Ingredient
Vitamin C
Research dose
200–1000 mg/day
Evidence: Moderate Trials gave vitamin c daily, for weeks: what counts is the amount you take in a day.
Blood levels leave the steep part of the dose curve at 200 mg a day and are saturated at 1,000 mg; above about 400 mg a day the study saw no evident added value, and single doses of 500 mg or more are absorbed less. The RDA, set to prevent deficiency, is 90 mg for men and 75 mg for women. The US upper limit is 2 g a day; above it, stomach upset is more likely.
Upper reference: 2 g per serving. One serving at or above it is marked “too much”.
Sources
Frei B, Birlouez-Aragon I, Lykkesfeldt J. Authors' perspective: What is the optimum intake of vitamin C in humans? Crit Rev Food Sci Nutr. 2012;52(9):815-829.
Supports the research dose. Where: Abstract: "200 mg per day is the optimum dietary intake of vitamin C for the majority of the adult population". Read the source, checked 9 Oct 2026.
Gonzalez DE, Dickerson BL, Roberts BM, et al. International Society of Sports Nutrition position stand: effects of dietary antioxidants on exercise and sports performance. J Int Soc Sports Nutr. 2026;23(1):2629828.
Supports the research dose. Where: Table 2, Vitamins E & C: "Vit C: 1000 mg/day". Read the source, checked 9 Oct 2026.
Levine M, Conry-Cantilena C, Wang Y, et al. Vitamin C pharmacokinetics in healthy volunteers: evidence for a recommended dietary allowance. Proc Natl Acad Sci U S A. 1996;93(8):3704-3709.
Supports the research dose. Where: Abstract: "the first dose beyond the sigmoid portion of the curve was 200 mg daily, and complete plasma saturation occurred at 1000 mg daily"; "vitamin C daily doses above 400 mg have no evident value". Read the source, checked 9 Oct 2026.
Lykkesfeldt J, Carr AC. Vitamin C. Adv Nutr. 2024;15(1):100155.
Supports the upper reference. Where: Section "Toxicity": "The current tolerable upper intake level was set to 2 g/d by the National Academy of Medicine in 2000"; section "Dietary recommendation": RDA "75 and 90 mg/d for females and males". Read the source, checked 9 Oct 2026.
Vitamin C supplements we've checked
21 vitamin C supplements, each judged on how much a day its label's own directions give. See them all, ranked.
In the pre-workouts we've checked
| Product | Per scoop | Verdict |
|---|---|---|
| NutraBio PRE | 150 mg | Not graded |
| BSN N.O.-Xplode Vaso | 200 mg | Not graded |
| PEScience High Volume | 125 mg | Not graded |
| Bare Performance Nutrition Flight | 500 mg | Not graded |
| Ghost Legend All Out | 250 mg | Not graded |
| Jocko Fuel Pre-Workout | 90 mg | Not graded |
| ProSupps Mr. Hyde Max Pump | 60 mg | Not graded |
| ANS Performance Ritual | 105 mg | Not graded |
| Bloom Nutrition High Energy Pre-Workout | 100 mg | Not graded |
| Cellucor C4 Ripped | 250 mg | Not graded |
| EHP Labs OxyShred | 173 mg | Not graded |
| Jocko Fuel Go Pre-Workout | 500 mg | Not graded |
| MusclePharm Assault | 300 mg | Not graded |
| Naked Nutrition Naked Energy | 167 mg | Not graded |
| Old School Labs Vintage Blast | 250 mg | Not graded |
| Six Star Pre-Workout Explosion | 250 mg | Not graded |