For a long time, menstruation was treated as something shameful or unpleasant that needed to be hidden away, instead of as the amazing roadmap to your health that it can be. Luckily, that attitude is changing, and many in the gynecological world now view your period as a “vital sign,” Alyssa Dweck, MD and assistant clinical professor in the department of obstetrics, gynecology, and reproductive science at the Mount Sinai School of Medicine, says.

Indeed, your period can go far beyond simply telling you if you’re pregnant or not, which is why knowing your cycle is so important. What’s normal for you might not be normal for someone else, but if you’re attuned to what your period typically looks and feels like, you’ll be able to spot any changes immediately. Here, Dr. Dweck and Felice Gersh, MD, medical director of the Integrative Medical Group of Irvine, share five changes to watch out for, what they might mean, and when to see your doctor.

If your period blood is light pinkish in color, you could have: low estrogen levels. Your estrogen levels decline as you age, but if you’re under the age of 40 and regularly experience light pink, spotty periods, vaginal dryness, fatigue, or painful sex, it may be worth it to get checked out by your doctor. You might also want to check the labels of any prescription drugs you’re on, as certain medications (such as anti-seizure meds) can alter estrogen levels, says Dr. Gersh. If you’ve recently started taking a new medication and notice significant changes to your period, call your doctor and see if you can switch to a different medication or start an alternative treatment plan.

If your period is heavy, painful, AND lasts longer than seven days, you could have: endometriosis, uterine fibroids, polyps, or pelvic inflammatory disease, according to Dr. Gersh. All of these conditions are treatable (though there’s no cure for endometriosis), but they can all cause serious problems, including infertility, if left untreated. If you experience any of the above-mentioned symptoms — other common symptoms can also include pain and bleeding during or after sex or regularly bleeding through your pad in less than an hour — it’s imperative that you speak to your doctor about them.

Keep in mind that changing birth control methods can also throw your period off. For example, it’s not uncommon for women who change from the pill to the copper Paragard IUD to experience heavy bleeding for the first six months to a year, Dr. Dweck says. On the other hand, if you’ve used the same form of birth control for years and are suddenly experiencing heavy bleeding or more pain, it’s likely something else is responsible for your symptoms.

If your period is irregular or you often skip periods, you could have: Polycystic ovarian syndrome (PCOS), especially if your symptoms are accompanied by cystic acne on your chin or jawline, difficulty losing weight, or excess hair growth, Dr. Dweck says. If you suspect PCOS could be the root of your period problems, call your doctor and ask them to do an ultrasound to confirm. Not every single woman with PCOS will have cysts on her ovaries, but most do. While there’s no cure for PCOS, it’s often treated with birth control pills or Spironolactone.

Dr. Dweck says another culprit could be your thyroid. Your thyroid plays a crucial role in hormone production, so if your hormones are out of balance, there’s a good chance your period will be, too. If you notice your periods are suddenly lighter, shorter, and farther apart, hyperthyroidism could be to blame. In contrast, hypothyroidism can cause heavier periods that are longer than usual.

And, again, your birth control can also throw your cycle out of whack: women with a hormonal IUD might find their period to be really irregular the first three to six months, and many women who get the Depo-Provera shot stop getting their periods altogether.

If you regularly experience severe cramping, you could have: low magnesium levels. Because the standard American diet tends to be high in sugar, fat (especially from corn-fed animals), and carbs, it’s possible that you’re not getting enough antioxidants, vitamins, or minerals, suggests Dr. Gersh. “Magnesium is very important when it comes to muscle function, and because the uterus is a muscle, women often experience cramping because they don’t get enough magnesium from their diet,” she says. Try increasing your intake of leafy green vegetables, fish, sunflower seeds, avocados, and bananas for a few months and see if that makes a difference in your pain levels.

If your period is completely absent, you could have: stopped ovulating, especially if you’ve missed three or more periods. A few things can cause this, including extreme exercise, Dr. Dweck says. While this is more common among top endurance athletes, it can happen to you too, especially if you’ve added weight-lifting to your routine or have taken up a strenuous routine after months of not working out, for example. The good news is that this should be temporary, and once your body gets used to your new routine, your period should come back within a couple of cycles. Plus, research shows that moderate exercise might actually improve the headaches, cramping, nausea, and back pain that many women experience while on their periods, so don’t be afraid to keep working out — just be careful not to overdo it.

Another more serious possibility is that of an eating disorder. “Very restrictive diets can cause a decrease in your BMI, and once you get below a certain point, you stop ovulating,” Dr. Dweck says. “It’s nature’s way of preventing you from getting pregnant if you’re starving.” If you’re struggling with an eating disorder or know someone who might be, reach out to the National Eating Disorders Association for help.

Intense changes in your diet can also mess with your cycle, though this tends to be temporary. “We sometimes see this in kids who go to college and change their eating habits and activity levels,” Dr. Dweck says. Even if you’ve left your college days far behind, it may be worth looking at your diet. Are you eating enough protein? Consuming too little protein can throw your body’s estrogen and insulin levels off, which can cause you to — you guessed it — miss your period.

“Your period should be predictable,” Dr. Gersh says. “It shouldn’t disrupt your life.” If you consistently find that your period negatively affects your quality of life, that’s a sign that something is amiss and shouldn’t be ignored.

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.