Although not fully proven, large doses of vitamin C may help reduce how long a cold lasts. They do not protect against getting a cold. Vitamin C may also be helpful for those exposed to brief periods of severe or extreme physical activity.
The likelihood of success may vary from person to person. Some people improve, while others do not. Taking 1000 to 2000 mg per day can be safely tried by most people. Taking too much can cause stomach upset.
People with kidney disease should NOT take vitamin C supplements.
Large doses of vitamin C supplementation are not recommended during pregnancy.
A balanced diet almost always provides the required vitamin and minerals for the day.
Colds and vitamin C
Morse CG, High KP. Nutrition, immunity, and infection. In: Bennett JE, Dolin R, Blaser MJ, eds. Mandell, Douglas, and Bennett's Principles and Practice of Infectious Diseases, Updated Edition. 8th ed. Philadelphia, PA: Elsevier Saunders; 2015:chap 11.
National Institutes of Health, Office of Dietary Supplements website. Fact sheet for health professionals: vitamin C. www.ods.od.nih.gov/factsheets/VitaminC-Consumer/. Updated February 17, 2016. Accessed February 10, 2018.
Shah D, Sachdev HPS. Vitamin C (ascorbic acid). In: Kliegman RM, Stanton BF, St. Geme JW, Schor NF eds. Nelson Textbook of Pediatrics. 20th ed. Philadelphia, PA: Elsevier; 2016:chap 50.
Review Date 1/14/2018
Updated by: Linda J. Vorvick, MD, Clinical Associate Professor, Department of Family Medicine, UW Medicine, School of Medicine, University of Washington, Seattle, WA. Also reviewed by David Zieve, MD, MHA, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team.