How much vitamin C should I take daily?

The official daily recommendation for vitamin C is 90mg for men and 75mg for women, and there is a serious argument in the research literature that this is roughly half of what most adults should aim for.

That gap is not academic. In US survey data from 2003–2006, 41.8% of adults had insufficient blood levels of vitamin C, and once daily intake passes 1,000mg, the gut absorbs less than half of what you take.

This guide covers the three numbers that matter — 75–90mg, 200mg and 2,000mg — and how to find your own vitamin C dosage.

Table of Contents

1. What the Official Vitamin C Dosage Guidelines Recommend
2. Why Researchers Argue the RDA Is a Floor, Not a Target
3. What Actually Happens When You Take 1,000mg
4. How Much Vitamin C Should You Take Daily?
5. The Upper Limit — and Who Should Stay Well Below It
6. Timing: Splitting Doses and When to Take Them
7. When Delivery Format Changes the Dosing Maths
8. Frequently Asked Questions
9. Conclusion
10. Research References

1. What the Official Vitamin C Dosage Guidelines Recommend

The Recommended Dietary Allowance, set by the Food and Nutrition Board of the US National Academies, is 90mg per day for adult men and 75mg per day for adult women. It was pitched at the intake that keeps white blood cells near saturation with minimal loss in urine, and people who smoke need an extra 35mg a day because smoking speeds up the vitamin's turnover. The same Dietary Reference Intake values are used in Canada.

The RDA is not a target for optimal health. It is the intake estimated to meet the needs of 97–98% of healthy people: a floor set to prevent inadequacy, not a ceiling set to maximise anything. That distinction explains most of the confusion about how much to take.

In the 2001–2002 national survey, average US intakes already sat above the RDA, at 105.2mg a day for adult men and 83.6mg a day for adult women. Averages hide a wide spread, though, and the 2,000mg tolerable upper intake level leaves a very large gap between "enough to avoid scurvy" and "as much as is safe."

How Much Vitamin C Per Day for a Woman?

For women aged 19 and over, the RDA is 75mg of vitamin C a day, or 110mg if you smoke. The 2,000mg daily upper limit is the same for women as for men.

The 15mg gap between the sexes rests on thinner evidence than it looks. When the current figures were set, no comparable dosing study existed in women, so their RDA was extrapolated from data in men on the basis of body weight. NIH researchers then kept healthy young women on a hospital ward for an average of 186 days, testing daily doses from 30mg to 2,500mg. Their plasma and circulating blood cells were saturated at 400mg a day, and the team concluded that the RDA for young women should be 90mg, the same as for men.

The picture at higher doses also differs by sex. In the Nurses' Health Studies, which followed 156,735 women for a median of more than 11 years, neither total nor supplemental vitamin C intake was linked to kidney stones, although the same analysis found a link in men. On the other hand, a Swedish study of 24,593 women found that taking vitamin C supplements was associated with a 25% higher risk of cataract surgery, even though higher intakes from food have been linked to lower cataract risk. It is an observational link, not proof of harm, but another reason not to assume more is better.

In practice, the vitamin C dosage ranges in this guide apply to women much as they do to men, and women tend to start from a stronger position: in 2017–2018 US survey data, men averaged about 10 µmol/L less vitamin C in their blood than women. Requirements change during pregnancy and breastfeeding, so check those with your healthcare provider.

2. Why Researchers Argue the RDA Is a Floor, Not a Target

The most influential dosing work in this field is a 1996 depletion–repletion study in which seven hospitalised volunteers were taken down to under 5mg of vitamin C a day and then given escalating doses from 30mg up to 2,500mg. The steep part of the dose–response curve sat between 30mg and 100mg a day, and bioavailability was complete for a single 200mg dose.

Building on that work, a group of vitamin C researchers argued in a 2012 perspective paper that 200mg a day is the optimum intake for most adults, the level they judged to offer the most potential benefit with the least risk of inadequacy or adverse effects. The Linus Pauling Institute describes plasma levels reaching a steady state of 60–80 µmol/L at doses of 200–400mg a day in healthy young adults.

The Institute's own recommendation goes further, at 400mg a day for generally healthy adults, the intake at which NIH studies found blood and circulating cells fully saturated in young, healthy nonsmokers. The Institute acknowledges that the evidence on optimum intake is incomplete. What this work shows is where blood levels plateau, not that everyone taking 200mg or 400mg will see a measurable health benefit over someone taking the RDA.

3. What Actually Happens When You Take 1,000mg

Vitamin C absorption is not linear. The NIH reports that roughly 70–90% is absorbed at moderate intakes of 30–180mg a day, but absorption falls below 50% at doses above 1 gram a day. The transporters that move vitamin C across the gut wall are saturable, and once they are saturated, additional milligrams largely pass through.

The 1996 pharmacokinetic data makes the same point from the excretion side: at single doses of 500mg and above, bioavailability declined and the absorbed amount was simply excreted in urine. Six of the seven volunteers excreted no vitamin C at all until the 100mg dose.

• At 200mg in a single dose, absorption is essentially complete
• Above 500mg in a single dose, a growing share is absorbed and then excreted
• Above 1,000mg a day, less than half of what you swallow is absorbed at all

This is the central reason a 1,000mg tablet does not deliver 1,000mg to your tissues, and it is covered in detail in our guide to why most of a vitamin C dose is wasted.

4. How Much Vitamin C Should You Take Daily?

The official answer is 75mg a day for women and 90mg for men, plus 35mg if you smoke. Research suggests about 200mg a day is a better target for most healthy adults, and your total from food and supplements should be no more than 2,000mg a day, the tolerable upper intake level.

Standalone supplements often go much higher: in one large Swedish study, ascorbic acid tablets typically contained 1,000mg. That is within the upper limit but well past the point where blood levels plateau, and section 5 explains why men should be cautious at that level.

Circumstances shift the number upward:

• People who smoke need 35mg a day more, and in 2003–2006 survey data 60.8% of smokers had insufficient vitamin C levels, compared with 34.8% of non-smokers. See why smokers have higher vitamin C requirements.
• People eating few fruits and vegetables, because five servings a day generally provide about 150–200mg, and fewer servings fall short of that. See the highest food sources of vitamin C.
• Older adults and people who are unwell or under stress, because a meta-analysis of 36 studies found older adults need a substantially higher intake to reach the blood levels younger adults achieve.

A practical approach to vitamin C dosage is to start at the low end of whatever range applies, hold it for a few weeks, and adjust only if there is a reason to. Because plasma levels plateau at around 60–80 µmol/L on standard oral vitamin C, pushing far beyond 400mg a day changes blood levels much less than the dose suggests.

5. The Upper Limit — and Who Should Stay Well Below It

The tolerable upper intake level for adults is 2,000mg a day. It was set to prevent diarrhoea and gastrointestinal disturbance at high supplemental intakes, which are the most common and most reversible adverse effects.

Kidney stones are the more serious question. An 11-year prospective study of 23,355 Swedish men with no history of stones found that ascorbic acid supplement users had roughly double the incidence of kidney stones, with a relative risk of 1.95 (95% CI 1.35–2.81) and a dose–response trend: 1.66 for fewer than seven tablets a week and 2.23 for seven or more. In absolute terms, that is roughly one extra case for every 680 men taking them each year. A larger US analysis points the same way: among 40,536 men, total vitamin C intakes of 1,000mg a day or more were linked to a 43% higher kidney stone risk, while vitamin C from food alone showed no link in men or women.

Caution is warranted rather than alarm. The authors of the Swedish study advise that high-dose preparations be avoided, particularly by people with a history of kidney stones. Talk to a physician before supplementing at 1,000mg or more if you have kidney disease, a history of stones, or haemochromatosis or another iron-overload condition, and before starting any vitamin C supplement if you take regular medication. The full picture is in vitamin C side effects and the upper limit, and the megadose case is examined in our guide to high-dose vitamin C.

6. Timing: Splitting Doses and When to Take Them

Because absorption is essentially complete up to about 200mg at a time but falls off above 500mg, splitting your vitamin C dosage across the day extracts more from the same total. Two 250mg doses will generally deliver more absorbed vitamin C than one 500mg dose, and the Linus Pauling Institute advises taking large amounts in divided doses to keep blood levels consistently high.

Vitamin C is water-soluble and does not need food to be absorbed, though taking it with a meal is a common way to reduce the stomach discomfort some people notice at higher doses. There is no strong evidence favouring morning over evening.

Consistency matters more than timing. In the 2013 Cochrane review, regular supplementation of 0.2g a day or more shortened colds by 8% in adults and 14% in children (31 comparisons, 9,745 colds). It did little to prevent colds in the general population (29 comparisons, 11,306 participants; risk ratio 0.97), though in people under heavy short-term physical stress, such as marathon runners, skiers and soldiers, five trials in 598 participants found the risk roughly halved (risk ratio 0.48).

7. When Delivery Format Changes the Dosing Maths

Everything above assumes standard ascorbic acid, where absorption efficiency drops as the dose climbs. Liposomal delivery wraps vitamin C in a phospholipid shell, and a 2025 scoping review found AUC improvements of 1.3–7.2× over non-liposomal forms in 9 of 10 trials. AUC, or area under the curve, measures total exposure in the blood over time. The UK Committee on Toxicity's 2025 review found only a handful of controlled human studies, six in all, some of them small.

The honest framing matters here. The absorption advantage is well documented in 9 of those 10 trials, but better clinical outcomes in people who are already replete have not been established, and the scoping review calls for research on biological effects. The Committee on Toxicity added a further caution: at standard doses, vitamin C is already fully bioavailable. Better absorption is a reason to expect more of a large dose to reach your blood, not a reason to expect a different result.

Bio Absorb Nutraceuticals makes its Liposomal Vitamin C in a GMP-certified Canadian facility, in two formats: a liquid that mixes with water or juice, and capsules that need no refrigeration and travel well. For anyone working out a dose, the liquid allows finer adjustment, which helps if you split a total across the day, while the capsules are simpler to keep consistent. For most people consistency matters more than precision, which is an argument for whichever format you will actually remember to take.

Both are verified corn-free, which is unusual in a category where most ascorbic acid is corn-derived. That distinction is irrelevant to most people and decisive for a few: for anyone with a corn allergy or sensitivity, it can be the difference between tolerating a daily supplement and giving up on one. Both are also non-GMO, gluten-free, nut-free, dairy-free and vegan, every batch is third-party tested, and both are covered by a money-back guarantee.

The delivery system is what ties this back to vitamin C dosage. If absorption efficiency is the thing limiting a standard dose, then the format is part of the arithmetic, not just the number on the front of the bottle. See current serving details for the liquid or the full product specification for the capsules. Background on the delivery system is in our complete guide to liposomal vitamin C.

Frequently Asked Questions

Is 1,000mg of vitamin C a day too much?

It is half the 2,000mg upper limit, so it is within the accepted safe range for most healthy adults, but it is inefficient: absorption drops below 50% above 1 gram a day. Men, and anyone with a history of kidney stones, should check with a physician first, because the Swedish study linking supplements to stones involved tablets of about 1,000mg.

Can I take vitamin C on an empty stomach?

Yes. It is water-soluble and does not need dietary fat to be absorbed. Some people find high doses cause stomach upset or loose stools, the effect the 2,000mg upper limit was set to prevent, and taking it with food usually helps.

Do women need less vitamin C than men?

On paper, yes: the RDA is 75mg a day for women and 90mg for men. But the women's figure was extrapolated from data in men, and a later NIH study in healthy young women concluded their RDA should also be 90mg. In practice, the two figures are close enough that the same vitamin C dosage ranges apply to both.

Does liposomal vitamin C mean I can take a smaller dose?

Possibly, though nobody has established the equivalence precisely. The 1.3–7.2× AUC range reported in the 2025 scoping review is wide, and it describes blood exposure rather than clinical effect. Treat it as a reason a given dose may go further, not as a fixed conversion factor.

What happens if I take too much vitamin C?

The most common effects are gastrointestinal, such as diarrhoea, cramping and nausea, and they usually resolve when the dose comes down. The longer-term concern is oxalate: the 1996 pharmacokinetic study found oxalate and urate excretion elevated at 1,000mg a day compared with lower doses, which is the proposed mechanism behind the kidney stone signal.

Can I get enough vitamin C from food alone?

Yes, if you eat enough produce: five servings of fruit and vegetables a day generally provide about 150–200mg, comfortably above the RDA and close to the 200mg research target. Supplements do move the numbers, though. In 2017–2018 US survey data, people taking a vitamin C–containing supplement averaged 27 µmol/L more vitamin C in their blood, so supplementation is a reasonable way to close a persistent gap.

Conclusion

The 75–90mg RDA prevents deficiency, the 200mg mark is where the pharmacokinetic evidence points for most healthy adults, and 2,000mg is the ceiling, but the right vitamin C dosage depends on absorption as much as on the number on the label. If you want your dose to go further, see current pricing and serving details for Bio Absorb's Liposomal Vitamin C liquid.

Research References

1. Vitamin C pharmacokinetics in healthy volunteers: evidence for a recommended dietary allowance. Proceedings of the National Academy of Sciences, Vol. 93, No. 8 (1996), pp. 3704–3709. Complete bioavailability at a single 200mg dose, declining from 500mg; oxalate and urate excretion rose at 1,000mg a day.
2. A new recommended dietary allowance of vitamin C for healthy young women. Proceedings of the National Academy of Sciences, Vol. 98, No. 17 (2001), pp. 9842–9846. Blood saturated at 400mg a day; the RDA for young women should be 90mg.
3. Authors' Perspective: What is the Optimum Intake of Vitamin C in Humans? Critical Reviews in Food Science and Nutrition, Vol. 52, No. 9 (2012), pp. 815–829. Concludes that 200mg a day is the optimum intake for most adults.
4. Do Liposomal Vitamin C Formulations Have Improved Bioavailability? A Scoping Review Identifying Future Research Directions. Basic & Clinical Pharmacology & Toxicology, Vol. 137 (2025), article e70067. 1.3–7.2× higher AUC for liposomal vitamin C in 9 of 10 trials; calls for research on biological effects.
5. Vitamin C for preventing and treating the common cold. Cochrane Database of Systematic Reviews, Issue 1 (2013), Art. No. CD000980. Regular supplementation shortened colds by 8% in adults and 14% in children; incidence fell only under heavy physical stress.
6. Ascorbic Acid Supplements and Kidney Stone Incidence Among Men: A Prospective Study. JAMA Internal Medicine, Vol. 173, No. 5 (2013), pp. 386–388. Supplement users had a relative risk of 1.95 and 147 extra cases per 100,000 person-years.
7. Total, Dietary, and Supplemental Vitamin C Intake and Risk of Incident Kidney Stones. American Journal of Kidney Diseases, Vol. 67, No. 3 (2016), pp. 400–407. Total and supplemental vitamin C linked to kidney stones in men but not women.
8. Insufficient Vitamin C Levels among Adults in the United States: Results from the NHANES Surveys, 2003–2006. Nutrients, Vol. 13, No. 11 (2021), article 3910. 41.8% of US adults, and 60.8% of smokers, had insufficient levels.
9. Vitamin C Status of US Adults Assessed as Part of the National Health and Nutrition Examination Survey Remained Unchanged between 2003–2006 and 2017–2018. The Journal of Applied Laboratory Medicine, Vol. 8, No. 2 (2023), pp. 272–284. Status unchanged since 2003–2006; men about 10 µmol/L lower than women; supplement users 27 µmol/L higher.
10. Dietary Reference Intakes for Vitamin C, Vitamin E, Selenium, and Carotenoids: Vitamin C. Institute of Medicine, National Academies Press (2000). Set the current RDAs and the 2,000mg upper limit.
11. Vitamin C: Fact Sheet for Health Professionals. National Institutes of Health, Office of Dietary Supplements (accessed September 2026). Source for the RDAs, absorption rates, average intakes and the Swedish cataract finding.
12. Vitamin C: Micronutrient Information Center. Linus Pauling Institute, Oregon State University (accessed September 2026). Plasma plateau of 60–80 µmol/L at 200–400mg a day; full absorption up to 200mg per dose.
13. Vitamin C: Pauling Recommendation. Linus Pauling Institute, Oregon State University (accessed September 2026). The Institute's 400mg a day recommendation and the evidence behind it.
14. Rx for Health. Linus Pauling Institute, Oregon State University (accessed September 2026). Five servings of fruit and vegetables provide about 150–200mg; take large amounts in divided doses.
15. Novel formulations of supplement compounds designed to increase oral bioavailability. UK Committee on Toxicity of Chemicals in Food, Consumer Products and the Environment, GOV.UK (2025). Vitamin C is fully bioavailable at standard doses.

About the Author

David Kimbell is a health writer, digital entrepreneur and former aerospace engineer, based in Ottawa, Canada. He loves translating complex science into clear, actionable guidance for consumers seeking evidence-based solutions.

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Important Disclaimers

Medical Disclaimer: This article provides educational information only and is not intended as medical advice. Always consult with a qualified healthcare provider before starting any new supplement, especially if you have existing health conditions, take medications, or are pregnant or nursing.

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