FYI, the scientific term for abnormally low bleeding is hypomenorrhea. While most periods produce between 30 to 50 mL, a person with hypomenorrhea is producing substantially less than 30 mL per cycle, according to the book Clinical Methods: The History, Physical, and Laboratory Examinations. It's pretty difficult to measure out your period in mL, but this is just a point of reference.
Lina Akopians, MD, PhD, a specialist in reproductive endocrinology at the Southern California Reproductive Center, says that a period that lightens up substantially could be caused by a hormonal issue or a structural one (meaning something happened to an organ in your body). Here are 8 reasons that might explain why your flow is so light.
Admit it: You've watched at least one episode of the TLC series, I Didn't Know I Was Pregnant, and you probably thought the women were crazy. How could someone grow a baby for 9 months and not have a clue?
While we can't explain why they didn't notice that their bellies were getting rounder, some about-to-be-mums remain in the dark for pretty long simply because they've been taught that as long as they're getting periods, there's no way they could be pregnant. Turns out, that's wrong.
Although most women stop getting periods once they conceive, some continue to experience bleeding, says fertility expert Janet Choi, MD, medical director at CCRM in New York. In fact, she's had patients who've been struggling to get pregnant go out drinking after a light version of their period shows up—only to later learn that they really are with child.
Unusually light periods or spotting could also indicate an ectopic pregnancy (when an egg implants somewhere other than the uterus), which can be very dangerous. When in doubt, take a pregnancy test.
You've lost or gained a ton of weight
Despite being capable of carrying another human being to term, your body's chemistry is really quite delicate, and when you add or subtract a bunch of poundage from it, it can freak out. One of the ways that manifests is by denying you your monthly visit from Auntie Flow, or by making those visits a lot shorter or lighter. While this may seem like a positive, Akopians notes that "your body needs a healthy balance between protein, carbohydrates, fats, and vitamins" if you want it to keep operating normally.
You're stressed to the max
While the usual day-to-day annoyances like having a fight with your spouse or blowing a presentation at work aren't enough to throw your hormones out of whack, Choi says that major life stressors—for example, your parents dying—can do just that. She also points out that over-exercising can also wreak havoc on your period because of the stress it puts on your body, physically.