Twinlab · Vitamin C · Capsules
Is Twinlab C-1000 Caps underdosed?
Verdict
1 g a dayas the label directs · studies use 200–1,000 mg a day · RDA 90 mg · upper limit 2,000 mg
Effective doseTaken as the label directs (1 serving a day, 1 g each), it gives 1 g a day. Studies of vitamin C supplements use 200–1,000 mg a day; the RDA is 90 mg for men and 75 mg for women, and the US upper limit is 2,000 mg a day. In the same studies, single doses of 500 mg or more were absorbed less than smaller ones.
One capsule gives 1 g, enough on its own for the low end of what studies use (200 mg); it ranks 13th of 21 vitamin C supplements here by dose.
1 capsule a day reaches 200 mg.
What the label says
- Vitamin C per serving
- 1 g in 1 capsule
- Servings a day
- 1 serving a day
- Vitamin C a day, as directed
- 1 g
- Reference
- studies use 200–1,000 mg a day · RDA 90 mg · upper limit 2,000 mg Evidence: Moderate
Directions: Take one capsule one ore more times daily.
More about vitamin c: forms, timing and the studies behind the dose.
Same category, compared
All 21 vitamin C supplements we checked, ranked by dose (commission never changes the order). Studies use 200–1,000 mg a day · RDA 90 mg · upper limit 2,000 mg; servings counted to 200 mg.
| Product | Per serving | Servings to reach it | Form |
|---|---|---|---|
| Airborne Citrus Chewable Tablets | 1 g | 1 or less | Tablets · ascorbic acid and sodium ascorbate |
| Airborne Original Effervescent Tablets | 1 g | 1 or less | Tablets · ascorbic acid |
| Beekeeper's Naturals Propolis + Vitamin C Liposomal | 1 g | 1 or less | Liquids · ascorbic acid & sodium ascorbate |
| Dr. Mercola Liposomal Vitamin C 1,000 mg | 1 g | 1 or less | Capsules · ascorbic acid |
| Emergen-C 1,000 mg Vitamin C | 1 g | 1 or less | Powders · ascorbic acid, zinc ascorbate |
| MegaFood Liposomal Vitamin C 1000 mg | 1 g | 1 or less | Capsules · ascorbic acid |
| Member's Mark Vitamin C 1000 mg | 1 g | 1 or less | Tablets · ascorbic acid |
| NOW Foods C-1000 | 1 g | 1 or less | Tablets · ascorbic acid |
| NutraBio Vitamin C 1000 mg | 1 g | 1 or less | Capsules · ascorbic acid |
| Puritan's Pride C-1000 mg | 1 g | 1 or less | Tablets · ascorbic acid |
| Puritan's Pride Ester-C | 1 g | 1 or less | Capsules · ester-c |
| Solaray Buffered Super Bio Vitamin C 1000 mg | 1 g | 1 or less | Capsules · acerola cherry, ascorbic acid, rose hip |
| Twinlab C-1000 Caps (this product) | 1 g | 1 or less | Capsules · ascorbic acid |
| Airborne Original Gummies | 750 mg | 1 or less | Gummies · ascorbic acid, sodium ascorbate |
| Pure Encapsulations Ester-C & Flavonoids | 619 mg | 1 or less | Capsules · ester-c calcium ascorbate |
| Amazon Elements Whole Food Vitamin C 500 mg | 500 mg | 1 or less | Capsules · acerola extract, ascorbic acid |
| Bluebonnet Vitamin C 500 mg | 500 mg | 1 or less | Capsules · l-ascorbic acid |
| Garden of Life Vitamin Code Raw Vitamin C | 500 mg | 1 or less | Capsules · saccharomyces cerevisiae |
| Nature Made Vitamin C 500 mg | 500 mg | 1 or less | Tablets |
| Source Naturals C-1000 | 1 g | 1 or less | Tablets · ascorbic acid |
| Sports Research Vitamin C 1000 mg | 1 g | 1 or less | Capsules · ascorbic acid |
Where the reference doses come from
- Vitamin C, 200–1000 mg/day: Frei et al., 2012; Gonzalez et al., 2026; Levine et al., 1996.
- Label data: National Institutes of Health, Office of Dietary Supplements. Dietary Supplement Label Database, 2026. https://dsld.od.nih.gov/. Label 268464, including its servings a day.
For a supplement taken every day we judge the most the label's directions give in a day, and show the least. Read the full methodology or the corrections log.