Daily Vitamin C Intake — 90 mg Men, 75 mg Women

The vitamin C RDA is 90 mg a day for men and 75 mg for women, with 35 mg added if you smoke. Both figures are easy to reach from food, which is most of the reason the supplement aisle’s claims outrun the evidence. Pick your life stage below.

The RDA by life stage

Life stage	Vitamin C per day
Children 4 to 8	25 mg
Ages 9 to 13	45 mg
Males 14 to 18	75 mg
Females 14 to 18	65 mg
Men 19 and older	90 mg
Women 19 and older	75 mg
Pregnancy 19 to 50	85 mg
Lactation 19 to 50	120 mg
Smokers	Add 35 mg to the figure above

The tolerable upper intake level is 2,000 mg a day for adults, 1,800 mg for ages 14 to 18 and 650 mg for children 4 to 8. The FDA Daily Value is 90 mg, so for once the label percentage matches the men’s target closely.

The smoker increment is a real DRI figure

The 35 mg is not a rule of thumb; it is in the 2000 DRI report, with the reasoning stated: smoking increases oxidative stress and metabolic turnover of vitamin C, so the requirement for smokers is increased by 35 mg/day. The report notes that a labeled-ascorbate study found turnover in smokers averaging roughly double that of non-smokers.

Practically: 125 mg for a man who smokes, 110 mg for a woman. Regular exposure to secondhand smoke is a reason to make sure you are comfortably at the standard RDA rather than at its edge.

What the cold evidence actually says

This is where a nutrition page earns its keep, because the popular belief and the federal summary do not match.

NCCIH’s evaluation of the research — 29 studies, more than 11,000 people — concludes that taking vitamin C does not prevent colds in the general population and shortens colds only slightly. And starting it once symptoms have begun does not affect length or severity at all. The megadose habit is treating a result the studies do not support.

The exception is narrow and specific. In people exposed to short periods of extreme physical stress — NCCIH names marathon runners and skiers — vitamin C cut the number of colds roughly in half. If you are not in that category, the general result is the one that applies to you.

What it does do

• Antioxidant, limiting oxidative damage to cells.
• Collagen synthesis, which is why deficiency shows up in skin, gums, blood vessels and wound healing, and why severe deficiency is scurvy.
• Immune function support — the ordinary kind, not the cold-proofing kind.
• Iron absorption: vitamin C is the strongest practical enhancer of non-heme iron uptake, the form that comes from plants.

That last one is the most actionable item on this page. Pairing a vitamin C source with beans, lentils or leafy greens in the same meal measurably improves how much iron you get from them — the daily iron intake page covers the multiplier vegetarians are working against. Zinc is the other mineral where absorption, not just intake, decides the outcome: see the daily zinc intake numbers.

Where to get it

Citrus, kiwi, strawberries, guava, bell peppers, broccoli and tomatoes all carry it, and a diet with several servings of fruit and vegetables clears the RDA without effort. Vitamin C is water-soluble and heat-sensitive, so raw or lightly cooked servings retain more than long-boiled ones, and surplus intake leaves in the urine rather than being stored.

Two cautions from NCCIH before anyone reaches for grams instead of milligrams: high doses cause diarrhea, nausea and stomach cramps; people with the iron-storage disease hemochromatosis should avoid them entirely; and anyone in cancer treatment or on cholesterol-lowering medication should talk to a clinician first. B12 is the other water-soluble vitamin where supplement doses vastly exceed the requirement — see the daily B12 intake page for why that gap exists there.

This content is informational and does not replace evaluation by a physician or registered dietitian.