Most adults need 75 to 90 mg of vitamin C per day, an amount easily covered by a single orange or a cup of strawberries. That’s the official recommendation from the National Institutes of Health: 90 mg daily for men and 75 mg for women. But your ideal intake shifts based on age, whether you smoke, and whether you’re pregnant or breastfeeding.
Daily Recommendations by Age and Sex
Vitamin C needs are lowest in early childhood and climb steadily through adolescence. Children ages 1 to 3 need just 15 mg per day, while kids 4 to 8 need 25 mg. By the time children reach 9 to 13, the target rises to 45 mg. In the teen years, recommendations split by sex for the first time: boys 14 to 18 need 75 mg, and girls the same age need 65 mg.
For adults 19 and older, the numbers settle at 90 mg for men and 75 mg for women. These amounts are designed to maintain healthy tissue repair, support your immune system, and act as an antioxidant. They’re not hard to reach through food. A medium red bell pepper has about 150 mg, a cup of broccoli has around 80 mg, and a single kiwi delivers roughly 70 mg.
Smokers Need More
If you smoke, add 35 mg per day to the standard recommendation. That puts the target at 125 mg for men and 110 mg for women. Smoking accelerates the rate at which your body uses up vitamin C, leaving less available for immune function and cell repair. The same applies if you’re regularly exposed to secondhand smoke, though no separate number has been set for that group.
Pregnancy and Breastfeeding
Pregnant women ages 19 to 50 need 85 mg per day, a modest bump above the baseline. Teens who are pregnant need 80 mg. The bigger jump comes during breastfeeding: 120 mg per day for adults and 115 mg for teens. The extra vitamin C supports fetal development and helps maintain levels in breast milk, since the vitamin passes directly to the baby through nursing.
Vitamin C and the Common Cold
This is where expectations often outpace reality. A large Cochrane review of clinical trials found that taking vitamin C after cold symptoms start does not consistently shorten how long you’re sick or reduce severity. One large trial did report a benefit from an 8-gram dose taken at symptom onset, and two smaller trials using five-day supplementation showed some effect, but across seven trial comparisons involving over 3,200 cold episodes, the results were inconsistent.
In other words, loading up on vitamin C once you already feel a scratchy throat is unlikely to make a meaningful difference. Regular daily intake at normal levels supports your immune system overall, but megadosing during illness isn’t well supported by the evidence.
How Much Is Too Much
Your body can only absorb so much vitamin C at once. At doses around 200 mg, absorption is highly efficient. As doses climb past that, your intestines absorb a smaller and smaller percentage, and your kidneys flush the excess. This is why taking a 1,000 mg supplement doesn’t give you ten times the benefit of a 100 mg dose.
The tolerable upper limit for adults is 2,000 mg per day. Going above that raises the risk of digestive problems like diarrhea, nausea, and stomach cramps. But kidney stone risk can increase at lower amounts. Research published in European Urology Open Science found that daily supplementation of 1,000 mg significantly raised urinary oxalate levels, a key driver of kidney stones. In one study, people taking 1,000 mg per day saw their 24-hour oxalate output jump from 31 mg to 50 mg. Among men specifically, doses of 1,000 mg or more were linked to a higher risk of developing kidney stones for the first time. That association wasn’t seen in women, but the safest approach for anyone prone to kidney stones is to stay well below 1,000 mg from supplements.
Supplement Forms and Absorption
Standard ascorbic acid, the cheapest and most common form of supplemental vitamin C, is well absorbed at typical doses. You’ll also see buffered forms (like calcium ascorbate or sodium ascorbate) marketed as gentler on the stomach, which can be true if regular ascorbic acid causes you digestive discomfort.
Liposomal vitamin C, which wraps the vitamin in a fat-based capsule, is marketed as having superior absorption. One small report suggested it may be better absorbed than non-encapsulated forms, but according to the Linus Pauling Institute, large-scale studies comparing its bioavailability to standard ascorbic acid haven’t been done yet. For most people taking a reasonable daily dose, regular ascorbic acid works fine. Splitting a larger dose into two smaller ones taken hours apart will improve absorption more than switching to a premium formulation.
Interactions With Medications
High-dose vitamin C can interfere with several common medications. If you take statins or niacin for high cholesterol, vitamin C supplements may reduce their effectiveness. The same applies to certain antiviral drugs called protease inhibitors. Vitamin C can also increase how much aluminum your body absorbs from antacids and phosphate binders, which is especially risky if you have kidney problems. And for women on birth control pills or hormone replacement therapy, supplemental vitamin C can raise estrogen levels.
These interactions generally become relevant at supplemental doses, not from the vitamin C in a salad. If you take any of these medications and want to add a vitamin C supplement, it’s worth discussing timing and dosage with your pharmacist.
Practical Takeaway
For most adults, 75 to 90 mg per day from food or a basic supplement covers your needs. Smokers should aim for about 125 mg. Pregnant and breastfeeding women need 85 to 120 mg depending on their stage. There’s little evidence that megadoses prevent or treat colds, and staying under 1,000 mg from supplements is the safer choice for your kidneys. If your diet regularly includes fruits and vegetables, you may not need a supplement at all.