During doctor appointments, women are often asked when they last had their period. You might keep track of your menstrual cycle, but do you understand the changes your body goes through each month? 


In this blog, we’ll explore how the menstrual cycle works, what to note when you track your period, and the symptoms and possible causes of irregular periods. Keep reading to learn more!

What is the Menstrual Cycle?

The menstrual cycle is the changes your body goes through each month to prepare for pregnancy[1]. During this time, one of the ovaries releases an egg (which is called ovulation). If the egg isn’t fertilized following ovulation, the lining of the uterus sheds through the vagina, causing vaginal bleeding. This is what’s known as your menstrual period[1].


There are four different phases in the menstrual cycle, which are triggered by the fluctuations of your hormones[2]:


The menses phase. This phase starts on the first day of your period. It’s when the uterine lining sheds through the vagina if the released egg was never fertilized.


The follicular phase. This phase also starts when you get your period and ends at ovulation. During this time, your estrogen level rises, causing the lining of your uterus to thicken and grow. Another hormone, called follicle-stimulating hormone (FSH), causes follicles in your ovaries to grow and produce an ovum (mature egg). 


Ovulation. Ovulation occurs when another hormone, called luteinizing hormone (LH) begins to increase and causes your ovary to release the egg. Ovulation typically occurs about halfway through a menstrual cycle. For an average 28-day cycle, this is around day 14, but the actual timing can vary from person to person. 


The luteal phase. During the luteal phase, the egg leaves your ovary and travels through your fallopian tube to your uterus. The hormone progesterone increases to help your uterus prepare for pregnancy. If the egg is fertilized during intercourse, you have become pregnant, and the egg will eventually implant into the uterus. If the egg does not implant, your progesterone and estrogen levels will decrease and the thickened lining of your uterus sheds itself during your period. This phase lasts from about day 15 to day 28 of the menstrual cycle. 

How Long is the Menstrual Cycle? How Long Should Your Period Last?

Menstrual cycles typically span between 21 to 35 days, with the average being 28 days[2]. A normal period (when you’re bleeding) lasts between 3 to 7 days[2].

What is an Irregular Period? What Causes Irregular Periods?

An irregular period is when your period is late or early, doesn’t come at all, or when the length of your menstrual cycle increases or decreases. Examples include[3]:


  • Periods that happen less than 21 days or more than 35 days apart.
  • Skipping 3 periods in a row, even though you aren’t pregnant.
  • Bleeding that lasts longer than 7 days. 
  • Menstrual flow that’s much lighter or heavier than usual.
  • Bleeding through one or more tampons or sanitary pads per hour.
  • Bleeding or spotting between periods.
  • Severe pain, cramping, nausea, or vomiting during your period.


Possible causes of irregular periods include: 


  • Extreme weight loss or exercise. Extreme weight loss (due to eating disorders or other causes) and exercise can interrupt your menstrual cycle[1].


  • Uterine fibroids. Uterine fibroids are noncancerous growths in the uterus that can cause prolonged and heavy periods[1]


  • Polycystic ovary syndrome (PCOS). Polycystic ovary syndrome (PCOS) is a condition that causes the ovaries to produce an unusually high amount of male sex hormones, called androgens. These hormones prevent the ovaries from releasing eggs, causing irregular periods[4]


  • Pelvic inflammatory disease (PID). Pelvic inflammatory disease (PID) is an infection of the female reproductive organs that can cause pain or bleeding between periods[5].


  • Primary ovarian insufficiency. Primary ovarian insufficiency (previously known as premature ovarian failure) is the loss of normal ovary function before 40. Women who have this condition may experience irregular periods for years[1] and may have difficulty becoming pregnant. 


  • Pregnancy or breastfeeding. A missed period is an early sign of pregnancy. Additionally, breastfeeding can delay the return of your period after giving birth[1].


If you think you may be experiencing an irregular period, speak to your doctor to receive a diagnosis and treatment, if needed. 

How to Track the Menstrual Cycle

It’s very easy to track your menstrual cycle! Some women use the calendar on their phones, while others use tracking apps. To figure out what’s normal for you, start tracking the following each month[1]


  • Start and end date. How long does your period last? Does it start and end at the same time each month or does it vary?


  • Pain. When do you experience cramping, if at all? How bad is the pain?


  • Bleeding patterns. What is your flow like? How often do you need to change your pad or tampon? Do you pass blood clots? Do you bleed in between periods?


  • Mood. Do you notice any changes in your mood when you get your period?


Knowing all of this will help you to better understand your menstrual cycle and manage your symptoms! 

Learn More About the Menstrual Cycle at CHOICES

It’s important to ask questions about your menstrual cycle, so you can better understand your body and protect your health! CHOICES is here to answer your questions, without judgment.  You can meet with a licensed registered nurse (RN) who cares about you and your health to ask questions or discover other resources.


To schedule your appointment, send a text to (719) 694-3201 or give us a call at (719) 284-2300 in Woodland Park or (719) 465-0123 in Cripple Creek. All services are free and confidential.


  1. Mayo Foundation for Medical Education and Research. (2023, April 22). Menstrual Cycle: What’s Normal, What’s Not. Mayo Clinic. https://www.mayoclinic.org/healthy-lifestyle/womens-health/in-depth/menstrual-cycle/art-20047186  
  2. Menstrual Cycle. Cleveland Clinic. (2022, December 9). https://my.clevelandclinic.org/health/articles/10132-menstrual-cycle  
  3. Irregular Periods (Abnormal Menstruation): Causes & Treatment. Cleveland Clinic. (2023, January 18). https://my.clevelandclinic.org/health/diseases/14633-abnormal-menstruation-periods  
  4. PCOS (Polycystic Ovary Syndrome): Symptoms & Treatment. Cleveland Clinic. (2023, February 15). https://my.clevelandclinic.org/health/diseases/8316-polycystic-ovary-syndrome-pcos  
  5. Mayo Foundation for Medical Education and Research. (2022, April 30). Pelvic inflammatory disease (PID). Mayo Clinic. https://www.mayoclinic.org/diseases-conditions/pelvic-inflammatory-disease/symptoms-causes/syc-20352594