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Quercetin Complex

Natrol
4.7
★ ★ ★ ★ ★
(1283 ratings)
Flavonoid 66 mg
Vitamin C 1000 mg
Product Image
Score80
A meaningful quercetin dose with vitamin C is well targeted, though absorption support, bioflavonoid detail, and serving count are limited.
How scoring works
Quantity:50 Capsule(s) • (25 servings)
Goals:
Immunity
General Health
Anti-Inflammatory Support
Skin Health
Vision Support

Score 80

A meaningful quercetin dose with vitamin C is well targeted, though absorption support, bioflavonoid detail, and serving count are limited.
How scoring works
$11.10($0.44 per serving)
Amazon
$ 0.00
iHerb
$ 11.10
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Analysis

Quercetin at 500 mg is the central ingredient and is paired with 1,000 mg of vitamin C plus a citrus bioflavonoid complex. The focused combination is more purposeful than a lightly dosed multi-ingredient antioxidant blend.

No enhanced-absorption form or delivery aid is identified for quercetin, so bioavailability may be less predictable than with specialized formulations. The citrus bioflavonoid complex is also not standardized or broken down.

A two-capsule serving delivers substantial amounts, but the bottle provides only 25 servings. It fits buyers who want a direct quercetin formula and tolerate higher-dose vitamin C, rather than those seeking a low-dose maintenance product.

Who is it for
  • Adults seeking a substantial quercetin dose
  • People who want vitamin C alongside a flavonoid
Best for
  • Focused quercetin supplementation
  • Combined flavonoid and vitamin C support

Pros

  • Provides 500 mg of quercetin
  • Includes 1,000 mg of vitamin C
  • Focused ingredient combination
  • Clearly listed active amounts

Cons

  • No stated quercetin absorption aid
  • Bioflavonoid complex is not standardized
  • Only 25 servings
  • Requires two capsules per serving

Warnings

  • Vitamin C at 1,000 mg may cause stomach upset or loose stools in sensitive users.
  • Quercetin may interact with cyclosporine and some drugs handled by CYP3A4 or P-glycoprotein; users of these medicines should ask their prescriber before use.

Nutrient quality

88 Highest impact

Vitamin C and quercetin both reach substantial amounts in a coherent formula. Missing quercetin form detail and the high vitamin C load are the main limitations.

Ingredient transparency

82 Highest impact

All three active amounts are stated and no proprietary blend appears. Bioflavonoid composition, excipients, and complete use directions are not supplied.

Customer satisfaction

69 High impact

The average rating is strong and the large evidence base makes it more dependable. No specific feedback is supplied to judge repeated complaints or alignment with the intended use.

Value for money

77 High impact

Strong active dosing and a focused formula help justify some of the cost. The short supply makes serving value less competitive within the category.

Report analysis

Goals

Immunity
Immunity
Impact
Highest effect
A- Goal FitA+ Strength of SupportB CoverageA- Formula Quality
Vitamin C · 1000 mg

Vitamin C and quercetin provide direct antioxidant and immune-cell support in substantial amounts. Clear disclosure makes the main actives easy to assess.

Evidence is strongest for vitamin C, while quercetin has less consistent human evidence for respiratory infections. The streamlined flavonoid combination is more focused than a broad proprietary immune blend.

Study evidence
Vitamin C Supportive 53 studies
General Health
General Health
Impact
Highest effect
A- Goal FitA- Strength of SupportB CoverageA Formula Quality
Vitamin C · 1000 mg

Vitamin C provides substantial antioxidant, immune, and collagen support, while quercetin and citrus bioflavonoids broaden the antioxidant profile. The combination is relevant to general health but remains more focused than a comprehensive foundational formula.

All active amounts are disclosed, though plain ascorbic acid is unbuffered and quercetin has no stated absorption enhancer. The vitamin C amount may cause stomach upset or loose stools in sensitive users.

Study evidence
Vitamin C Supportive 56 studies
Anti-Inflammatory Support
Anti-Inflammatory Support
Impact
Highest effect
B+ Goal FitA- Strength of SupportB CoverageA Formula Quality
Vitamin C · 1000 mg

Quercetin directly affects inflammatory signaling and pairs logically with vitamin C and citrus bioflavonoids for antioxidant support. The 500 mg quercetin and 1,000 mg vitamin C amounts are substantial rather than decorative.

Generic quercetin lacks a phytosome or other absorption technology, which may limit effective exposure. The high vitamin C amount may cause nausea or diarrhea, and people prone to calcium-oxalate kidney stones may increase urinary oxalate with regular use.

Study evidence
Vitamin C Supportive 50 studies
Skin Health
Skin Health
Impact
Highest effect
A- Goal FitA- Strength of SupportC+ CoverageA Formula Quality
Vitamin C · 1000 mg

Vitamin C directly supports collagen synthesis and antioxidant defense in skin. Vitamin C has established human and mechanistic evidence for collagen formation and antioxidant protection.

The clearly disclosed 1,000 mg vitamin C amount provides more than enough collagen-synthesis cofactor for most users. Vitamin C covers collagen synthesis and antioxidant defense but not direct hydration or barrier-lipid support.

Study evidence
Vitamin C Supportive 53 studies
Vision Support
Vision Support
Impact
High effect
C Goal FitB Strength of SupportD CoverageB Formula Quality
Vitamin C · 1000 mg

Vitamin C provides meaningful antioxidant support for the lens and other ocular tissues. The disclosed amount is substantial enough to contribute rather than merely decorate the label.

Its strongest vision evidence comes from use within broader nutrient combinations. The formula does not supply macular carotenoids, retinal omega-3s, or balanced zinc and copper.

Study evidence
Vitamin C Disputed 24 studies

Ingredients

IngredientAmount per serving
Vitamin C (Ascorbic Acid)
 1000 mg
Quercetin
500 mg
Citrus Bioflavonoid Complex
66 mg
Adults 18–50 Dairy Free
Report overview
Flavonoid · 66 mg OverallScore86
B- Active Ingredient Quality & BioavailabilityA Dose, Safety & Label TransparencyA+ Value

The formula clearly supplies 500 mg of quercetin plus 66 mg of citrus bioflavonoids. A standard capsule offers no specialized help for quercetin's limited solubility. Strong dose disclosure and a low cost per active amount support excellent practical value.

View ingredientView products
Vitamin C (Ascorbic Acid) · 1000 mg OverallScore58
F Active Ingredient Quality & BioavailabilityA Dose, Safety & Label TransparencyD+ Value

The 1,000 mg vitamin C serving is well targeted and accompanies substantial quercetin. Plain ascorbic acid offers no buffering or enhanced delivery, while the complete other-ingredients panel is unavailable. Vitamin C cost efficiency is only moderate.

View ingredientView products
Loading alternative details
89 Performance

C-500 Calcium Ascorbate-C

NOW
<p>Buffered calcium ascorbate provides a practical vitamin C amount with clear calcium disclosure and a small citrus bioflavonoid addition. The buffered form offers a simpler and more clearly characterized vitamin C option, but it is not a substitute for a substantial quercetin dose.</p>
88 Performance

Sodium Ascorbate Capsules

NutriBiotic Immunity
<p>Buffered sodium ascorbate supplies a useful vitamin C amount with its sodium contribution clearly disclosed. The buffered form and transparent sodium contribution improve label clarity, though the narrower formula omits quercetin.</p>
88 Performance

Buffered Gold C

California Gold Nutrition
<p>Buffered sodium ascorbate provides a substantial vitamin C serving in a simple, fully quantified active profile. The buffered, simple active profile is easier to assess and may be gentler, but it gives up the original’s flavonoid depth.</p>
82 Budget

Metabolic C 500 mg

Source Naturals
<p>Vitamin C and citrus bioflavonoids preserve the original collection match in a focused antioxidant formula. It keeps vitamin C and citrus bioflavonoids at a much lower serving cost, though it does not replace the original’s quercetin.</p>
82 Budget

Vitamin C with Flavonoids

Thorne
<p>Vitamin C and citrus bioflavonoids preserve the same two collection themes in a simple formula. It preserves the same two collections at a lower serving cost, but the original remains stronger for quercetin-specific use.</p>
82 Budget

Meta-C 1000 mg Tablets

NutriBiotic Immunity
<p>The Meta-C complex supplies vitamin C with calcium, named metabolites, and spirulina in a potentially gentler format. Its lower serving cost and potentially gentler vitamin C format improve economy, though flavonoid coverage is lost.</p>
85 Value

C-500 With Rose Hips

NOW
<p>A focused ascorbic acid serving with rose hips covers core vitamin C needs without an elaborate blend. Its very low serving cost makes it a strong value for core vitamin C needs, though it is much narrower than the original.</p>
85 Value

Gold C Vitamin C 1000 mg

California Gold Nutrition
<p>A simple ascorbic acid serving provides substantial vitamin C without active padding. Its substantial vitamin C amount and low serving cost improve value, provided quercetin is not the main reason for use.</p>
84 Value

Ester-C 500 mg With Citrus Bioflavoinds

American Health
<p>Buffered calcium ascorbate combines a substantial vitamin C serving with a sizeable citrus bioflavonoid complex. Buffered vitamin C plus a sizeable citrus bioflavonoid complex provides useful depth at a much lower serving cost, though quercetin is absent.</p>
Report alternatives

Sources

Published studies used for the product analysis and the top-ranked studies for each ingredient and goal.

  1. Vitamin C intake and multiple health outcomes: an umbrella review of systematic reviews and meta-analyses.
    Xu K; Peng R; Zou Y; Jiang X; Sun Q; Song C · International journal of food sciences and nutrition · 2022
    Meta-analysis76 studies pooledGeneral Health forVitamin C
  2. Associations of Serum Biomarkers of Fruit and Vegetable Intake With the Risk of Cause-Specific Mortality and All-Cause Mortality: A National Prospective Cohort Study.
    Pu L; Zhang R; Wang X; Zhao T; Sun H; Han L · Frontiers in nutrition · 2022
    Cohort study12,530 participantsGeneral Health forVitamin C
  3. Mortality in randomized trials of antioxidant supplements for primary and secondary prevention: systematic review and meta-analysis.
    Bjelakovic G; Nikolova D; Gluud LL; Simonetti RG; Gluud C · JAMA · 2007
    Meta-analysis232,606 participants68 studies pooledGeneral Health forVitamin C
  4. Supplemental Vitamins and Minerals for Cardiovascular Disease Prevention and Treatment: JACC Focus Seminar.
    Jenkins DJA; Spence JD; Giovannucci EL; Kim YI; Josse RG; Vieth R; Sahye-Pudaruth S; Paquette M; Patel D; Blanco Mejia S; Viguiliouk E; Nishi SK; Kavanagh M; Tsirakis T; Kendall CWC; Pichika SC; Sievenpiper JL · Journal of the American College of Cardiology · 2021
    Meta-analysisGeneral Health forVitamin C
  5. Efficacy of Vitamin C as Glucocorticoid Substitute for Reducing Pain and Inflammation After Total Hip Arthroplasty: A Randomized Controlled Trial.
    Jiang W; Xu H; Jiang X; Zhan Y; Ju Y; Xie J; Huang Z; Huang Q; Pei F · The Journal of bone and joint surgery. American volume · 2025
    Randomized trial107 participantsAnti-Inflammatory Support forVitamin C
  6. The Impact of Vitamin C on Analgesic, Anti-inflammatory, and Hemostatic Outcomes After Total Hip and Knee Arthroplasty: A Systematic Review and Meta-Analysis.
    Moftakhari Hajimirzaei S; Bagherzadeh Cham M; Dolikhani M; Tabatabaee SM; Ebrahimpour A · The archives of bone and joint surgery · 2026
    Meta-analysis1,162 participants10 studies pooledAnti-Inflammatory Support forVitamin C
  7. The impact of vitamin C supplementation on the perioperative outcomes after total hip and knee arthroplasty: a systematic review and meta-analysis.
    Liu X; Guo J; Li Y; Yang Y; Liu M; Gao Q; Yang Y; Wu X; Yue C · BMC musculoskeletal disorders · 2026
    Meta-analysis852 participants8 studies pooledAnti-Inflammatory Support forVitamin C
  8. Therapeutic Impact of Ascorbic Acid on Oral and Periodontal Tissues: A Systematic Literature Review.
    Ruzijevaite G; Acaite E; Jagelaviciene E · Medicina (Kaunas, Lithuania) · 2025
    Systematic review811 participants17 studies pooledAnti-Inflammatory Support forVitamin C
  9. Oral vitamin C administration reduces early recurrence rates after electrical cardioversion of persistent atrial fibrillation and attenuates associated inflammation.
    Korantzopoulos P; Kolettis TM; Kountouris E; Dimitroula V; Karanikis P; Pappa E; Siogas K; Goudevenos JA · International journal of cardiology · 2005
    Randomized trial44 participantsAnti-Inflammatory Support forVitamin C
  10. Dietary intake and blood concentrations of antioxidants and the risk of cardiovascular disease, total cancer, and all-cause mortality: a systematic review and dose-response meta-analysis of prospective studies.
    Aune D; Keum N; Giovannucci E; Fadnes LT; Boffetta P; Greenwood DC; Tonstad S; Vatten LJ; Riboli E; Norat T · The American journal of clinical nutrition · 2019
    Meta-analysis69 studies pooledGeneral Health forVitamin C
  11. Scientific Opinion on the substantiation of a health claim related to vitamin C and increasing non haem iron absorption pursuant to Article 14 of Regulation (EC) No 1924/2006.
    EFSA Panel on Dietetic Products, Nutrition and Allergies (NDA) · EFSA journal. European Food Safety Authority · 2026
    Guideline / consensusGeneral Health forVitamin C
  12. Vitamin C Depletion and All-Cause Mortality in Renal Transplant Recipients.
    Sotomayor CG; Eisenga MF; Gomes Neto AW; Ozyilmaz A; Gans ROB; Jong WHA; Zelle DM; Berger SP; Gaillard CAJM; Navis GJ; Bakker SJ · Nutrients · 2018
    Cohort study598 participantsGeneral Health forVitamin C
  13. Relation between plasma ascorbic acid and mortality in men and women in EPIC-Norfolk prospective study: a prospective population study. European Prospective Investigation into Cancer and Nutrition.
    Khaw KT; Bingham S; Welch A; Luben R; Wareham N; Oakes S; Day N · Lancet (London, England) · 2001
    Cohort study19,496 participantsGeneral Health forVitamin C
  14. Vitamin C and contribution to the normal function of the immune system: evaluation of a health claim pursuant to Article 14 of Regulation (EC) No 1924/2006.
    EFSA Panel on Dietetic Products, Nutrition and Allergies (NDA) · EFSA journal. European Food Safety Authority · 2026
    Guideline / consensusImmunity forVitamin C
  15. Therapeutic effects of high-dose vitamin C supplementation in patients with COVID-19: a meta-analysis.
    Sun L; Zhao JH; Fan WY; Feng B; Liu WW; Chen RQ; Ban C; Dang AG; Wang M; Luo KT; Zhou GY; Yu FF; Ba Y · Nutrition reviews · 2024
    Meta-analysis2,334 participants14 studies pooledImmunity forVitamin C
  16. Effect of micronutrient supplements on influenza and other respiratory tract infections among adults: a systematic review and meta-analysis.
    Abioye AI; Bromage S; Fawzi W · BMJ global health · 2021
    Meta-analysisImmunity forVitamin C
  17. New evidence for antioxidant properties of vitamin C.
    Vojdani A; Bazargan M; Vojdani E; Wright J · Cancer detection and prevention · 2001
    Randomized trial20 participantsImmunity forVitamin C
  18. Enhanced Vitamin C Delivery: A Systematic Literature Review Assessing the Efficacy and Safety of Alternative Supplement Forms in Healthy Adults.
    Calder PC; Kreider RB; McKay DL · Nutrients · 2025
    Systematic review13 studies pooledImmunity forVitamin C
  19. Evaluation of the anti-wrinkle effect of an ascorbic acid-loaded dissolving microneedle patch via a double-blind, placebo-controlled clinical study.
    Lee C; Yang H; Kim S; Kim M; Kang H; Kim N; An S; Koh J; Jung H · International journal of cosmetic science · 2017
    Randomized trial23 participantsSkin Health forVitamin C
  20. Comparative Study on the Outcome of Periorbital Wrinkles Treated with Laser-Assisted Delivery of Vitamin C or Vitamin C Plus Growth Factors: A Randomized, Double-blind, Clinical Trial.
    Machado BHB; Frame J; Zhang J; Najlah M · Aesthetic plastic surgery · 2021
    Randomized trial149 participantsSkin Health forVitamin C
  21. Randomized trial of topical ascorbic acid in DMSO versus imiquimod for the treatment of basal cell carcinoma.
    Burke B; Bailie JE · Biomedicine & pharmacotherapy = Biomedecine & pharmacotherapie · 2022
    Randomized trial25 participantsSkin Health forVitamin C
  22. Vitamin C improves healing of foot ulcers: a randomised, double-blind, placebo-controlled trial.
    Gunton JE; Girgis CM; Lau T; Vicaretti M; Begg L; Flood V · The British journal of nutrition · 2022
    Randomized trial16 participantsSkin Health forVitamin C
  23. Dietary nutrient intakes and skin-aging appearance among middle-aged American women.
    Cosgrove MC; Franco OH; Granger SP; Murray PG; Mayes AE · The American journal of clinical nutrition · 2007
    Cross-sectional study4,025 participantsSkin Health forVitamin C
  24. Role of Oral Vitamin 'C' on Astigmatic Errors in Phacoemulsification.
    Mohan S; Sah K; Khattri M; Ahmad L; Sachan SK · Current eye research · 2021
    Randomized trial400 participantsVision Support forVitamin C
  25. Ascorbic acid metabolites are involved in intraocular pressure control in the general population.
    Hysi PG; Khawaja AP; Menni C; Tamraz B; Wareham N; Khaw KT; Foster PJ; Benet LZ; Spector TD; Hammond CJ · Redox biology · 2019
    Observational studyVision Support forVitamin C
  26. Nutritional modulation of cataract.
    Weikel KA; Garber C; Baburins A; Taylor A · Nutrition reviews · 2014
    Narrative reviewVision Support forVitamin C
  27. Dietary n-3 Fatty Acid, α-Tocopherol, Zinc, vitamin D, vitamin C, and β-carotene are Associated with Age-Related Macular Degeneration in Japan.
    Aoki A; Inoue M; Nguyen E; Obata R; Kadonosono K; Shinkai S; Hashimoto H; Sasaki S; Yanagi Y · Scientific reports · 2017
    Case-control study530 participantsVision Support forVitamin C
  28. Adherence to a Mediterranean diet, lifestyle and age-related macular degeneration: the Coimbra Eye Study - report 3.
    Raimundo M; Mira F; Cachulo MDL; Barreto P; Ribeiro L; Farinha C; Laíns I; Nunes S; Alves D; Figueira J; Merle BM; Delcourt C; Santos L; Silva R · Acta ophthalmologica · 2019
    Case-control study883 participantsVision Support forVitamin C