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Every Ester-C serving is 1,000 mg of vitamin C as calcium ascorbate. Compare the six formulas

Learn: vitamin C with Ester-C

Three articles on vitamin C from the people who make Ester-C: daily needs, buffered vitamin C, and the label.

Ester-C day-cycle illustration: a city at sunrise

How Much Vitamin C Do You Need a Day? The NIH Numbers, Plainly

Most adults in the United States need 75 or 90 mg of vitamin C a day, and one serving of our tablets holds 1,000 mg.

Ester-C boxes and a bottle on a marigold table with an orange and a flask

Buffered Vitamin C: What Calcium Ascorbate Is and What Ester-C Adds

If plain vitamin C tablets leave your stomach sour, the word "buffered" on a bottle starts to matter.

Ester-C day-cycle illustration: the same city at night

How to Read a Vitamin C Supplement Facts Label, Line by Line

Turn a bottle of Ester-C around and the black-ruled box on the back answers most questions before the first tablet.

Sources

The articles are general information, not medical advice.

Vitamin C: Fact Sheet for Health Professionals, NIH Office of Dietary Supplements. Read October 25, 2026.
Vitamin C: Fact Sheet for Consumers, NIH Office of Dietary Supplements. Read October 25, 2026.
Daily Value on the Nutrition and Supplement Facts Labels, U.S. Food and Drug Administration. Read October 25, 2026.
Safety and tolerance of Ester-C compared with regular ascorbic acid (Gruenwald et al., Advances in Therapy, 2006), PubMed, National Library of Medicine. Read October 25, 2026.
Determination of plasma and leukocyte vitamin C concentrations in a randomized, double-blind, placebo-controlled trial with Ester-C (Mitmesser et al., SpringerPlus, 2016), PubMed Central, National Library of Medicine. Read October 25, 2026.
Calcium: Fact Sheet for Consumers, NIH Office of Dietary Supplements. Read October 25, 2026.
Dietary Supplement Labeling Guide: Chapter IV, Nutrition Labeling, U.S. Food and Drug Administration. Read October 25, 2026.
Dietary Supplement Labeling Guide: Chapter VI, Claims, U.S. Food and Drug Administration. Read October 25, 2026.
Structure/Function Claims, U.S. Food and Drug Administration. Read October 25, 2026.