Top Reasons For An Irregularly Long Cycle

A normal cycle is considered to be 21-35 days, with the first day being the first day of your period and the last day being the day before you start your period. Anything over 35 days is considered an irregular cycle, and a cycle missed for three months in a row is considered “secondary amenorrhea.” The female body is a complex system of hormones, and if one hormone is off, this can cause all of the other hormones to go haywire as well.

It may at first sound great to have a longer than normal cycle – less periods, yay! Unfortunately, the deeper issue here is that this is a clear sign from your body that your hormones are off. This could be a one-time thing, or it could be something that happens regularly, and understanding the various causes is important for your hormonal health down the road.

Below lists the most common causes of an irregularly long cycle:

1. PCOS (Polycystic ovarian syndrome)

This is complex disorder that is not fully understood but is considered a hormonal disorder where the body is producing higher than normal amounts of insulin and male hormones, which then causes the main hormones involved with ovulation to decrease, and thus prevents an egg from being released. [1].


A low-carb diet is recommended to lower insulin and to regulate hormones involved with ovulation. Hormones may also be recommended to help control elevated male hormones.

2. Endometriosis

This is another complex disorder where the tissue that normally lines the inside of the uterus, grows outside of the uterus.The hallmark of this disorder is extremely painful and heavy periods, which may be irregular in length [2].


Treatment varies but can include the use of hormones and/or surgery.

3. Stress

High levels of stress can lead to an irregular cycle due to the increased presence of stress hormone itself, most notably cortisol. High cortisol can act to block the release of gonadotropin-releasing hormone (GnRH) which is needed to stimulate follicle stimulating hormone (FSH) and luteinizing hormone (LH). FSH and LH are hormones needed to get a follicle ready for ovulation and also to trigger ovulation. In condensed words, this means that the presence of elevated stress hormone prevents ovulation from happening. [5].


Decrease stress in your life by practicing yoga, meditation, and exercising most days of the week.

4. Underactive thyroid

Hypothyroidism, meaning too low of active thyroid hormones, can disrupt your monthly cycle of hormones for a couple of reasons. One reason this happens is that abnormal levels of thyroid hormones may increase the prolactin level, and prolactin can inhibit release of certain hormones that are needed to cause ovulation (more on this below). [4]. Another possible reason is that abnormal levels of thyroid hormones with hypothyroidism is also associated with a high cortisol level (high stress level). As discussed above, this elevation in stress hormone can inhibit ovulation. [6].


Hypothyroidism is typically treated with giving thyroid hormone medication.

5. Not enough body fat

A body fat percentage of under 18% can lead to loss of a period, but this body fat percentage varies greatly from woman to woman. I have had patients with 10% body fat who still had a normal cycle, but again, anything lower than 18% can disrupt your hormones.

There are a couple of reasons why too low of body fat may lead to an irregular cycle. One is that body fat is needed to produce enough estrogen, which is a prime hormone of ovulation. Another is that too low of body fat beyond what the body wants, can be stressful on the body, leading to higher stress hormone and thus shutting off the hormone cascade needed for ovulation. Another potential reason is decreased leptin, which is a hormone that plays a role in stimulating the cascade of hormones needed for ovulation. [8]


Eat more, specifically eat more healthy fats (read here for a list of the best sources), and cut back on exercise if you are exercising excessively – no more than 30 minutes of high intensity exercise a few times a week.

6. Note enough calories

Restricting calories too much can lead to higher stress levels in the body, which as you learned above, can disrupt the flow of hormones involved with your cycle. If your calorie intake is too low, your body may not have the building blocks it needs to produce hormones involved with your cycle. If too low of calories leads to too low of body fat, then this can also disrupt normal ovulation[.7] Again leptin may come into play here, because underfeeding is associated with low leptin levels, and we learned above that leptin is involved in the cascade of events that happen with ovulation.


Eat more. Again, this means eat more healthy food. Add coconut oil to your eggs, double to the amount of almond butter you are putting in your smoothie, etc.

7. Too much exercise

Exercise is amazing for your body and I recommend exercise as a treatment for many different conditions. That being said, too much of anything is not goof for you, and the same applies to exercise. Too much exercise can throw off your period for a few different reasons. One is that it too much exercise can lead to build-up of cortisol (stress) in the body, which we learned can shut off ovulation. Another reason is that if too much exercise is causing too low of body fat, this can also turn off ovulation. 

It’s hard to define exactly what is too much exercise, but if you are spending an hour or more daily doing high intensity exercise, that’s probably too much. Tune in with your body, if you are starting to get pain or an injury is developing, this is your body telling you to scale it back.


Limit high intensity exercise to 30 minutes, increase low impact and stress-reducing exercises such as yoga and walking.

8. Pituitary gland tumor

This is usually discovered once all other causes have been ruled out. It involves getting an MRI of your brain which can be scary and also costly. The most common pituitary gland tumor is prolactinoma, a tumor that causes an increase in production of the hormone prolactin. Prolactin inhibits the secretion of the gonadotropin-releasing hormone, GnRH. GnRH under normal circumstances, functions to stimulate the release of FSH and LH which are hormones that are directly involved with maturing a follicle in the ovary to release an egg (aka ovulation). An elevated prolactin level may prompt an MRI if no other cause can be determined. 3


Typical treatment for this is medication to shrink the tumor or surgery to remove it.

Important note:

Prolactin is elevated during breastfeeding, which is why most women will not ovulate while breastfeeding. For this reason, breastfeeding is thought to act as a form of natural birth control.

Main take aways…

Your monthly cycle is all about hormones, if you are not having a regular cycle, this is a clear indication that one or more of your hormones is not functioning as it should. If your cycle continues to be irregular, it is a good idea to see your healthcare provider for an exam and to have your hormone levels checked as well.



About the author: Sarah-Kate Rems is an Ivy-league trained Board-Certified Family Nurse Practitioner licensed in California with an expertise in women’s health and preventative healthcare. She considers nutrition and exercise to be the basis of well-being and is a strong advocate for daily physical activity and maintaining a healthy diet. Sarah-Kate is also a co-founder of The Mindful Tech Lab

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