Sniffles, sneezes, and an achy head are a good indicator that you’ve caught a cold—and nobody wants to be sick during the holidays. But megadoses of vitamin C won’t make your illness magically disappear. In fact, it could add to your woes.

“Once you've come down with symptoms, nothing, including vitamin C, can significantly shorten the course of a common cold, which usually lasts 7 to 10 days,” says Marvin M. Lipman, M.D., Consumer Reports' chief medical adviser. Here are five reasons vitamin C is not much better than a tincture of time.

1. It’s Probably Too Late

People who regularly take supplemental doses of vitamin C may recover slightly faster from the common cold than others, according to a 2013 review of 31 studies including nearly 10,000 individuals. But those people are no less likely to get sick in the first place, the review found. And taking high doses of vitamin C once you start feeling cold symptoms won't help you recover any faster, either, the researchers found.

2. You Might Get Kidney Stones

Men who regularly take vitamin C are twice as likely to develop kidney stones. That’s according to an 11-year study of 48,850 Swedish men. Over the course of the study 436 reported developing kidney stones.  

3. Your Body Will Just Eliminate It Anyway

Your body won't benefit from high doses, anyway. That's because any vitamin C that your body can’t absorb will be excreted in your urine. According to the National Institutes of Health (NIH), adult women only need 75 milligrams (mg) and adult men need 90 mg per day—and you’ll get more than enough in one large orange or a cup of strawberries

4. It Could Give You Diarrhea

The maximum that adults should ingest is 2,000 mg, according to the NIH. Any more and you could end up with nasty stomach cramps and diarrhea in addition to your runny nose and headache.

5. It's Not Worth the Money

Save the cash for tissues and tea and maybe a new fever thermometer and a humidifier. You’ll feel better in a week or so anyway.