What vitamin C does in your body

Vitamin C is a nutrient your body uses to build and repair tissue, fight off infections, and protect your cells from damage. Your body cannot make it on its own, so you need to get it from food or supplements. It works by supporting your immune system, helping wounds heal, and acting as an antioxidant — meaning it neutralizes harmful molecules that can wear down your cells over time.

You may have heard that vitamin C prevents colds. The research is more nuanced than that. For most people, taking extra vitamin C does not stop a cold from starting. However, for people under intense physical stress — like athletes training hard or people in very cold climates — regular vitamin C intake may shorten how long a cold lasts by a day or so. If you are already sick, taking it then does not appear to help.

Vitamin C also helps your body absorb iron from plant-based foods, which matters if you eat little or no meat. It supports collagen production, which keeps your skin, joints, and connective tissue intact. And it may help lower blood pressure slightly and reduce the risk of heart disease, though the evidence is still developing.

Key Takeaways

  • Vitamin C supports immune function, wound healing, and cell protection, but taking extra amounts does not prevent colds in most people.
  • Most adults need 75 to 90 milligrams daily, which you can get from common foods like oranges, strawberries, bell peppers, and broccoli.
  • Your body does not store vitamin C, so you need a source every day — either from food or a supplement.
  • Supplements are available as tablets, powders, and gummies, and more is not always better; excess amounts are excreted in urine.

How much vitamin C you need each day

The recommended daily amount depends on your age and sex. Adult men need 90 milligrams per day, and adult women need 75 milligrams. If you smoke, add an extra 35 milligrams to that number, because smoking depletes vitamin C in your body. Pregnant people need 85 milligrams, and those who are breastfeeding need 120 milligrams.

These amounts are set by the National Institutes of Health and are based on what keeps most healthy people functioning well. They are not the same as the upper limit — the amount beyond which side effects become more likely. For vitamin C, that upper limit is 2,000 milligrams per day for adults. Your body excretes anything beyond what it needs, so taking 500 milligrams is not "better" than taking 100 milligrams; the extra straightforward leaves your body in urine.

Food sources of vitamin C

You can meet your daily vitamin C needs through food alone. Citrus fruits are well known — one medium orange has about 70 milligrams — but many other foods are equally good or better. One cup of raw bell peppers (red, yellow, or orange) contains 150 to 200 milligrams. One cup of strawberries has about 100 milligrams. Broccoli, kiwi, tomatoes, and Brussels sprouts all contain significant amounts.

Vitamin C is sensitive to heat and air, so raw or lightly cooked vegetables retain more than heavily cooked ones. Frozen vegetables often preserve vitamin C well because they are frozen soon after harvest. Canned fruits packed in juice also retain most of their vitamin C. If you eat a variety of fruits and vegetables throughout the day, you will likely meet your daily need without thinking about it.

Some foods are fortified with vitamin C — meaning it has been added during manufacturing. Orange juice, breakfast cereals, and some plant-based milk alternatives often have added vitamin C. Check the label to see how much is in each serving.

Vitamin C supplements: forms and how to use them

Supplements come in several forms: tablets, capsules, powders, gummies, and liquids. The most common form is ascorbic acid, which is chemically identical to the vitamin C in food. Other forms — like calcium ascorbate or sodium ascorbate — are buffered versions that may be gentler on the stomach if you take large doses. Some brands sell "natural" vitamin C derived from rosehips or kakadu plums, but your body processes it the same way as synthetic versions.

Dosage varies widely. Some supplements contain 250 milligrams, others 1,000 or more. For most people, a single dose of 500 to 1,000 milligrams is sufficient if you are not getting enough from food. Taking it with food may help your body absorb it slightly better and reduces the chance of stomach upset. There is no benefit to splitting doses throughout the day — your body absorbs what it needs and excretes the rest.

If you take a supplement, check whether it contains other ingredients. Some vitamin C products also include zinc, elderberry, or other substances marketed for immune support. Read the label to know what you are actually taking, and talk to your doctor or pharmacist if you take other medications, since some supplements can interact with them.

Who might need more vitamin C

Certain groups of people may have a harder time getting or keeping enough vitamin C. Smokers lose vitamin C faster and need 35 extra milligrams daily. People with limited access to fresh produce — due to cost, geography, or food insecurity — may benefit from a supplement. Older adults sometimes eat less overall and may fall short without planning.

People with certain medical conditions may also need more. Those with malabsorption disorders like Crohn's disease or celiac disease may not absorb vitamin C well from food. People recovering from surgery or serious illness may have higher needs while their body repairs itself. If you have a chronic health condition or take medications regularly, ask your doctor whether a vitamin C supplement makes sense for you.

Potential side effects and safety

For most people, vitamin C from food or normal supplement doses is safe. However, very high doses — typically above 2,000 milligrams daily — can cause side effects. The most common are diarrhea, nausea, and stomach cramps. These happen because excess vitamin C pulls water into your intestines.

People with certain conditions should be cautious about high-dose supplements. Those with a history of kidney stones should not take large amounts, because vitamin C is converted to oxalate in your body, and oxalate is a component of kidney stones. People with hemochromatosis (a condition where the body stores too much iron) should avoid high-dose vitamin C, because it increases iron absorption. If you have either of these conditions, talk to your doctor before taking a supplement.

Vitamin C supplements can also interact with some medications. If you take blood thinners, chemotherapy drugs, or certain other medications, high-dose vitamin C may interfere with how they work. This is another reason to mention any supplement to your doctor or pharmacist.

Frequently Asked Questions

Can I take too much vitamin C?

Your body excretes excess vitamin C in urine, so you cannot store it. However, doses above 2,000 milligrams daily can cause diarrhea and stomach upset. If you are taking a supplement, stick to the dose on the label unless your doctor recommends otherwise.

Is vitamin C from supplements the same as from food?

Chemically, yes — your body processes ascorbic acid the same way whether it comes from an orange or a tablet. Food provides vitamin C plus fiber, other nutrients, and compounds that work together. For most people, food is the better source if you can get enough that way.

Does vitamin C boost immunity?

Vitamin C supports normal immune function, and you need enough of it for your body to work properly. Taking extra amounts beyond your daily need does not make your immune system stronger. For most people, a regular source of vitamin C — from food or a modest supplement — is all that is needed.

What is the best time of day to take a vitamin C supplement?

There is no "best" time. Your body uses vitamin C throughout the day. Taking it with food may help absorption slightly and reduce stomach upset. Consistency matters more than timing — taking it the same way each day makes it easier to remember.

Can I get vitamin C from supplements if I do not eat many fruits and vegetables?

Yes, a supplement can cover your daily need. However, fruits and vegetables provide fiber, minerals, and other nutrients that a vitamin C supplement alone does not. A supplement fills a gap, but it is not a replacement for eating a variety of foods.