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Vitamin C
Clinical dose: 500-2,000mg daily for therapeutic or immune support, split into divided doses
At a Glance
Vitamin C (ascorbic acid) is one of the most thoroughly studied dietary supplements, with a robust evidence base from large meta-analyses and systematic reviews. It is an essential nutrient that humans cannot synthesize, making dietary or supplemental intake necessary. The Cochrane systematic review by Hemila and Chalker (2013, PMID: 23440782) is the definitive analysis, pooling data from 29 trials with over 11,000 participants. Our top pick is Extra Strength Vitamin C 1000 mg Tablets (Grade: A, $0.15/day).
Quick Picks
What Is Vitamin C?
Vitamin C (ascorbic acid) is one of the most thoroughly studied dietary supplements, with a robust evidence base from large meta-analyses and systematic reviews. It is an essential nutrient that humans cannot synthesize, making dietary or supplemental intake necessary. The Cochrane systematic review by Hemila and Chalker (2013, PMID: 23440782) is the definitive analysis, pooling data from 29 trials with over 11,000 participants. The key findings are that regular Vitamin C supplementation (1-2g/day) does not reliably prevent colds in the general population, but it does reduce the duration of cold symptoms by approximately 8% in adults and 14% in children. Importantly, in individuals under heavy physical stress - marathon runners, soldiers, and skiers - prophylactic Vitamin C supplementation reduced cold incidence by roughly 50% across 5 trials with 598 participants. This is a strong and consistent finding. For skin health and collagen synthesis, a comprehensive review by Pullar et al. (2017, PMID: 28805671) established Vitamin C as a critical cofactor for the enzymes prolyl hydroxylase and lysyl hydroxylase, which are essential for stabilizing the collagen molecule. This role in collagen synthesis supports wound healing and may help reduce signs of skin aging, though the evidence for supplemental (as opposed to dietary) Vitamin C specifically improving skin appearance is moderate. Vitamin C also has strong evidence for enhancing non-heme iron absorption. Hallberg et al. (1989, PMID: 2507689) demonstrated that taking as little as 50-100mg of Vitamin C with a meal significantly boosts absorption of plant-based iron sources. This makes Vitamin C supplementation particularly valuable for vegetarians, vegans, and individuals with iron deficiency who rely on non-heme iron sources. A practical note on bioavailability: GI absorption of Vitamin C decreases sharply above 1,000mg per single dose. Divided dosing (e.g., 500mg twice daily) is more efficient than taking 1,000mg at once. The upper tolerable limit is 2,000mg/day, above which GI distress becomes common.
Does It Work? The Evidence
| Claimed Benefit | Evidence Level | Key Studies | Our Verdict |
|---|---|---|---|
| Reduces duration and severity of the common cold | Strong | Hemila & Chalker 2013 Cochrane review (29 trials, n=11,306): regular supplementation at 1-2g/day reduces cold duration by 8% in adults and 14% in children | Works |
| Halves cold incidence in individuals under heavy physical stress | Strong | Hemila & Chalker 2013 Cochrane review (5 trials, n=598): ~50% reduction in cold incidence in marathon runners, soldiers, and skiers | Works |
| Supports collagen synthesis and skin health | Moderate | Pullar et al. 2017 review (PMID: 28805671): Vitamin C is a critical cofactor for prolyl and lysyl hydroxylase, essential for collagen stabilization | Promising |
| Increases non-heme iron absorption | Strong | Hallberg et al. 1989 (PMID: 2507689): 50-100mg Vitamin C with a meal significantly boosts plant-based iron absorption | Works |
How to Choose: Forms, Doses & What Matters
Clinical dose: 500-2,000mg daily for therapeutic or immune support, split into divided doses
Best forms: Ascorbic acid (highly bioavailable, standard form in most trials), Sodium ascorbate (buffered, better tolerated by sensitive stomachs), Liposomal Vitamin C (slightly higher peak plasma levels, rarely justifies price premium), Calcium ascorbate / Ester-C (includes metabolites, mixed evidence of superior bioavailability)
Take in divided doses (e.g., 500mg twice daily) to maximize absorption, as GI absorption decreases sharply above 1,000mg per single dose. Standard ascorbic acid can be taken with or without food, though taking with meals reduces stomach irritation. Buffered forms (sodium ascorbate, calcium ascorbate) are gentler on the stomach for sensitive individuals. For iron absorption, take alongside an iron-rich meal or iron supplement.
The Scorecard: 10 Products Compared
Extra Strength Vitamin C 1000 mg Tablets
Nature MadeUSP Verified ascorbic acid at an excellent price - the benchmark for quality-verified Vitamin C
Full clinical dose of ascorbic acid matching trial specifications
USP Verified for purity and potency - the gold standard in third-party verification
$0.15/day at 1,000mg - excellent value for a USP Verified product
Full label disclosure with exact form and amount specified
Prices checked 2026-03-31. Cost shown is per clinically effective daily dose, not per pill.
Sodium Ascorbate, Crystalline Powder, 16 oz
NutriBiotic
Outstanding bulk value in powder format - buffered sodium ascorbate is easy on the GI tract at high doses, requires manual measuring
Standard buffered Vitamin C (sodium ascorbate) at a fully customizable dose
GMP certified but no independent third-party purity certification
$0.07/day at 1,000mg - incredibly high value due to bulk powder format
Simple, single-ingredient formula with full dose disclosure
Prices checked 2026-03-31. Cost shown is per clinically effective daily dose, not per pill.
C-1000, 250 Tablets
NOW FoodsOutstanding price per dose from a reputable GMP-certified brand with added bioflavonoids from rose hips
Full clinical dose of ascorbic acid with rose hips
GMP certified facility but no independent third-party purity certification
$0.08/day at 1,000mg - outstanding value
Full disclosure of form, amount, and added rose hips
Prices checked 2026-03-31. Cost shown is per clinically effective daily dose, not per pill.
Vitamin C with Rose Hips, 1000 mg, 500 Count
Spring Valley
Absolute lowest cost per dose at $0.03/day but lacks any verifiable third-party testing or GMP documentation
Full clinical dose of standard ascorbic acid
No verifiable third-party testing or explicit GMP facility documentation
$0.03/day - the lowest cost per dose of any product tested
Full label disclosure with form and amount clearly specified
Prices checked 2026-03-31. Cost shown is per clinically effective daily dose, not per pill.
Ester-C, Maximum Strength, 1,000 mg, 120 Tablets
Nature's Bounty
Buffered with calcium making it non-acidic and well-tolerated by sensitive stomachs, with naturally occurring metabolites for potentially longer retention
Full clinical dose using calcium ascorbate with naturally occurring metabolites
GMP certified but no independent third-party purity certification
$0.14/day - excellent value for a branded form of Vitamin C
Full disclosure of form and amount with branded Ester-C identification
Prices checked 2026-03-31. Cost shown is per clinically effective daily dose, not per pill.
Vitamin C with Flavonoids, 90 Capsules
ThornePremium practitioner-grade quality with added citrus bioflavonoids, but requires 2 capsules for the clinical 1,000mg dose
Uses standard ascorbic acid with citrus bioflavonoids to mimic the natural form found in whole foods
Trusted practitioner brand with TGA certified facility and high manufacturing standards
$0.51/day at 1,000mg (2 capsules) - premium pricing for a practitioner-grade brand
Full label disclosure with clear ingredient identification
Prices checked 2026-03-31. Cost shown is per clinically effective daily dose, not per pill.
Emergen-C 1000mg Vitamin C Powder, 30 ct
Emergen-C
Convenient single-use packets with electrolytes and B vitamins, but you pay a significant premium for the format over standard tablets
Full clinical dose of ascorbic acid with added B vitamins and electrolytes
GMP certified but no independent third-party purity certification
$0.47/day - significantly more expensive than bottled tablets for the same amount of Vitamin C
Full disclosure of all ingredients and amounts
Prices checked 2026-03-31. Cost shown is per clinically effective daily dose, not per pill.
Lypo-Spheric Liposomal Vitamin C 1000mg
LivOn Labs
Liposomal delivery may slightly increase peak plasma levels, but rarely justifies the 1000%+ price markup over standard ascorbic acid
Full clinical dose of Vitamin C in a liposomal delivery system
GMP certified but no independent third-party purity certification
$1.53/day - extremely overpriced compared to the marginal bioavailability benefit of liposomal format
Full disclosure of form and amount - buffered sodium ascorbate in phospholipid encapsulation
Prices checked 2026-03-31. Cost shown is per clinically effective daily dose, not per pill.
Vitamin Code RAW Vitamin C, 120 Capsules
Garden of LifeContains organic fruit/vegetable blends and probiotics, but requires 4 capsules for a 1,000mg therapeutic dose making it extremely expensive
Provides Vitamin C from whole-food cultured source (Saccharomyces cerevisiae)
GMP certified but no independent third-party purity certification
$0.89/day at 1,000mg (4 capsules) - very expensive for Vitamin C supplementation
Relies on proprietary blends for fruit/vegetable base and probiotic components
Prices checked 2026-03-31. Cost shown is per clinically effective daily dose, not per pill.
1000mg Vitamin C Immune Support Chewable Tablets
Airborne
Overpriced with proprietary herbal blend, low serving count, and no quality certifications - pure marketing premium
Provides 1,000mg of Vitamin C per serving (4 tablets)
No verified GMP certification, no independent third-party testing
$1.00/day - very expensive due to low serving count (8 servings per bottle)
Uses a proprietary herbal blend hiding exact amounts of echinacea and other ingredients
Prices checked 2026-03-31. Cost shown is per clinically effective daily dose, not per pill.
Full Comparison
| Category | Extra Strength Vitamin C 1000 mg Tablets Nature Made | Sodium Ascorbate, Crystalline Powder, 16 oz NutriBiotic | C-1000, 250 Tablets NOW Foods | Vitamin C with Rose Hips, 1000 mg, 500 Count Spring Valley | Ester-C, Maximum Strength, 1,000 mg, 120 Tablets Nature's Bounty | Vitamin C with Flavonoids, 90 Capsules Thorne | Emergen-C 1000mg Vitamin C Powder, 30 ct Emergen-C | Lypo-Spheric Liposomal Vitamin C 1000mg LivOn Labs | Vitamin Code RAW Vitamin C, 120 Capsules Garden of Life | 1000mg Vitamin C Immune Support Chewable Tablets Airborne |
|---|---|---|---|---|---|---|---|---|---|---|
| Overall | A | A- | A- | B+ | B+ | B+ | B- | B- | C | C- |
| Evidence | A | A | A | A | A | A | A | A | A | A |
| Quality & Purity | A | C | C | D | C | B | C | C | C | D |
| Value | A | A | A | A | B | C | D | F | D | F |
| Transparency | A | A | A | A | A | A | A | A | D | D |
| Cost/Day | $0.15 | $0.07 | $0.08 | $0.03Winner | $0.14 | $0.51 | $0.47 | $1.53 | $0.89 | $1.00 |
| Dose/Serving | 1000mg | 850mg | 1000mg | 1000mg | 1000mg | 500mg | 1000mg | 1000mg | 500mg | 1000mg |
| Form | Ascorbic Acid | Sodium Ascorbate | Ascorbic Acid with Rose Hips | Ascorbic Acid | Calcium Ascorbate (Ester-C) | Ascorbic Acid | Ascorbic Acid | Liposomal Sodium Ascorbate | Vitamin C (from Saccharomyces cerevisiae culture) | Ascorbic Acid and Sodium Ascorbate |
| Third-Party Tested | ✓ Yes | No | No | No | No | ✓ Yes | No | No | No | No |
| Proprietary Blend | No | No | No | No | No | No | No | No | Yes | Yes |
Who Should Take Vitamin C?
Individuals under extreme physical stress or heavy athletic training, where the evidence for cold prevention is strongest. Smokers, who have increased oxidative stress and require an additional 35mg/day above the RDA. Those looking to modestly reduce the duration of cold symptoms during cold and flu season. Vegans and vegetarians taking iron supplements or relying on non-heme iron sources, as Vitamin C dramatically improves iron absorption.
Who Should Avoid It?
Individuals with a history of calcium oxalate kidney stones, as high doses of Vitamin C can increase urinary oxalate excretion. Patients with hemochromatosis or iron-overload disorders, as Vitamin C enhances iron absorption and could worsen iron overload. Individuals with G6PD deficiency face a rare risk of hemolysis at extremely high IV doses, though standard oral supplementation is generally safe.
Side Effects & Safety
The most common side effects are gastrointestinal - diarrhea, nausea, and cramping - typically occurring at doses exceeding 2,000mg/day. These are dose-dependent and resolve by reducing intake. Chronic high-dose supplementation may increase the risk of kidney stones in susceptible individuals through increased oxalate excretion. Buffered forms (sodium ascorbate, calcium ascorbate) are better tolerated than plain ascorbic acid for those with sensitive stomachs.
Frequently Asked Questions
Does Vitamin C prevent colds?
In the general population, regular Vitamin C supplementation does not reliably prevent colds. However, it consistently reduces the duration of colds by about 8% in adults (roughly half a day) and 14% in children. The exception is people under heavy physical stress (marathon runners, soldiers, skiers), where Vitamin C reduces cold incidence by approximately 50%.
Is liposomal Vitamin C worth the extra cost?
Rarely. Liposomal Vitamin C achieves slightly higher peak plasma levels than standard ascorbic acid, but the difference is modest and unlikely to produce meaningfully different health outcomes. Standard ascorbic acid costs $0.03-0.15 per 1,000mg dose, while liposomal versions cost $1.00-1.50+. The 10-50x price premium is not justified by the marginal bioavailability improvement.
What is the best form of Vitamin C?
Plain ascorbic acid is the standard form used in most clinical trials and is the most cost-effective. Sodium ascorbate is a buffered form that is gentler on the stomach with similar bioavailability. Calcium ascorbate (Ester-C) includes vitamin C metabolites but evidence of superior absorption is mixed. For most people, plain ascorbic acid is the best value.
Should I take more Vitamin C when I feel a cold coming on?
The evidence for therapeutic dosing (taking extra Vitamin C after cold symptoms start) is weaker than for prophylactic use. Some studies suggest 6-8g/day at cold onset may modestly reduce duration, but the evidence is inconsistent. Regular daily supplementation (1-2g/day) before getting sick is more reliably effective.
Can I get enough Vitamin C from food?
Easily, if you eat fruits and vegetables regularly. One orange provides about 70mg, a cup of strawberries about 90mg, and a red bell pepper about 190mg. The RDA is only 75-90mg, which prevents deficiency. However, the therapeutic doses used in clinical trials (500-2,000mg) are difficult to reach through diet alone.
Is it true that Vitamin C is destroyed by cooking?
Partially. Vitamin C is heat-sensitive and water-soluble, so boiling vegetables in water can reduce their Vitamin C content by 50% or more. Steaming, microwaving, or eating raw preserves more. This is why supplementation can be useful even for people who eat produce regularly, if they cook most of their vegetables.
Why is there such a huge price range for Vitamin C supplements?
The active ingredient (ascorbic acid) is one of the cheapest supplements to manufacture. Price differences come from branding, delivery format (tablets vs packets vs liposomal gel), added ingredients, third-party testing, and marketing. A USP Verified ascorbic acid tablet at $0.03-0.15 per dose delivers the same Vitamin C as a $1.50 liposomal packet.
Sources
- Hemila H, Chalker E. Vitamin C for preventing and treating the common cold. Cochrane Database Syst Rev. 2013;(1):CD000980.
- Pullar JM, Carr AC, Vissers MCM. The Roles of Vitamin C in Skin Health. Nutrients. 2017;9(8):866.
- Hallberg L, et al. The role of vitamin C in iron absorption. Int J Vitam Nutr Res Suppl. 1989;30:103-8.
FDA Disclaimer: These statements have not been evaluated by the Food and Drug Administration. The products discussed on this page are not intended to diagnose, treat, cure, or prevent any disease. Always consult with a qualified healthcare professional before starting any supplement regimen.