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.


Hormonal birth control use

When you start taking hormonal birth control or switch the type you're taking, your period can change. Anna Druet, the former Science and Education Manager for Clue, explains that the hormones in birth control get released into your body, ensuring that you have a consistent level throughout your cycle. If you're taking the pill, then you can choose to take a week of placebo pills so you can have your period.


However, this isn't actually a period! It's called withdrawal bleeding and it happens because your hormone levels shift when you're taking the placebo pills. Withdrawal bleeding isn't the same as actual menstrual bleeding, so your period will probably be shorter and lighter. Some people totally stop getting their periods while on hormonal birth control, especially people who choose continuous methods like a hormonal IUD.

So, if your period suddenly gets shorter a cycle or two after you start taking hormonal birth control or switch birth control methods, then it's nothing to worry about at all. Enjoy the more manageable periods!


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.


It's completely normal for your periods to change as you get older. Even if you've been able to predict the arrival and departure of Aunt Flo with alarming accuracy for years, things will change as you get into your 30s and 40s. Dr. Karmon James, an OB/GYN with Cleveland Clinic, says that as people who are assigned female at birth (AFAB) age, their ovaries gradually produce less estrogen, which leads to changes in the menstrual cycle. This process is known as perimenopause.


If you're in your 20s or even your 30s, it's pretty unlikely that a shorter period is related to your age. It's much more likely that it's related to pregnancy or breastfeeding if you've given birth, hormonal birth control if you're taking it, or lifestyle factors. But if you're in your 40s, or even late 30s, and your period is suddenly getting shorter, it could just be a normal part of getting older.


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.


Sleep deprivation

You've probably heard countless times how important sleep is for your physical, mental, and emotional well-being. And you might be tired of hearing about it, especially if you know you're not spending enough time in bed, and getting more shut-eye seems impossible. But we have to talk about the importance of sleep again because sleep can have a major impact on your menstrual cycle. 


Sleep helps to regulate two hormones that are essential to the menstrual cycle.One of those hormones is cortisol, the stress hormone. Sleep helps bring cortisol levels down. When we don't get enough sleep and we're constantly stressed, cortisol levels never have a chance to completely drop. And eventually, this alters the menstrual cycle.

Sleep also plays a major role in regulating melatonin. If you've heard of melatonin before, you probably know that it helps manage your sleep cycles. But melatonin is also responsible for triggering the start of your menstrual cycle, and regulating how long your period lasts. When melatonin production is disrupted by a lack of sleep, your body struggles to regulate your period.


Issues with cortisol and melatonin production caused by lack of sleep can both contribute to shorter, irregular periods. So, if your periods have changed lately, try getting some more sleep.

Rapid weight loss

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.

Excessive exercise

We've all heard that it's possible to do too much of a good thing, and believe it or not, that applies to exercise. Overexercising can lead to multiple health problems, including irregular periods.

Exercise puts stress on the body, and long-term stress can alter the menstrual cycle. Working out also requires a lot of the body's energy. When too much of its energy is being used for exercise, the body compensates by taking energy from other bodily processes. Basically, the brain tells the body that there's not enough energy available for a normal menstrual cycle, so periods get shorter and lighter or disappear altogether. The same thing can happen when a person's body fat percentage gets really low. This puts the body into starvation mode. When in this mode, the body shuts down all unessential bodily processes, including the menstrual cycle.


Even people who aren't dieting and eat a balanced diet can end up in starvation mode if they're exercising too much. Any time the amount of energy we expend exercising far exceeds the amount of energy going in via the foods and drinks we consume, the body can enter starvation mode, and the menstrual cycle can change. So, if notice changes to your period and you work out frequently, take a close look at your workout schedule.

Hormonal imbalances

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.


Thyroid dysfunction

The thyroid, a small gland in your neck, plays a significant role in regulating the menstrual cycle, and changes in your period can be a clue that your thyroid isn't functioning properly. According to naturopathic doctor Lara Briden, heavier, longer periods are usually the result of an underactive thyroid, while lighter, shorter periods are typically caused by an overactive thyroid, also known as hyperthyroidism (via Society for Menstrual Cycle Research).


Hyperthyroidism impacts your menstrual cycle in a few key ways. First, it changes the way the pituitary gland produces and releases LSH and FSH, two hormones that trigger the menstrual cycle. An overactive thyroid also increases the amount of sex hormone-binding globulin in your body, which reduces your estrogen levels, making periods shorter and lighter. Finally, hyperthyroidism changes the way your blood clots, which causes you to bleed less during your period.

Thyroid dysfunction often isn't high on the list of possible causes for shorter, lighter periods. However, if other possible causes have been ruled out, thyroid function tests might be warranted.

Polycystic Ovarian Syndrome (PCOS)

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.


Medications other than birth control

Hormonal birth control is the medication most likely to cause changes to your period, but there are other medications that can cause shorter, lighter periods. In a reference guide for VisualDx, Drs. Mitchell Linder and Paritosh Prasad state that some medications prescribed for non-menstrual medical conditions can cause irregular periods.


Some medications prescribed for epilepsy can increase the levels of sex hormone-binding globulin (SHBG) in the body, which leads to a decrease in estrogen. This decrease can make periods lighter and shorter or stop periods completely. Other anti-epileptic medications can increase the amount of androgens, or male hormones, the body produces. This creates hormone imbalances that disrupt the menstrual cycle and can even lead to PCOS.

Certain antipsychotic medications can also can irregular periods. This happens because they disrupt the body's levels of prolactin, a hormone that rises during pregnancy and breastfeeding. When the levels of this hormone are too high when someone isn't pregnant, it can cause short, light periods, or stop periods. And anabolic steroids, which may be prescribed for certain medical conditions or abused by athletes, can be another cause of light, short periods.


If you notice that your period is suddenly shorter after you start medications that fall into any of these categories, let your doctor know. This can be a sign that the medication is causing a hormonal imbalance, and your doctor will need to decide if the benefits outweigh the side effects of your shorter menstrual cycle.

Primary Ovarian Insufficiency (POI)

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.


Uterine scarring

A rare reason for shorter, lighter periods is uterine scarring. Also called Asherman's syndrome, uterine scarring occurs when scar tissue builds up inside the uterus. This condition typically only occurs if you've had a previous surgery involving your uterus or if you've had a pelvic infection that spread to the uterus.


During a period, the lining of the uterus, called the endometrium, sheds from the lining of the uterus, and exits the body through the cervix, then the vagina. What we call period blood is actually the endometrium, the lining of the uterus. When scar tissue builds up in the endometrium it can't shed the way it's supposed to during menstruation. Sometimes, less of the endometrium sheds, leading to shorter, lighter periods. Sometimes, the scar tissue prevents the endometrium from shedding at all, leading to skipped periods.

Unless you've had surgery or recurrent pelvic infections, uterine scarring probably isn't the cause of your shorter periods. But if you have had surgery that involved your uterus, such as a cesarean section birth or an endometrial ablation, or recurrent pelvic infections, talk to your doctor about whether uterine scarring is a possibility.



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.

Should I worry about a shorter period?

Everyone's menstrual cycle is different, and only you know what's normal for you. If your periods are always a bit irregular, shorter periods may not be a big deal. And even if your period has always been regular, one shorter period probably isn't anything to worry about.


That being said, any sudden changes to your period are worth a note to your doctor, says Ellyn Vohnoutka, a nurse with over 13 years of experience (via Ro). You probably won't need an appointment for one shorter period, but it's still something your doctor should know about.

After one shorter or lighter period, track your periods for a few months to see if you notice any patterns. If you have one shorter period then all the periods after it are normal, it was probably a fluke. But if you notice a few shorter periods in a row or your periods fluctuate between short and long, make an appointment with your primary care doctor or gynecologist.

During the time you're tracking your periods, it's also helpful to track your sleep patterns, stress levels, weight, and exercise routine. This gives your doctor the information they need to determine whether your lifestyle is contributing to your irregular periods. The bottom line is that shorter periods are likely related to your lifestyle, medications, or age and not a serious underlying condition. Just keep your doctor in the loop.