Vitamin C RDA Calculator
Vitamin C (ascorbic acid) is a water-soluble vitamin that functions as an antioxidant and is essential for collagen synthesis, immune function, and iron absorption. The NIH Office of Dietary Supplements (ODS) sets the Recommended Dietary Allowance (RDA) at 90 mg per day for adult men and 75 mg per day for adult women. Smokers require an additional 35 mg per day. The tolerable upper intake level (UL) for adults is 2,000 mg per day. Enter your daily vitamin C intake from food and supplements, select your age group and sex, and the calculator shows your intake versus your RDA and the UL.
Vitamin C RDA by group (NIH ODS)
% of RDA = Intake (mg) / RDA (mg) * 100
RDA: men 90 mg, women 75 mg, pregnant 85 mg,
breastfeeding 120 mg, smokers add 35 mg
Tolerable Upper Level (UL): 2,000 mg/day
Values from the NIH Office of Dietary Supplements Vitamin C Fact Sheet (2021). Children and adolescents have lower RDAs; use the NIH ODS table for those values.
Vitamin C and health
- Vitamin C enhances non-heme iron absorption when consumed together with iron-rich plant foods.
- Most adults meet the RDA through a diet rich in fruits and vegetables without supplementation.
- Megadose supplementation (500-1,000 mg/day) is common but has limited evidence of benefit beyond RDA for most healthy adults.
- Vitamin C is water-soluble and excess is excreted in urine, making deficiency more likely than toxicity from dietary sources.
- People with kidney stones, especially those caused by oxalate, should use caution with high-dose vitamin C, as it can increase urinary oxalate.
Vitamin C RDA calculator: frequently asked questions
How much vitamin C do I need per day?
The NIH Office of Dietary Supplements sets the RDA for adult men at 90 mg per day and for adult women at 75 mg per day. Smokers need an additional 35 mg per day because smoking increases oxidative stress and vitamin C turnover. Pregnant women need 85 mg and breastfeeding women need 120 mg per day.
What is the tolerable upper intake level (UL) for vitamin C?
The tolerable upper intake level (UL) for vitamin C for adults is 2,000 mg per day. Amounts above the UL may cause digestive side effects such as diarrhoea, nausea, and abdominal cramping. High doses above 1,000 mg per day may also increase the risk of kidney stones in susceptible individuals.
What foods are high in vitamin C?
Rich sources include red bell pepper (190 mg per 1/2 cup), kiwifruit (64 mg each), orange juice (62 mg per 3/4 cup), broccoli (51 mg per 1/2 cup), and strawberries (49 mg per 1/2 cup). Most adults can meet the RDA through diet without supplementation.
What are the signs of vitamin C deficiency?
Severe deficiency causes scurvy, characterised by bleeding gums, poor wound healing, fatigue, and bruising. Scurvy is rare in the US but still occurs in populations with very limited fruit and vegetable intake. Plasma vitamin C below 11 micromol/L indicates deficiency.
Does vitamin C prevent colds?
Evidence from controlled trials shows that regular vitamin C supplementation (200 mg or more per day) modestly reduces the duration of colds by approximately 8-14% but does not significantly prevent colds in the general population. It may reduce incidence in people under heavy physical stress such as marathon runners.
Official sources
- NIH Office of Dietary Supplements: Vitamin C Fact Sheet for Health Professionals.
- USDA FoodData Central: FoodData Central (vitamin C content).
Reviewed by the CalculatorHub team, edited by James Graham, 15 June 2026. See our methodology.