It’s easy to take your period for granted (or, you know, wish it away forever)—but when that time of the month rolls around and you’re surprisingly cramp-, rage-, and blood-free, you might start to wonder: Am I pregnant?
First: Take a beat—periods can go MIA for all kinds of reasons. Still, that doesn’t mean you should totally ignore your missed flow.
“If you have one or two irregular periods it is definitely something to pay attention to,” says Sherry Ross, M.D., an ob-gyn and women’s health expert at Providence Saint John’s Health Center in Santa Monica, California
Call your ob-gyn ASAP to suss out whether one of these factors may be to blame for your late period problems.
1. Major weight loss or excessive exercise
“We know excessive exercising, sudden weight changes and being underweight can offset your hormone levels,” says Ross. “One of these hormones is called leptin and is produced in fatty tissue. Excessive exercising and drastic weight changes can decrease the body fat causing this and other hormones (like estrogen) to drop, contributing to irregular periods.”
Rigorous exercising, such as training for a marathon or triathlon, can also cause physical stress, which may lead to a hormonal imbalance that screws with your period.
Significant stress—such as a divorce or death of a loved one—can disrupt your hormonal balance, creating delayed, irregular, and heavy periods, Ross says.
This is known as hypothalamic amenorrhea, says Alyssa Dweck, M.D., ob-gyn and co-author of V is for Vagina. “This particular area of the brain, the hypothalamus, is where a lot of the hormones for your period are regulated,” she says. “The hypothalamus is very affected by stress.”
3. Polycystic ovary syndrome (PCOS)
“The hallmark of PCOS is irregular periods, excessive hair growth in places you would rather not see it, multiple cysts on the ovaries seen on a pelvic ultrasound, and infertility,” she says. “Your hormones—estrogen and testosterone—are completely lopsided and irregular.” When you have PCOS, Ross says your periods can come every two weeks, every three to six months, or even just once a year.
4. Your birth control
“One of the side effects of a low-estrogen birth control pill is a light or non-existent period,” Ross says. “For many, this is a welcomed side effect.” The same goes for methods like hormonal IUDs, implants, or shots, since many of those don’t contain estrogen at all.
But if you’ve just stopped taking the pill, then take note: Ross says it might take one to three months to return to your normal cycle. Still, pay attention to what your period looks like when it finally comes back. “It may be once you are off the pill you may find you have an underlying hormonal problem that was masked by taking the birth control pill,” says Ross. If that’s the case for you, then it’s time to get in touch with your ob-gyn.
5. Thyroid dysfunction
The thyroid gland, located in your neck, regulates your metabolism, but it also interacts with many other systems in your body to keep things running smoothly. “If you’re dealing with any type of thyroid imbalance, whether it’s hypo- or hyperthyroidism, that can have implications for your period,” says Dweck.
Ross says other hormonal causes that could lead to irregular periods include Cushing’s disease, poor control of diabetes mellitus, premature ovarian failure, and congenital adrenal hyperplasia (a condition that limits hormone production in the adrenal glands).
If you took a pregnancy test and it showed you were pregnant, then your period (or something that looks like a period) arrived late and heavy, it could be a miscarriage, says Ross.
7. Certain medications
Whether you’ve been relying on certain OTC medications for an everyday headache or taking a prescription for a particular health issue, Ross says that some meds could be affecting your menstrual cycle. Aspirin, Coumadin (used to treat and prevent blood clots), and ibuprofen can all affect your cycle.
8. Premature menopause
When women under 40 have hormones misfiring in a significant way, they can go through premature menopause, also known as premature ovarian failure. Along with a missed period, signs of this condition include hot flashes, night sweats, and vaginal dryness.
But this shouldn’t be at the top of your list. “This isn’t very common, so you shouldn’t immediately worry about it,” says Dweck. If your ob-gyn rules out the many other potential causes for missed or late periods and thinks this may be the culprit, they’ll clue you in.