iii): Vitamin C amounts < 10 mg round to the nearest 0.1 mg; 10-99 mg round to the nearest 1 mg; ≥ 100 mg round to the nearest 10 mg. For example, 1.45 mg → 1.5 mg; 67.3 mg → 67 mg; 523 mg → 520 mg. Trailing zeros (e.g., "10.0 mg") are non-compliant unless aligned with the rounding increment.
Related Solutions
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