14 Reasons Why Your Period May Suddenly Be Shorter (& Why You Shouldn't Worry)

No two people have the same menstrual cycle. What's normal for one person may be completely abnormal for another. So, there's no such thing as a normal period. However, medical professionals do have some general guidelines that help them determine whether your menstrual cycle is typical or not.

A normal cycle is generally between 28 and 35 days. That means that the first day of your period is about 20 to 35 days after your last period. A normal period lasts for seven days or less, and the flow is consistent from month to month. Some people whose menstrual cycles fall within normal parameters occasionally spot between periods, but they don't regularly have mid-cycle bleeding.

To be considered normal, your period should be relatively consistent from month to month. What counts as "consistent" is completely dependent on your body and what's normal for you. Being a few days late or early isn't a big deal, and neither is a minor change in the length of your period or the heaviness of your flow. So, if you've noticed that your period is suddenly shorter — such as just a day or two long — you probably don't need to worry. Here are some of the (mostly normal!) reasons your period might be shorter than usual.

We all know that stress has a huge impact on our health. But did you know that stress can also change your menstrual cycle? In an article for GoodRx Health, Dr. Joanna Jan explains that being stressed for an extended period of time changes the body's hormone production because stress activates the "fight or flight response" in the nervous system. The body then produces extra cortisol, which is often called the stress hormone. Cortisol puts our bodies into a kind of survival mode, which helps the body respond to threats. When bodies with female reproductive organs are in that survival mode, the part of the brain that triggers the hormones that regulate the menstrual cycle may decide not to release those hormones. 

Back when early humans were constantly in danger, this response made sense. There shouldn't be any baby-making when your top priority is staying alive! These days, however, this response isn't so necessary. But our brains can't tell the difference between psychological stress and a legitimate threat. So whenever cortisol levels increase, the brain alters the menstrual cycle. Unfortunately, most of us are under pretty much constant psychological stress. And that stress can lead to irregular periods.

If you're suddenly having really short or light periods, check on your stress levels, and see what you can do to bring them down.

When people start to experience classic menopausal symptoms like hot flashes, mood swings, changes in sleep patterns, and vaginal dryness, they often assume that they've reached menopause. However, you're not actually in menopause until you've missed 12 periods in a row. These symptoms actually signal perimenopause, the transitional period leading up to menopause.

During perimenopause, the levels of estrogen in your body fluctuate each month. Over time, the ovaries release less and less estrogen, until they stop producing it completely. These changes in hormone levels have a noticeable impact on the menstrual cycle. Irregular periods become the norm rather than the exception. Often, people's periods get lighter and much shorter. Some people will only get their periods every few months instead of every month. For most people, this starts to happen in their 40s or even their 50s. Though it's uncommon, some people start to produce less estrogen in their 30s.

If your period is getting shorter in your 40s and 50s, there's a good chance you've started perimenopause so check in with your doctor to confirm. If you're in your 30s and your period is suddenly shorter, be on the lookout for other symptoms of perimenopause. If you believe your periods are getting shorter due to perimenopause, make an appointment with your doctor ASAP. Early perimenopause isn't necessarily bad, but your doctor may want to put you on hormone replacement therapy to counteract the symptoms.

If you've been trying to lose weight, you might be unintentionally screwing up your menstrual cycle. One study published in the medical journal "Gynecological Endocrinology" found that people who lost a significant amount of weight over a short period of time experienced noticeable changes in their menstrual cycles.

The study examined how the levels of several hormones associated with the menstrual cycle were impacted by weight loss. The study determined that moderate weight loss had little impact on the hormones responsible for the menstrual cycle. However, people who lost 20% or more of their body weight in a short period of time showed significant hormone imbalance and began having irregular periods. Some had shorter periods and some started to miss their periods altogether.

If you're currently losing weight on a diet, and you've experienced significant changes to your period, make an appointment with your doctor ASAP. Hormonal imbalances can lead to serious health issues.

The menstrual cycle is controlled by multiple hormones that get produced or released at different times throughout the cycle. When all these hormones are working properly, your period comes around the same time, lasts for about the same number of days each cycle, and your flow is relatively consistent with each cycle. But when one or more of these hormones isn't working the way it should, the changes to your menstrual cycle can be dramatic.

Most hormonal imbalances can be traced back to lifestyle factors: stress, lack of sleep, rapid weight loss, and excessive exercise. Or they may be caused by diseases or disorders, such as endometriosis, polycystic ovarian syndrome, or thyroid dysfunction. However, some people's bodies just don't produce or regulate hormones correctly for reasons that are difficult or impossible to identify. As Dr. Mary Stoffel, a women's health provider at Madison Women's Health, explains, when the body produces too much or too little estrogen, progesterone, and prolactin, your periods can become short, light, and irregular.

Diagnosing hormonal imbalances is tricky because hormones fluctuate so often. Your doctor will likely ask you to track your periods closely for a few months to see how your periods change with each cycle. Then they'll likely do a pelvic exam to check for structural problems that might be causing your irregular periods and perform multiple blood tests to check your hormone levels at different parts of your cycle.

Some people assigned female at birth produce more male hormones, called androgens, than they should. This happens due to underlying hormone imbalances that prevent these people from ovulating on a regular basis. When they don't ovulate, small cysts form on the ovaries, and these cysts release androgens. The increased levels of androgens disrupt the menstrual cycle even more.

This condition is called Polycystic Ovarian Syndrome (PCOS), named after the cysts that often develop. However, not everyone with PCOS develops cysts. Though doctors don't know exactly what causes PCOS, the consistent symptom is increased levels of androgens and irregular periods.

People with PCOS often have very light, short periods. Sometimes, they only get their period once every few months. Typically, people with PCOS have had irregular periods since their very first period. However, some people notice shifts in their periods when they're in their 20s or 30s. If your periods are suddenly shorter and lighter when they have been normal in the past, other causes are more likely than PCOS. But PCOS still could be behind the change, so it's a good idea to bring this up with your doctor.

When a person's ovaries start releasing less estrogen before age 40, they have a condition called Primary Ovarian Insufficiency (POI). This condition can begin as early as the teen years or as late as the early 30s.

If ovarian function decline happens when someone is in their late 30s, it could be early perimenopause or POI depending on the symptoms. With perimenopause, you'll miss several periods in a row until your period completely stops. With Primary Ovarian Insufficiency, you will skip periods, but your period may not completely disappear. Many people with POI still get periods, though typically not on a regular basis.

The other symptoms of POI are the same symptoms often associated with menopause: hot flashes, sleep disturbances, mood swings, brain fog, fatigue, and vaginal dryness. If your periods are suddenly shorter and you don't have any of these other symptoms, then you probably don't have POI. But continue to watch out for menopause-like symptoms. If you're younger than 40 and start to develop menopause-like symptoms in addition to a shorter period, check in with your doctor and have your hormone levels checked.

Another rare cause of shorter periods is hypopituitarism. This condition occurs when your pituitary gland doesn't make the hormones it's supposed to make or produces them in the wrong amounts.

The pituitary gland is responsible for four hormones that help regulate the menstrual cycle: Luteinizing hormone (LH), follicle-stimulating hormone (FSH), Thyroid-stimulating hormone (TSH), and Prolactin. If your pituitary gland doesn't make any of these hormones in the right amounts, you'll notice changes in your period. If your period is getting shorter and lighter, you probably have a Luteinizing hormone (LH) or follicle-stimulating hormone (FSH) deficiency, as these hormones are responsible for estrogen and egg production.

Hypopituitarism can be caused by a variety of underlying conditions including a tumor on the pituitary gland, inflammation of the pituitary gland, an infection in the brain, or any condition that causes a lack of blood flow to the pituitary gland. In the majority of cases, hypopituitarism will not be the reason for shorter, lighter periods. When all other potential causes have been ruled out, your doctor may suggest tests to assess your pituitary function and hormone levels.