How Many Weeks Pass Between Menstrual Periods?

Here's why, in general, you shouldn't be alarmed if your periods don't show up every 28 days.

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Every woman is unique and her period is unique too. Having your periods more than every four weeks is not bad. If your periods don't show up every 28 days, it may not be a cause for worry.

The Office on Women's Health (OWH) stated that "[r]egular menstrual periods in the years between puberty and menopause are usually a sign that your body is working normally." The keyword here is "regular," meaning if your periods are coming when you expect them, you shouldn't be too concerned.

What Factors Play A Role in Having Regular Periods?

Periods are different for every person, according to the OWH. The sweet spot of four weeks is an approximation. However, anything between 24 and 38 days is considered normal. It's also fine if your cycles vary by a few days (e.g., they average 31 days apart, but in some months, there's a 24- or 38-day gap).

Per the OWH, your age also affects how your period is regulated. For younger individuals, it can take up to three years for a menstrual cycle to fall less than every 38 days. By the time you reach your 20s and 30s, your period is mostly regular unless you have been diagnosed with a health condition or are experiencing changes that may affect your period timing. By the time you reach perimenopause, or the time of transition to menopause later in life, it is to be expected that your period will be irregular.

Longer Cycles and Fertility

Many people with long cycles worry about their fertility. Ovulation—when an ovary releases an egg—plays a role in fertility. The timing of ovulation can vary during the menstrual cycle. "Each woman's cycle length may be different, and the time between ovulation and when the next period starts can be anywhere from one week (7 days) to more than 2 weeks (19 days)," the OWH stated.

Regardless, many individuals with longer or irregular cycles get pregnant without a problem. Medications that stimulate ovulation, like clomiphene (also known as Clomid), may help if you're trying to conceive.

What if Your Periods Are Irregular?

You should pay more attention if your periods become irregular—in other words if they're unpredictable. Also, periods that come more than 38 days apart could be a symptom of a more serious problem. One issue could be hypothyroidism, a sluggish thyroid gland. Your healthcare provider can run blood tests to check your thyroid levels and prescribe medicine to help.

They will also want to rule out polycystic ovary syndrome (PCOS). Infrequent periods are a common symptom of PCOS due to a lack of ovulation caused by hormonal changes. Birth control pills (or the patch or ring) can restore order to your cycle by regulating hormones.

According to the National Institute of Child Health and Human Development (NICHD), other possible conditions or factors that can cause period irregularity include:

  • Pelvic inflammatory disease (PID)
  • Eating disorders
  • Stress
  • Uncontrolled diabetes
  • Excessive exercise
  • Obesity
  • Primary ovarian insufficiency (POI)

Furthermore, if your period is followed by more bleeding within three weeks, that can be a sign of an infection, fibroids, or, much more rarely, a cancerous tumor. Your healthcare provider will likely send you for an ultrasound to figure out what's going on.

Ultimately, don't wait to seek medical care if you find that anything is abnormal when it comes to your menstrual cycle. Your healthcare provider will be able to help you determine if what you're going through is out of the ordinary or just a normal part of menstruation for sure.

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