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Can vitamin C prevent or treat COVID-19 (coronavirus)?

Medically reviewed by Carmen Pope, BPharm. Last updated on March 17, 2025.

Official Answer by Drugs.com

Why is vitamin C important?

Humans, unlike most animals, cannot make vitamin C, so we must obtain it from our diet.

It is vital for many different processes within our bodies. Vitamin C has the following key activities:

What evidence is there to support taking vitamin C for COVID-19?

There have been hundreds of studies investigating vitamin C, many of which have conflicting results. One of the biggest problems with vitamin C studies is that most do not measure vitamin C concentrations before or after supplementation. Supplementation is unlikely to show an effect in people whose vitamin C levels are already high.

COVID-19 is a new disease, and we are still learning about it. But several studies in other infections or conditions suggest it may be beneficial in certain groups of people, particularly those already deficient in vitamin C who develop COVID-19. Currently, at least two trials are underway specifically investigating the use of vitamin C to treat severe COVID-19, one in New York and one in China.

Beneficial effects of vitamin C supplementation have been reported for

These are just some of the studies that cite a beneficial response. A full analysis of all the research that involves vitamin C is beyond the scope of this answer.

What are the symptoms of vitamin C deficiency?

Vitamin C is a water-soluble vitamin, which means little is stored in the body and a deficiency can develop in as little as four to 12 weeks.

Studies have indicated that hypovitaminosis C (low vitamin C levels indicated by a plasma vitamin C of <23 umol/L) is the fourth leading vitamin deficiency in the United States.

Symptoms of low vitamin C include:

If left untreated, severe vitamin C deficiency (also known as Scurvy) can develop. Symptoms include:

More than two million sailors died from scurvy during the great voyages of discovery until Dr. James Lind, a Scottish surgeon in the Royal Navy, proved in 1753 that scurvy could be successfully treated with citrus fruit.

How much vitamin C should I be taking?

Recommended intakes of vitamin C (called Dietary Reference Intakes [DRIs]) have been developed by the Food and Nutrition Board. These are much higher than the amount required to prevent deficiency:

Whenever we have an infection or inflammation, our bodies require more vitamin C so your general intake should increase to cope with the extra demand.

Many factors can impair the absorption of vitamin C or increase a person’s requirement for it. The following people should include an extra 50-100mg of vitamin C per day in their diet or in the form of supplements:

Rates of vitamin C deficiency vary around the world with rates as low as 7.1% in the United States to nearly 74% in India. Total vitamin C deficiency manifesting as scurvy is rare.

Related questions

Can taking too much vitamin C cause side effects?

Yes. Taking more than 2000mg of vitamin C a day may cause stomach upsets, including abdominal pain, diarrhea or nausea.

Because vitamin C is a water-soluble vitamin, excessive vitamin C is excreted in the urine. Rarely, over-supplementation with vitamin C causes kidney stones.

What foods contain vitamin C?

In general, fruits contain more vitamin C than vegetables. Examples of foods that are high in vitamin C and the amount of vitamin C they contain include:

In general, raw fruits and vegetables contain higher quantities of vitamin C than boiled, although steaming and microwaving may reduce vitamin C losses. Prolonged storage can also reduce vitamin C levels.

Experts consider a diet that supplies 100–200 mg/day of vitamin C provides enough vitamin C to cover a healthy individual’s general requirements. People with medical conditions, such as cancer, diabetes, lung disease, or who smoke or exercise a lot should consider increasing their dietary intake of vitamin C.

Consuming five varied servings of fruits and vegetables a day can provide more than 200mg of vitamin C. Breastmilk is considered an adequate source of vitamin C in breastfeeding infants. Infant formula is already fortified with vitamin C.

When should people consider vitamin C supplements?

Vitamin C supplements are relatively cheap and should be considered in the following people whose diets may be deficient in vitamin C, or their absorption of vitamin C may be impaired, such as:

Men are also more likely than women to be deficient, probably because of a lower intake in general of fruits and vegetables.

Are some vitamin C supplements better than others?

Most vitamin C supplements contain synthetic vitamin C, which is made in a laboratory using a variety of different processes. This is the cheapest way of making vitamin C and there is no evidence to suggest that synthetic supplements are less effective than other forms of vitamin C at correcting a vitamin C deficiency.

More expensive vitamin C products often use whole foods; however, there may be some degradation in the vitamin C content during the production process, because vitamin C is not heat stable and degrades with time. Whole food supplements have the advantage that they include other factors, naturally present in foods, such as rutin, bioflavonoids, and other factors that potentially could aid absorption and utilization of vitamin C within our bodies.

Studies have been conflicting that have investigated if there is actually any difference in absorption between different forms of vitamin C, for example, synthetic vitamin C, Ester-C®, or vitamin C with bioflavonoids. Although one study showed higher vitamin C concentrations in leukocytes (white blood cells) with Ester C®, others did not.

Most organizations conclude that simple ascorbic acid (vitamin C) is the preferred source of supplemental vitamin C.

References
  1. Carr AC, Maggini S. Vitamin C, and Immune Function. Nutrients. 2017;9(11):1211. Published 2017 Nov 3. doi:10.3390/nu9111211
  2. Vitamin C. Fact Sheet for Health Professionals. National Institutes of Health. Office of Dietary Supplements. https://ods.od.nih.gov/factsheets/VitaminC-HealthProfessional/
  3. Maxfield L, Crane JS. Vitamin C Deficiency (Scurvy) [Updated 2019 Nov 19]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2020 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK493187/
  4. Hemilä H, Chalker E. Vitamin C Can Shorten the Length of Stay in the ICU: A Meta-Analysis. Nutrients. 2019;11(4):708. Published 2019 Mar 27. doi:10.3390/nu11040708
  5. Maxfield L, Crane J. Vitamin C Deficiency (Scurvy) Nov 19, 2019, https://www.ncbi.nlm.nih.gov/books/NBK493187/ Vitamin C. National Institutes of Health. https://ods.od.nih.gov/factsheets/VitaminC-HealthProfessional/

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