8 Reasons Why Your Period Is So Bad

With painful periods, your one salvation is that they do, in fact, end relatively quickly. But, for people with heavy periods — which can last for over a week at a time — even that isn't necessarily the case.

"The biggest thing I notice is that women adjust to what is normal for them," says Timothy Ryntz, MD, a gynecologist at NewYork-Presbyterian Hospital. "Because these changes happen gradually over time, many people learn to adapt to what probably isn't a healthy amount of flow."

So what is and isn't healthy? It comes down to both the length and amount of your bleeding, Dr. Ryntz says, which can be kind of hard to keep track of. But the general rule of thumb is that, if you're bleeding for more than seven days or you're going through more than one pad or tampon per hour for a few hours, that's considered a "heavy" period. Some of us just naturally bleed more than others, but bleeding this much usually indicates that there's something else going on.

And that "something else" could be a lot of different things: Basically, anything that makes your endometrial lining thicker or interferes with the way it leaves your body will cause more bleeding. That includes anatomical issues (such as noncancerous tumors in your uterine lining), as well as medications, (such as progesterone-only birth control), which affect the hormones responsible for building up your lining.

Not all heavy periods are cause for concern, but there are some cases in which you're going to want to check in with your doctor. If you are bleeding for more than seven days (and especially if you've done so for at least three cycles in a row), it's time to call your doc. And if you have any symptoms of anemia — extreme fatigue, nausea, shortness of breath — along with heavy bleeding, get yourself some medical attention ASAP, Dr. Ryntz says.

Ahead, we've collected a few of the most common causes of heavy periods, and what you should know about 'em.