Vitamin C
What’s New This Month
- Kidney stones: A 2026 review of 9 interventional studies found vitamin C raises oxalate, a stone-forming salt, in urine by 6.45 mg a day. 1
- Allergen recall: Vital Nutrients Aller-C was recalled in March 2026 for undeclared egg, soy and hazelnut. 2
- Lead notice: A California Prop 65 notice (2026-03906, August 2026) alleges lead in a vitamin C powder. 3
- Adverse-event reports: FDA received 110 reports naming a vitamin C product from October 2024 to mid-2026; a report does not show the product caused the event. 4
Overview
Vitamin C (ascorbic acid) is an essential vitamin. The body needs it to make collagen. Fruits and vegetables are the best sources, including citrus, peppers, kiwifruit and broccoli. 5
Supplements are sold as ascorbic acid, buffered ascorbates, Ester-C and liposomal forms. Labels claim immune support, cold relief, collagen and skin, and antioxidant protection.
How We Researched It
We rate each marketing claim with a modified version of GRADE, the system medical researchers use to say how sure we can be (i.e., high, moderate, low or very low), and check each trial with the Cochrane risk-of-bias tool, which asks whether a study’s design could skew its results. For vitamin C we used 24 records, published mostly from September 2022 through October 2026. We also checked FDA recall and warning-letter records, Prop 65 and NIH. No Cochrane update newer than 2013 was found.
Research NotesTop three benefits
Cold Prevention Under Extreme Stress GRADE: Low
In 5 trials of 598 marathon runners, skiers and soldiers, daily vitamin C halved colds (risk ratio 0.48). 6
Bias check: Only 598 people, in older trials. The review authors have long published in favor of vitamin C.
Shorter Colds in Children GRADE: Low
Across pooled trials, children’s colds were 14% shorter (range 7 to 21%). 6
Bias check: The range crosses our 15% bar, and the trials date from before 2013.
Blood Pressure GRADE: Low
In short trials, systolic pressure fell 3.8 mmHg (range 2.4 to 5.3) at a median 500 mg for 8 weeks. 7
Bias check: Trials were small and brief, and a later umbrella review of 6 pools found about 3.7 mmHg and rated certainty low. 8
Benefit Evaluation
| Claim | Claim Verdict | Research Confidence | Supporting Evidence | Safety Risk | Product Quality | FactStack™ Rating |
|---|---|---|---|---|---|---|
| Cold Prevention Under Extreme Stress | Promising | Low | Promising | Within Limits | Variable | Caution |
| Shorter Colds in Children | Promising | Low | Promising | Within Limits | Variable | Caution |
| Blood Pressure | Promising | Low | Promising | Within Limits | Variable | Caution |
| Symptom Severity | TBD | Low | TBD | Within Limits | Variable | Caution |
| Memory and Dementia Risk | TBD | Very Low | TBD | Within Limits | Variable | Caution |
| Collagen and Skin | TBD | Very Low | TBD | Within Limits | Variable | Caution |
| Sepsis | Doubtful | Low | Doubtful | Within Limits | Variable | Warning |
| Heart Protection | Doubtful | Low | Doubtful | Within Limits | Variable | Warning |
| Cancer Protection | Doubtful | Low | Doubtful | Within Limits | Variable | Warning |
| Uric Acid and Gout | Doubtful | Low | Doubtful | Within Limits | Variable | Warning |
| Cold Prevention and Immune Support | Unsupported | Moderate | Unconvincing | Within Limits | Variable | Warning |
| Shorter Colds in Adults | Unsupported | Moderate | Unconvincing | Within Limits | Variable | Warning |
| Starting at Onset | Unsupported | Moderate | Unconvincing | Within Limits | Variable | Warning |
| Iron Absorption and Iron Status | Unsupported | Moderate | Unconvincing | Within Limits | Variable | Warning |
What Sellers Say vs. What Studies Show
| “Vitamin C keeps colds away.” | In general-community trials of 10,708 people, colds were no less common (risk ratio 0.97). 6 |
| “Take it at the first sign of a cold.” | Starting vitamin C after symptoms begin showed no consistent effect. 6 |
| “It shortens colds a lot.” | Adults’ colds were 8% shorter, about half a day for a week-long cold. 6 |
| “More is better.” | Urinary oxalate rises with supplements, and men taking vitamin C had more kidney stones in two cohorts. 1 9 10 A 1.25 g oral dose peaked at 135 µmol/L in blood, versus 885 by IV. 11 |
| “Vitamin C fights COVID-19.” | FDA calls such claims unapproved-drug claims. In sepsis, the largest ICU trial of IV vitamin C found more death or organ failure. 12 Pooled benefit came only from small single-centre trials. 13 |
| “Liposomal C absorbs far better.” | It raised blood levels in 9 of 10 small studies, but no study showed a health benefit. 14 |
| “It protects your heart.” | In a Cochrane review, heart attack, stroke and death did not fall. 15 |
| “It fixes low iron.” | In 440 adults with iron-deficiency anemia, iron alone matched iron plus vitamin C. 16 |
| “It stops gout.” | Uric acid fell 0.35 mg/dL, a small drop, and no trial measured gout attacks. 17 |
Trial ParametersIf you try it
| Who | Adults with low intake or deficiency, or under sustained extreme physical or cold stress. |
| Dose | RDA 90 mg (men), 75 mg (women), plus 35 mg for smokers. About 200 mg a day matches trial doses. 5 |
| Ceiling | 2,000 mg a day, the NIH upper limit. Cold-at-onset plans of 6 to 8 g exceed it. 5 |
| Duration | No stop rule. Trials used it daily, started before illness. 6 |
| Form | Plain ascorbic acid tablet. No liposomal or buffered form has outcome evidence. Check multi-ingredient labels for allergens. 2 |
| Ask First | Kidney stones or disease; haemochromatosis; chemotherapy or radiation; statin with niacin; pregnancy; before a stool blood test. 5 |
How to Take It
| Pick a plan | If you take it, about 200 mg a day matches the trials. Eat fruits and vegetables first. 5 |
| Time of day | Not reported. |
| With food | Not reported. |
| What to expect | You will not feel it. Colds may be slightly shorter; under heavy physical stress, colds were half as common. 6 |
| How to take | Take it every day, before you get sick. High doses can cause diarrhea, nausea and cramps. 5 |
Works With / Don’t Mix With
✓ Works with
Daily use before illness. The cold benefits came from daily doses started before getting sick, not at the first sign. 6
Heavy physical or cold stress. Marathon runners, skiers and soldiers who took it had half as many colds. 6
⚠ Ask first / don’t mix
Chemotherapy or radiation. Antioxidants might protect tumor cells from these treatments; ask your cancer doctor. 5
Niacin with a statin. Vitamin C with other antioxidants may blunt the rise in HDL (good) cholesterol. 5
Guaiac stool blood tests. Vitamin C can cause false negatives; tell your doctor you take it. 18
Manufacturer Recalls & WarningsLast 36 months, newest first
| Date | Maker / Brand | Product | Action | Src |
|---|---|---|---|---|
| May 2026 | Llorens Pharmaceuticals International Division, Inc. | Vitamin B-Complex, Vitamin C & Folic Acid liquid, 8 fl oz | FDA Class II: black particles; 4,196 units in 23 states plus PR. Liquid, not a pill. | 19 |
| Mar 2026 | Vital Nutrients (Blueroot Health, Inc.) | Aller-C, 100 and 200 count | FDA Class II: undeclared egg, soy and hazelnut; 11,849 bottles in 40 states. Ongoing. | 2 |
| Sep 2025 | M.O.M Enterprises, LLC | Infant bedtime drops (elderberry and vitamin C blend), two recalls | FDA Class II: yeast spoilage; 85,248 and 46,752 units. Liquid drops, not a pill. | 20 |
Where to Buy
We compare products side-by-side not just on price, but on whether NSF lists the product as NSF/ANSI 173 Contents Certified (an independent lab confirms the label matches the contents), whether it is NSF Certified for Sport, whether USP lists it as USP Verified, and whether the seller says it is manufactured in the USA. We leave out a brand’s products for this supplement when, in the last 36 months, the FDA took action against that brand over this supplement (a Class I or II recall, a warning letter, an import alert or an advisory letter). We also leave out any brand with an FDA Class II recall or warning letter on any product. We also leave out any product named in a California Prop 65 notice or a non-US recall, along with that brand’s products of the same ingredient and form. Brands with other actions stay listed and are marked in the Recall Screen column. Our goal remains to provide you, the Consumer, with the information and data necessary to make an informed purchasing decision. Prices reflected below are static and subject to change.
Ratings above describe the ingredient’s research, not any product listed below.
| # | Retailer | Product | Price | NSF 173 | NSF Sport | USP | Mfg. in USA (per seller) | Recall Screen | Affiliate link |
|---|---|---|---|---|---|---|---|---|---|
| 1 | Amazon | Nature Made Extra Strength Vitamin C 1000 mg, 100 Tablets | Check Price | ✓ | ✓ | ✓ | View on Amazon ↗ | ||
| 2 | Amazon | BUBS Naturals BUBS Boost Vitamin C with Bioflavonoids, 90 Capsules | Check Price | ✓ | ✓ | ✓ | View on Amazon ↗ | ||
| 3 | Amazon | THORNE Vitamin C 500 mg with Citrus Bioflavonoids, 90 Capsules | Check Price | ✓ | ✓ | ✓* | View on Amazon ↗ | ||
| 4 | iHerb | Nature's Bounty, Vitamin C, 500 mg, 100 Tablets | $6.69 | ✓ | ✓ | View on iHerb ↗ | |||
| 5 | iHerb | Bio Nutrition, Vitamin C, 1,000 mg, 90 Tablets | $8.79 | ✓ | ✓ | View on iHerb ↗ | |||
| 6 | HerbsPro | Solgar, Vitamin C, 1000 Mg, 100 Veg Caps | $15.37 | ✓ | ✓ | View on HerbsPro ↗ | |||
| 7 | Green's Nutrition | Superior Source Vitamin C Sour Cherry Melts 90 Tabs | $17.49 | ✓ | ✓ | View on Green's Nutrition ↗ | |||
| 8 | Green's Nutrition | Superior Source Vitamin C Melts Tangy Orange 90 Tabs | $17.49 | ✓ | ✓ | View on Green's Nutrition ↗ | |||
| 9 | HerbsPro | Now Foods, Liposomal Vitamin C, 120 VegCaps | $18.74 | ✓ | ✓* | View on HerbsPro ↗ | |||
| 10 | HerbsPro | Solgar, Vitamin C, 500 mg, 250 V Caps | $22.72 | ✓ | ✓ | View on HerbsPro ↗ |
Sources
1. Farkouh et al. Vitamin C supplements and urinary oxalate: review of 9 interventional studies. Journal of Endourology 40(11):1242, 2026. doi.org/10.1177/08927790261471733
2. Recall H-0663-2026: Vital Nutrients Aller-C (undeclared egg, soy, hazelnut). US Food and Drug Administration (openFDA food enforcement), Mar to Apr 2026. api.fda.gov/food/enforcement.json?search=recall_number.exact:%22H-0663-2026%22
3. Notice of Violation 2026-03906: vitamin C powder (lead). California Office of the Attorney General, Proposition 65, 7 Aug 2026. oag.ca.gov/prop65/60-day-notice-2026-03906
4. FDA CAERS adverse-event reports naming vitamin C (110 in Oct 2024 to mid-2026 window). US Food and Drug Administration (openFDA food event), accessed 10 Oct 2026. api.fda.gov/food/event.json?search=products.name_brand:%22vitamin%20c%22+AND+date_created:[20241010+TO+20261010]
5. Vitamin C: Fact Sheet for Health Professionals. NIH Office of Dietary Supplements, updated 31 Jul 2025. ods.od.nih.gov/factsheets/VitaminC-HealthProfessional/
6. Hemilä H, Chalker E. Vitamin C and the common cold (Cochrane review). Cochrane Database of Systematic Reviews CD000980.pub4, 2013. doi.org/10.1002/14651858.CD000980.pub4
7. Juraschek SP et al. Effects of vitamin C supplementation on blood pressure: meta-analysis. American Journal of Clinical Nutrition 95:1079, 2012. pubmed.ncbi.nlm.nih.gov/22492364/
8. Kosari et al. Vitamin C and blood pressure: umbrella review of 6 meta-analyses. Food & Function 17:2643, 2026. pubmed.ncbi.nlm.nih.gov/41784995/
9. Ferraro PM et al. Total, dietary and supplemental vitamin C intake and kidney stones. American Journal of Kidney Diseases 67:400, 2016. doi.org/10.1053/j.ajkd.2015.09.005
10. Thomas LD et al. Ascorbic acid supplements and kidney stone incidence among men. JAMA Internal Medicine 173:386, 2013. doi.org/10.1001/jamainternmed.2013.2296
11. Padayatty SJ et al. Vitamin C pharmacokinetics: oral versus intravenous dosing in healthy volunteers. Annals of Internal Medicine 140:533, 2004. pubmed.ncbi.nlm.nih.gov/15068981/
12. Lamontagne F et al. Intravenous vitamin C in adults with sepsis in the ICU (LOVIT). New England Journal of Medicine 386:2387, 2022. doi.org/10.1056/NEJMoa2200644
13. Cai B et al. Intravenous vitamin C in sepsis: meta-analysis of 14 trials. Frontiers in Nutrition 13:1905726, 24 Aug 2026. doi.org/10.3389/fnut.2026.1905726
14. Carr AC et al. Liposomal vitamin C bioavailability: scoping review. Basic & Clinical Pharmacology & Toxicology 137(1):e70067, 2025. pubmed.ncbi.nlm.nih.gov/40506693/
15. Al-Khudairy L et al. Vitamin C supplementation for the primary prevention of cardiovascular disease (Cochrane review). Cochrane Database of Systematic Reviews CD011114.pub2, 2017. pubmed.ncbi.nlm.nih.gov/28301692/
16. Li N et al. Iron with or without vitamin C in iron-deficiency anemia: randomized trial of 440 adults. JAMA Network Open, 2020. doi.org/10.1001/jamanetworkopen.2020.23644
17. Juraschek SP et al. Effect of vitamin C supplementation on serum uric acid: meta-analysis of trials. Arthritis Care & Research (PMID 21671418), 2011. pubmed.ncbi.nlm.nih.gov/21671418/
18. Jaffe RM et al. False-negative stool occult blood tests caused by ingestion of ascorbic acid. Annals of Internal Medicine 83(6):824, 1975. doi.org/10.7326/0003-4819-83-6-824
19. Recall H-0809-2026: Llorens B-Complex, Vitamin C and Folic Acid liquid (black particles). US Food and Drug Administration (openFDA food enforcement), May 2026. api.fda.gov/food/enforcement.json?search=recall_number.exact:%22H-0809-2026%22
20. Recalls H-0576-2025 and H-0025-2026: M.O.M Enterprises infant bedtime drops (yeast). US Food and Drug Administration (openFDA food enforcement), Sep to Oct 2025. api.fda.gov/food/enforcement.json?search=recall_number.exact:%22H-0576-2025%22
21. Import Alert 54-14: dietary supplements from firms not meeting GMP. US Food and Drug Administration, June 2025. www.accessdata.fda.gov/cms_ia/importalert_741.html
