How Late Can a Period Be? Causes of a Late Period and When to See a Doctor

Menstrual cycles and periods can be unpredictable. Whatever your normal, you’ve probably experienced a few late periods.

Maybe your cycle is generally irregular and your period is often late. Maybe your period usually comes right when you expect it, but it’s late this time around. Either way, if you’re counting the days since your last time of the month and wondering just how late can a period be, we have the answers for you. 

Here’s what you need to know about how much menstrual cycles vary, how late a period can be, the causes of late menstrual period, and when to see a doctor about a late period.

How much do menstrual cycles vary?

If your calendar or period app says you should have gotten your period already, it’s only natural to wonder what’s going on. Cycle variability can help you understand how much your cycle length may change from month to month—which impacts how late your period can be.

A menstrual cycle that lasts between 21 and 35 days on average is considered to be regular. Average cycle length may be pretty reliable if you have a regular cycle, meaning (generally speaking) your period comes around the day you expect it. 

However, not everyone has regular cycles, and even those who do can experience changes in cycle length from one cycle to the next. 

In fact, cycles can vary quite a bit. As many as one in three people may experience irregular cycles at some point during their reproductive years. A little over one in ten people (13.5%) may have longer-than-usual cycles—aka late periods—on a regular basis. 

Age can also affect cycle variability. Demographic data shows that people aged 24 to 34, plus those 45 and older, may be more likely to experience late periods than people aged 35 to 39. On average, cycle length may vary by four or five days each cycle in these younger and older age ranges. But cycle length can even vary in the more stable 35-to-39 age bracket—potentially by three or four days.

How late can a period be?

Now, flash back to you, counting off the days since your last period. How does cycle length and variability relate to you and your late period? And how late can a period be?

Like so much that has to do with bodies and menstrual cycles, the answer to that question is: it depends on you. How late your period can be varies depending on your age, what your menstrual cycle is usually like, and what’s making your period late. Plus, since cycle length can vary, your period may have some wiggle room.

So, what is considered a late period? If your cycle is regular, your period will generally start within 21 to 35 days of your last period. If it’s been more than 35 days, your period is considered late.

Your period can also be considered late sooner than that, though, depending on your version of normal:

• If your cycle is normally really regular—like, accurate period predictions nearly to the day—and you’re at least three days due, your period can be considered late. 
• If your cycle length varies or tends more toward irregular, your period may be more accurately considered late once it’s at least a week past due. 

Just how late your period can be before it means something’s up is a waiting game. You have to wait and see if your period comes late or doesn’t come at all, then determine next steps. 

How late can a period be before it’s considered missed? 

Generally, a period can be considered missed or skipped if it’s been over six weeks since your last period. (You can take a pregnancy test well before that, though.)

If it’s been at least three months since your last period but you’re not pregnant, you may be experiencing amenorrhea, or the absence of periods. Amenorrhea is frequently a sign of an underlying health condition. Consider making an appointment with your doctor to find the cause of your missed periods and determine treatment.

Why is my period late?

There are lots of different reasons why your period could be late:

• You’re experiencing a fluke cycle
• Your cycle is going through a period of irregularity due to factors like stress, travel, grief, diet changes, weight fluctuations, or overexercise
• You recently started, changed, or stopped hormonal birth control
• You’re breastfeeding
• You’re in perimenopause
• You have an underlying health condition
• You’re pregnant

If your period is a couple days to a week or so late, it isn’t necessarily cause for concern, particularly if that only happens every once in a while. In many cases, you don’t have to do anything about a late period. 

If there’s a chance you could be pregnant, consider taking a pregnancy test about a week after the day you expected your period to come. If you have irregular cycles, try testing at least 36 days from the start of your last period.

Should I talk to my doctor about my late periods?

Sometimes your period is late and there’s no particular reason—that can happen from time to time.

In some cases, though, late periods could be related to an underlying health condition such as polycystic ovary syndrome (PCOS), endometriosis, pelvic inflammatory disease (PID), thyroid conditions, or ovarian cysts.

Consider talking to your doctor if:

• Your period is unusually late in multiple cycles
• You suddenly experience shorter or longer cycles
• You suddenly experience a much heavier or lighter flow
• Your period is suddenly longer or shorter
• You frequently experience spotting between periods
• You skip a period (or multiple), but you’re not pregnant

These scenarios don’t necessarily mean something’s wrong, but it’s a good idea to check in with a healthcare professional and make sure.

How late can a period be: the bottom line

How late your period can be depends on your body and your cycle.

Generally speaking, your period can be considered late if it’s been more than 35 days since your last period, if your cycles are regular and your period is three days due, or if your cycles are irregular and your period is seven days due.

Periods can be late for lots of reasons, including hormonal birth control use, breastfeeding, perimenopause, pregnancy, or a simple fluke cycle.

If you have questions about late periods, or if you experience sudden and frequent changes or irregularities in your menstrual cycle, consider talking to your doctor to figure out what could be going on.

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