Key takeaways:
People often take vitamin C to prevent and treat cold symptoms, but the data is lacking on any real benefit.
If you take vitamin C on a regular basis, it may help to shorten the length of a cold when you get sick. But this effect is likely too small to notice a difference.
Although vitamin C may not help much with colds, it’s important to get enough of it every day. This promotes a healthy immune system.
During cold and flu season, people often turn to vitamin C (ascorbic acid) as a natural remedy for their symptoms. In fact, many over-the-counter (OTC) supplements for treating colds — like Airborne and Emergen-C — have high doses of vitamin C. These products claim to both prevent colds and help you get over them. But do they really work? Let’s look at what the research says.
Can vitamin C prevent a cold?
The current research consensus is that vitamin C doesn’t help prevent a cold. This is based on a large review of all the existing studies on vitamin C and cold prevention. Results showed that taking a daily dose of at least 200 mg of vitamin C wasn’t shown to decrease the likelihood of getting sick when exposed to a cold virus.
Commonly used OTC products like Emergen-C and Airborne have 1,000 mg of vitamin C per packet or tablet. But higher doses of vitamin C aren’t better at preventing you from getting an upper respiratory infection like a cold or flu either.
There may still be some use for daily vitamin C, though. It won’t keep you from getting sick. But it may help with colds once they have already started.
Can vitamin C help treat a cold once you’re sick?
Vitamin C might help to treat your cold. Research shows that regularly taking 1,000 mg to 2,000 mg of vitamin C per day may reduce how long cold symptoms last and how severe they are. But there are two important points about these findings:
This benefit is seen in people who take vitamin C every day, even before cold symptoms start.
The decrease in symptom duration and severity is small. So, it’s possible you won’t even notice the difference.
Another review study found that vitamin C may help with the severity of symptoms, too. It found that doses over 1 g per day helped a little bit with symptoms during the most “severe” phase of the cold. But again, this effect was small. And it didn’t seem to help with more mild symptoms.
When people take vitamin C after symptoms have started, the results have been mixed. There aren’t many studies that look at the effect on vitamin C after symptoms have started. And some show a benefit while others don’t.
In the studies that suggest vitamin C may help after you get sick, researchers note that it should be started within 24 hours of your symptoms arriving. Also, people should take it for at least 5 days.
Can zinc help get rid of a cold? There’s some evidence to suggest that zinc — more than vitamin C — can help you prevent and recover from a cold.
The best foods to eat when you have a cold: From chicken soup to ginger tea, we round up the science-backed foods that can help when you are sick.
Want to get rid of a cold fast? You don’t need to spend money at the pharmacy to get over a cold. You may already have these helpful home remedies on hand.
How can you treat the common cold?
There’s no cure for the common cold. And since it’s caused by a virus, antibiotics won’t help. But there are still a wide range of OTC treatments that can help reduce your symptoms as the infection runs its course. These include:
Decongestants, like pseudoephedrine (Sudafed) and phenylephrine (Afrin)
Pain and fever reducers, like acetaminophen (Tylenol) and ibuprofen (Advil, Motrin)
Nasal sprays, like cromolyn sodium and saline spray
Cough medicines, like guaifenesin and dextromethorphan
What’s vitamin C good for?
Even if vitamin C doesn’t help much with colds, it still plays an important role in your health. These are some of vitamin C’s benefits:
It helps protect cells from damage.
It helps your body absorb iron.
It keeps your immune system strong.
It helps with wound healing.
It helps produce collagen.
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Most people get enough vitamin C from their diets and don’t need OTC supplements. But some groups may be at an increased risk of low vitamin C levels. This includes people who:
Smoke
Have a restricted diet or limited food variety in their daily diet
Have certain chronic diseases, like digestive disorders and cancer
What’s the recommended daily dose of vitamin C when you’re sick?
The average dosage of vitamin C for colds is anywhere from 1,000 mg to 2,000 mg per day. But this is based on the dosage range in studies that looked at vitamin C for treating colds. These are much higher doses of vitamin C than you need each day.
The recommended daily intake for adults is:
Men: 90 mg a day
Women: 75 mg a per day
People who smoke: an extra 35 mg of vitamin C daily
It’s easy to meet your recommended intake with fruits and vegetables. For example, a medium orange has 70 mg of vitamin C. And a serving (½ cup) of sweet red pepper has 95 mg.
Can taking too much vitamin C have side effects?
Taking too much vitamin C can cause stomach upset. Vitamin C is safe for most people. But taking dosages higher than 2,000 mg per day may lead to symptoms like:
Nausea
Stomach cramps
Vitamin C can also have other effects in people with other medical conditions. For example, high doses may increase the risk of kidney stones in certain groups of people. And too much vitamin C may be dangerous for people who have hemochromatosis — a condition that leads to high iron levels in the body.
Vitamin C can also interact with some medications and supplements. Make sure to let your primary care provider know if you’re thinking about taking vitamin C supplements. They can let you know if vitamin C is safe for you to take.
What are good vitamins for a cold besides vitamin C?
There are many other supplements that people use to help with cold symptoms, but one with proven data is zinc. Studies show that zinc can shorten colds when someone takes it within 24 hours after symptoms start.
Research also shows that honey can reduce cough and congestion related to colds. This seems most effective in children with a nighttime cough. But it’s important to never give honey to children under 1 year old. It may cause a dangerous infection with botulism.
Other supplements — like echinacea, garlic, and elderberry — are also commonly used for colds. But the evidence is lacking on their effectiveness in treating or preventing colds.
Frequently asked questions
There are no head-to-head comparisons of zinc versus vitamin C for a cold. So it’s hard to say which one is better. But several studies suggest that zinc can help prevent, shorten, and lessen the symptoms of a cold. The evidence for vitamin C is less convincing.
Emergen-C contains many different ingredients that claim to help when you’re sick. As the name implies, vitamin C is one of the main ingredients. But the research doesn’t suggest extra vitamin C will have much of an impact on your cold — even at very high doses like in Emergen-C.
There are many different vitamins and minerals that play an important role in keeping your immune system strong. Examples include:
Vitamin B
Vitamin C
Vitamin D
Folate
Iron
Magnesium
Zinc
Most people get enough of these nutrients through their regular diet. And they don’t have severe enough deficiencies to cause a weak immune system.
If you have any chronic medical conditions and are concerned that you keep getting colds, it’s important to raise this concern with your primary care provider. They can help you figure out if you’re at risk for a deficiency and test your levels, if needed.
According to the available research, vitamin D is unlikely to help you get over a cold. There’s some evidence that people who are low in vitamin D are more likely to catch a cold. So vitamin D supplements for these people may help prevent them from getting sick. But vitamin D won’t cure a cold.
There are no head-to-head comparisons of zinc versus vitamin C for a cold. So it’s hard to say which one is better. But several studies suggest that zinc can help prevent, shorten, and lessen the symptoms of a cold. The evidence for vitamin C is less convincing.
Emergen-C contains many different ingredients that claim to help when you’re sick. As the name implies, vitamin C is one of the main ingredients. But the research doesn’t suggest extra vitamin C will have much of an impact on your cold — even at very high doses like in Emergen-C.
There are many different vitamins and minerals that play an important role in keeping your immune system strong. Examples include:
Vitamin B
Vitamin C
Vitamin D
Folate
Iron
Magnesium
Zinc
Most people get enough of these nutrients through their regular diet. And they don’t have severe enough deficiencies to cause a weak immune system.
If you have any chronic medical conditions and are concerned that you keep getting colds, it’s important to raise this concern with your primary care provider. They can help you figure out if you’re at risk for a deficiency and test your levels, if needed.
According to the available research, vitamin D is unlikely to help you get over a cold. There’s some evidence that people who are low in vitamin D are more likely to catch a cold. So vitamin D supplements for these people may help prevent them from getting sick. But vitamin D won’t cure a cold.
The bottom line
People often use vitamin C to treat and prevent colds. While the data is mixed, taking vitamin C regularly doesn’t seem to help very much in keeping people from getting sick. It also doesn’t significantly shorten the time they’re sick. But vitamin C probably won’t harm you if you take it at the recommended dosages. Make sure to talk with your healthcare team first, as vitamin C can interact with some medications and supplements.
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References
Bucher, A., et al. (2016). Vitamin C in the prevention and treatment of the common cold. American Journal of Lifestyle Medicine.
Ferraro, P. M., et al. (2015). Total, dietary, and supplemental vitamin C intake and risk of incident kidney stones. American Journal of Kidney Diseases.
Hemilä, H., et al. (2013). Vitamin C for preventing and treating the common cold. The Cochrane Database of Systematic Reviews.
Hemilä, H., et al. (2023). Vitamin C reduces the severity of common colds: A meta-analysis. BMC Public Health.
InformedHealth.org. (2023). Common colds: Does vitamin C keep you healthy? Institute for Quality and Efficiency in Health Care.
MedlinePlus. (2024). Vitamin C and colds.
NCCIH Clinical Digest. (2020). The common cold and complementary health approaches. National Center for Complementary and Integrative Health.
Office of Dietary Supplements. (2025). Dietary supplements for immune function and infectious diseases: Fact sheet for health professionals. National Institutes of Health.
Office of Dietary Supplements. (2025). Vitamin C: Fact sheet for health professionals. National Institutes of Health.
