Most adults need 75 to 90 mg of vitamin C per day, an amount easily covered by a single serving of many fruits and vegetables. Women need 75 mg, men need 90 mg, and smokers need an extra 35 mg on top of that. These are the official Recommended Dietary Allowances, and they’re lower than many people assume.
Daily Requirements by Age and Sex
The RDA for vitamin C varies across life stages. For adult men, the target is 90 mg per day. For adult women, it’s 75 mg. Children need less, scaling up gradually: toddlers ages 1 to 3 need just 15 mg, kids ages 4 to 8 need 25 mg, and teenagers need 65 to 75 mg depending on sex.
Pregnancy and breastfeeding raise the bar. Pregnant women ages 19 to 50 need 85 mg per day, while breastfeeding women in the same age range need 120 mg. For pregnant and breastfeeding teens, the numbers are 80 mg and 115 mg respectively.
If you smoke, your body burns through vitamin C faster due to higher oxidative stress. Smokers need an additional 35 mg per day beyond the standard recommendation, which brings the total to about 125 mg for men and 110 mg for women. People regularly exposed to secondhand smoke likely benefit from the same increase.
Why the RDA Is Lower Than You’d Expect
Vitamin C supplement bottles commonly list doses of 500 mg or 1,000 mg per tablet. That’s 5 to 11 times the RDA for most adults. The gap between what’s recommended and what’s marketed creates real confusion.
Your body can only absorb so much vitamin C at once. At lower doses (under about 200 mg), your intestines absorb nearly all of it. As the dose climbs, absorption efficiency drops sharply. By the time you’re taking 1,000 mg or more, your body absorbs less than half and simply flushes the rest through your kidneys. This is why megadosing doesn’t proportionally increase the vitamin C in your blood or tissues. Splitting a larger dose into smaller amounts throughout the day improves absorption compared to taking it all at once.
The Upper Limit: 2,000 mg
The Tolerable Upper Intake Level for adults is 2,000 mg per day. This isn’t a target. It’s a ceiling, the amount below which most healthy adults won’t experience side effects. For children, the upper limit is lower, ranging from 400 mg for toddlers up to 1,800 mg for teenagers.
Going above 2,000 mg regularly can cause digestive problems. The most common complaints are diarrhea, nausea, and abdominal cramps. These happen because unabsorbed vitamin C draws water into the intestines. The symptoms typically resolve quickly once you reduce your intake.
There’s also the kidney stone question. High vitamin C intake can increase oxalate levels in urine, which theoretically raises kidney stone risk. The research on this is actually mixed, with studies showing conflicting results across doses ranging from 30 mg to 10,000 mg per day. The clearest risk is in people who already have a condition that causes high oxalate levels. If you have a history of kidney stones, it’s worth being cautious with high-dose supplements.
Vitamin C and the Common Cold
This is probably the most common reason people reach for extra vitamin C, and the reality is more modest than the marketing. A large Cochrane review covering over 9,700 cold episodes found that taking vitamin C daily (not just when you feel a cold coming on) shortened colds by about 8% in adults and 14% in children. In practical terms, that means a cold lasting 7 days might last about 6.5 days instead. Children taking 1 to 2 grams per day saw an 18% reduction in cold duration.
The key detail: these benefits came from taking vitamin C consistently every day before getting sick, not from starting it after symptoms appeared. Popping a megadose when you already have the sniffles doesn’t have the same effect.
Getting Enough From Food
A single medium orange provides roughly 70 mg of vitamin C, which nearly covers an adult woman’s entire daily need. A cup of raw red bell pepper delivers well over 100 mg. Strawberries, broccoli, kiwi, and tomatoes are all strong sources. Even a medium baked potato provides about 17 mg.
Most people eating a varied diet with several servings of fruits and vegetables daily are already meeting the RDA without a supplement. Vitamin C from food and supplements appears to be equally bioavailable, so there’s no absorption advantage to choosing one over the other. The advantage of food is that it comes packaged with fiber, other vitamins, and plant compounds that work together in ways a pill can’t replicate.
Cooking reduces vitamin C content because it breaks down in heat and dissolves in water. Steaming or microwaving preserves more than boiling. Eating some fruits and vegetables raw is the simplest way to maximize your intake.
Who Might Need a Supplement
Certain groups are more likely to fall short. Smokers have higher needs and often have lower dietary intake to begin with. People with very limited diets, whether due to food access, eating disorders, or medical conditions that restrict food variety, may not reach the RDA through food alone. Some digestive conditions also reduce absorption.
If you do supplement, a dose of 100 to 200 mg per day is enough to reach near-maximum blood levels in most healthy adults. Going higher than that offers diminishing returns since your body simply excretes the excess. For most people, a basic multivitamin or a low-dose vitamin C tablet fills any gaps without approaching levels that cause side effects.