Your 20s are an exciting, crazy, constantly changing time (new cities! new jobs! new relationships!), but they’re also a great opportunity to start healthy lifestyle habits now — while you’re basically at your physical peak — to make staying healthier later in life easier. One simple way to do that? Pay attention to your period.

Your period is considered a “vital sign,” meaning it’s a road map to your overall health and can tell you all kinds of important things about your body (maybe you’re in perfect health; maybe you need to kick up your feet and schedule a little R&R). Here are five things to know about your period during your twenties.

Your period should be pretty regular by now
For the first couple of years after you start your period, it’s not uncommon to be somewhat irregular. But by the time you hit your early 20s, your hormones should have stabilized a bit, meaning your period should be more predictable. In fact, many women find that they can pinpoint down to the day and time exactly when their period will start. Still, if your period is late every once in a while, don’t sweat it. “Even a woman whose period comes like clockwork will occasionally have a cycle that varies,” says Angela Dempsey, an OB-GYN at the Medical University of South Carolina, in an interview with Real Simple.

But your cramps might be worse
Mother Nature has a weird sense of humor: your hormones may have stabilized, but your prostaglandins — the group of hormones that are produced by your endometrial lining and, oh yeah, are responsible for your period cramps — are at peak production. That means your cramps might feel worse than ever, explains David Plourd, M.D., an assistant professor of obstetrics and gynecology at the Naval Medical Center in San Francisco, to Shape.

Stress can take a toll
Because your 20s tend to be a time when you’re running in five directions all at once, 20-something women report being S-T-R-E-S-S-E-D out. SELF reports that stress can cause what’s called anovulation, which is when your body doesn’t release an egg every month, leading to late or missed periods.

And so can birth control
Birth control prevents pregnancy by preventing ovulation — the process by which your ovaries release an egg into your fallopian tubes every month — but it can also cause lighter periods.

While there’s no evidence that it’s harmful to be on the pill long-term, going on and off of it or switching methods (from the pill to an IUD, for example) can cause temporary changes, such as heavier periods, irregular periods, or severe cramps. The good news is these changes are temporary and should subside as your body gets used to its new normal.

This is also when polycystic ovarian syndrome rears its head
If your period is suddenly erratic or MIA for at least three months in a row, and you’ve ruled out other potential causes — stress, pregnancy, your birth control — it could be polycystic ovarian syndrome, or PCOS. According to Redbook, PCOS tends to show up more often in 20-something women, though experts aren’t entirely sure why.

So while your 20s can feel like an insane roller coaster that you didn’t ask to be on, knowing yourself and your body can go a long way in making that ride feel much smoother.

Alanna is a freelance writer and editor living in Brooklyn. She's written for Shape, Fitness, Cosmopolitan, Reader's Digest, Vivala.com, and more, and mostly spends her time now searching for the perfect coffee shop, writing about all things health and wellness, taking photos of her dog, and trying (and failing) to become a dedicated runner. Follow her on Twitter or Instagram.