During cold and flu season, there’s a lot to deal with: remembering to get your flu shot, making sure you clean your hands and cover your mouth when you sneeze so as not to spread germs — the list goes on. Which means that thinking about your menstrual cycle might fall by the wayside. But research has shown that the flu can affect your period in ways you might not expect. It might seem odd that an illness that doesn’t seem to have anything to do with reproduction can throw a period out of whack — but menstrual cycles are affected by many different factors, and it turns out that viral infections are one of them.
The common cold, which is usually resolved in a short period and confines itself to the respiratory system, shouldn’t do anything to your menstrual cycle at all. It’s a different story with the flu, though. Menstrual cycles can be disarranged by the flu because of the illness’s severe impact on the body’s immune system and resources — to the point that periods can be delayed or even missed altogether while you’re down with serious flu symptoms.
The reason behind this involves the menstrual cycle’s key purpose: getting the body ready for potential pregnancy, and then flushing out the reproductive system when a fertilized egg isn’t implanted. “A flu with high fever for a few days or lots of vomiting and diarrhea can make your body think that you aren’t well enough to get pregnant,” pediatrician Dr. Molly O’Shea writes for Kotex. “So your body might delay or prevent ovulation for that cycle.”
It’s also worth noting that during your menstrual cycle, temperature tracking can also be thrown off by flus. Fevers and high temperatures can interfere with your basal body temperature, which is used by fertility apps to measure ovulation. If you get sick during your period and are used to tracking fertility using a temperature app, it’s important to remember that it may not be accurate while you’re experiencing flu symptoms.
The flu can also enhance your risk of dehydration when you’re on your period. If you have a fever, you sweat out a lot of fluid, and that can bring the body into a dehydrated state. You’re already at higher risk of dehydration when you menstruate because your estrogen levels plateau, causing your body to retain less water. So if you have your period during a bout of flu, it’s absolutely crucial to keep your fluid levels up, as you’re more vulnerable to dehydration. (Also, I’m so sorry.) Dehydration can make period cramps worse, too, so flu can coincide with a lot more abdominal aching during your period, too.
While these are potential ways having the flu can mess with your period, it’s important to note that this is different from “period flu,” a collection of flu-like symptoms, including nausea and achiness, that can occur in response to the hormonal shifts just before a period. Period flu is caused by declines in estrogen before menstruation, and while it’s not pleasant, it’s not actually true influenza.
If you want to avoid having the flu impact your period, the solution is simple: get your flu shot. While the shot might not protect against all strains of the virus going around this year, research has shown that if you get the flu after getting the shot, the illness is likely to be far less severe. Getting your flu shot is important for other reasons, such as contributing to herd immunity and protecting people who, for health reasons, aren’t able to get their shots themselves.
Getting your period when you have the flu might seem like your body’s deliberately deciding to make your day worse. If you happen to miss your period because you’ve down with flu, though, it’s likely not a signal that something is irreparably wrong; your body is just postponing things till you get better. Talk to your OBGYN if your cycle isn’t back to normal in about a month, but otherwise, rest up, drink lots of fluids, and hang in there; the flu normally runs its course in about a week or two.