Let’s start with the important thing: Irregular periods can be totally normal. (Go ahead, breathe out that sigh of relief. We feel you.) If your period never shows up when you think it will — maybe you start bleeding a full week early, bleed more heavily than usual, or miss your period entirely — you’re definitely not alone. Irregular periods are surprisingly common. They can happen in about 30% of women in their “reproductive years,” a.k.a. the time during which you a) have your period, and b) are physically capable of getting pregnant.
Those reproductive years span your teenage years — or whenever you first get your period — to the wind-down of your menstrual cycle, which happens at pre-menopause in your mid-to late-40s. And it’s when things are starting up and winding down that you’re most likely to deal with irregular periods. Makes sense, since there’s a lot going on in your body that can throw off a schedule. Really, your body is just figuring out its new schedule, which can mean your period pops up early, late, or not at all.
How Long Do Periods Last?
Menstrual cycles are different for all of us, and the timeline is going to vary even once we are on a regular schedule. While the average length tends to be around 28 days, that’s definitely not the case for everyone — and it also isn’t the same exact timing every single month. Think of it as a monthly guessing game, the women’s health edition.
The exact time between bleeding can be anywhere from 21 to 35 days — it just depends on your body. Generally, your period is considered late when it comes after 35 days. If your period falls beyond this range more than once or twice, it can be a sign of something else going on. It’s a good idea to seek medical advice if your menstrual cycle is less than 21 days or longer than 35 — or if you experience other symptoms, such as heavy bleeding or pain. Your doctor can help you get to the bottom of it.
Tracking your period month after month can give you a better sense of how long your cycle is. It’s super simple: Just use our free period tracker to calculate when your next period is.
What Can Cause Irregular Periods
If you have an early period, a late period, or missed it altogether, that’s normal if you’ve only been getting your period for three or four months. After that, though, it could mean there’s something else going on. (We’ll get to that in a sec.) First, a mini-science lesson: Hormones are the boss of your reproductive system, controlling everything from ovulation (which is when your ovary releases an egg) to menstruation. They’re in charge of signaling to your body that the egg isn’t fertilized and therefore it’s time to shed the lining of the uterus, which makes up period blood. All this to say: If you have an irregular period, blame it on your hormones.
For when your hormones are out of whack or out of balance for any reason, it can do some weird things to your period — both the flow and its timing. That’s why irregular periods often happen in your teens or when you first start bleeding; your hormones are usually getting into their groove. Of course, there’s always the possibility with a missed period that you might be pregnant, in which case your body’s going to hang onto that uterine lining, or menopausal, in which you’re not ovulating at all. Besides that, some fairly common things can affect your hormones, in turn leading to irregular periods. A few of the usual suspects:
Dealing with a breakup, got a big event on the horizon, or straight-up drowning in work? That stress can cause irregular periods. When you’re in freak-out mode, your body sends out hormones to prep you for flight or fight — and it slows down non-essential functions, like those for your reproductive system, in the process and throws off your body’s usual timing. If you’re feeling frazzled 24/7, it could lead to a late period. Learn more about how stress can cause irregular periods.
2. Changes in your weight
If you lose or gain a ton of weight, it could throw a wrench in your body’s hormone balance. (Same goes if you’re restricting your calories.) Once that’s off-kilter, it can lead to a late or missed period.
3. Polycystic Ovary Syndrome, a.k.a. PCOS
PCOS is a health condition where your hormones are out of balance, which can cause irregular periods. As a result, you don’t ovulate regularly — and, no surprise, you therefore don’t get your period regularly, either. You might have a really heavy period, get irregular periods, or experience missed periods. And because it’s a hormone-based issue, it can have some rough symptoms, such as acne, excess hair on the face and body, weight gain, skin tags, and dark patches on the skin.
4. Birth Control
Some types of birth control work by manipulating your hormones. When you first start or stop taking hormonal birth control, you might have irregular periods as your body gets used to it. NBD.
How to Regulate Your Periods
There’s no way to make your period stick to a schedule outside of some types of birth control, which can take the reins from your hormones so you can plan or even skip your period. Otherwise, if your periods are still irregular after a few months and you’re not pregnant, make an appointment with your doctor. While most irregular periods resolve on their own, a women’s health specialist like an OB-GYN can diagnose something more serious, such as PCOS.