How much vitamin C to slay your sniffles?

Vitamin C is best known for its ability to fight viruses — especially the common cold.

Of course, some people will tell you vitamin C’s cold-fighting abilities are a myth. But, the truth is, its cold-fighting reputation is warranted…

Studies show that if you take vitamin C before catching a cold it can reduce the severity of your symptoms. And, if you take it after catching a cold, it can shorten the duration of your cold. But here’s the catch…

Most clinical trials show that vitamin C only reduces the duration of your cold by a mere 10 percent. That means, if you have a cold that would typically last 10 days, vitamin C can knock the time you spend sneezing and sniffling down to nine days.

Now, one less day spent feeling sick and miserable is worth the minimal effort required to take a daily vitamin C pill. But it does make you wonder whether vitamin C is the miracle cure for colds that we’ve hoped for all these years…

I, for one, know there have been times when I’ve taken vitamin C at the first signs of a cold and it’s gone in a day or two max.  And I’m sure you’ve probably had experiences like this too. So why do these anecdotal experiences defy the clinical evidence?

Well, it may be due to dosage….

The more C, the better

Most clinical trials studying the effect of vitamin C on colds give participants modest doses of the vitamin. Typically, it’s about 1 gram (1,000 mg) per day. But, interestingly enough, trials that use a dosage higher than 1 gram end up with better results…

That’s why researchers from the University of Helsinki in Finland decided to take a closer look at two randomized trials that compared the effects of varying doses of vitamin C on the common cold.

The first trial they analyzed compared the effect of 3 grams of vitamin C per day with the effect of 6 grams per day. It turns out, 6 grams of vitamin C per day shortens the duration of colds by twice as much as 3 grams per day. People who took the 6 grams recovered 17 percent quicker than those who didn’t take any.

The second study they analyzed had similar findings. This time researchers compared the effect of 4 grams of vitamin C per day with the effect of 8 grams per day. Once again, a double dose had double the effectiveness. People who took 8 grams shortened the length of their cold by 19 percent.

Basically, these studies show there is a dose-response relationship between vitamin C and colds—the more you take, the better the results. That means doses exceeding 8 grams per day could fight colds even more powerfully. But there’s no way to know for sure until more research is done. In the meantime, researchers say 8 grams should be plenty to help you see significant improvement in your cold.

“Given the consistent effect of vitamin C on the duration of colds, and its safety and low cost, it would be worthwhile for individual common cold patients to test whether therapeutic 8 g/day vitamin C is beneficial for them. Self-dosing of vitamin C must be started as soon as possible after the onset of common cold symptoms to be most effective,” said the researcher who performed the analysis Dr. Harri Hemilä from the University of Helsinki.

If you’re planning on upping your dose of vitamin C next time you get a cold, I have one word of warning for you…

Taking vitamin C in such high doses is unlikely to put your health in any serious danger (Linus Pauling took 18,000 mg of vitamin C per day and lived to be 93), but it can cause diarrhea, nausea and (in rare cases) kidney stones.

If you’re looking for another vitamin cure to make your colds less miserable and less frequent, you may want to check out the cold-busting powers of the sunshine vitamin — vitamin D — too.

Editor’s note: Did you know vitamin C is a powerful cancer killer? It’s just one of dozens of natural ways to survive and avoid cancer the mainstream medical community would rather you never knew. Click here for a preview of Dr. Michael Cutler’s comprehensive guide, Surviving Cancer!


  1. Do home remedies for the common cold really work? — MedicalXpress. Retrieved April 18, 2017.
  2. Larger doses of vitamin C may lead to a greater reduction in common cold duration — MedicalXpress. Retrieved April 18, 2017.
  3. Vitamin C and Infections — Nutrients, 2017.
  4. Overloading On Vitamin C? — Retrieved April 18, 2017.
Jenny Smiechowski

By Jenny Smiechowski

Jenny Smiechowski is a Chicago-based freelance writer who specializes in health, nutrition and the environment. Her work has appeared in online and print publications like Chicagoland Gardening magazine, Organic Lifestyle Magazine, BetterLife Magazine,, and