Menstrual Cycles 101: An introduction to understanding your menstrual cycle

Written by: Gabriela Faragitakis 

Program: Level III Honours Biology & Psychology, Neuroscience, and Behaviour 

What is the menstrual cycle? 

The menstrual cycle describes the series of physiological events and hormonal changes that occur in individuals with uteruses each month. This includes cisgender women, transgender men, and non-binary individuals. Many people recognize menstruation, which refers to the shedding of the uterine lining, when vaginal bleeding occurs, also known as a period. However, the menstrual cycle is composed of so much more than one’s period.  

Menstrual cycles tend to be consistent in frequency, usually occurring every 21 to 35 days. However, the length varies between individuals and may change on a month-to-month basis. You can calculate the length of your menstrual cycle by counting the days between the first day of your current period and the first day of your next period. It is important to recognize everyone’s experience with their menstrual cycle will be different. Some may feel positive or neutral about it, while others may be extremely uncomfortable and in pain, or experience increased gender dysphoria. 

Why might my cycle be irregular? 

When you first begin your period, it may be irregular as your body begins to adjust to new hormone fluctuations. Other reasons for irregular periods could include: 

• Excess stress 

• Significant weight changes 

• Exercise 

• Taking certain medications 

• Birth control (e.g. IUDs may lighten or stop your period) 

• Pregnancy 

• Health Conditions (e.g. endometriosis, pelvic inflammatory disease, PCOS, etc.) 

If you are worried about your menstrual cycle and have experienced significant changes, or have questions about your irregular or missed periods, make an appointment with a doctor. 

What are the phases of the menstrual cycle? 

The menstrual cycle is composed of four phases: the menstrual phase, the follicular phase, the ovulation phase, and the luteal phase. 

Menstrual phase 

The menstrual phase occurs when an egg from the previous menstrual cycle is not fertilized by sperm. Because pregnancy did not occur, the thickened lining of the uterus- which would have supported a pregnancy, sheds; this shedding is known as your “period.” Menstruation typically lasts anywhere between 3-7 days. During this time, estrogen and progesterone levels drop. 

Common symptoms during the menstrual phase include: 

• Cramping 

• Bloating 

• Tender breasts 

• Mood swings/irritability 

• Headaches 

• Tiredness 

• Low back pain 

Note on Dysmenorrhea: 

People who menstruate may experience a wide range of symptoms. Some individuals may notice little to no symptoms, while others may experience many. Painful menstruation which causes a person to miss school or work is called dysmenorrhea. If you are looking for more information on dysmenorrhea, check out our previous Wellness@Mac article here: https://wellness.mcmaster.ca/cramping-our-style-the-hidden-impact-of-period-pain-on-students/ 

Follicular phase 

The follicular phase overlaps with the menstrual phase and starts on day 1 of your period and ends with ovulation. Follicle-stimulating hormone (FSH) is released, and luteinizing hormone (LH) levels rise. FSH and LH work together on the ovaries to support follicular growth. The ovaries will produce ~ 10-20 follicles (immature eggs), and the healthiest follicle will mature.  As follicles develop, they release estrogen; this triggers the uterine lining to thicken, creating a nutrient rich environment for a potential future embryo. The follicular phase tends to last 11-17 days. 

Ovulation phase 

Ovulation occurs around day 14 of the menstrual cycle with a spike in LH. It lasts    approximately 24 hours. A follicle ruptures and a mature egg is released into the fallopian tube. There is a chance of getting pregnant during the ovulation phase, as fertilization is possible if sperm is present. 

Common symptoms during the ovulation phase include: 

• A slight rise in basal body temperature 

• A change in discharge- typically, thicker with the consistency of egg whites 

Luteal phase: 

The luteal phase occurs after ovulation and lasts for around 11-17 days. The ruptured follicle becomes the corpus luteum. The corpus luteum secretes progesterone and some estrogen. Progesterone works to thicken the uterine lining and begins preparing for a possible pregnancy. If pregnancy were to occur, the body produces human chorionic gonadotropin (HCG); HCG prevents the corpus luteum from breaking down and maintains the thickening uterine walls. If pregnancy does not occur, then levels of estrogen and progesterone will fall, triggering the start of menstruation. The cycle then repeats. 

Common symptoms during the luteal phase include: 

• Bloating 

• Breast tenderness 

• Mood changes 

• Weight gain 

• Changes in sexual desire/libido 

• Food cravings 

• Trouble sleeping 

Navigating your menstrual cycle as a student: 

Navigating your menstrual cycle can be challenging no matter your stage of life, but it can be especially difficult as a student. With demanding deadlines and hectic schedules, it is easy to feel overwhelmed. Now add on top of that debilitating cramps and a persistent concern of where to access menstrual products. 

There is no single right way to approach your menstrual cycle, but here are some strategies that can help you manage yours: 

• Use a heating pad (i.e. electric blanket, heated water bottle) to help alleviate cramping, as well as general body aches. 

• Exercise! Going for a walk or participating in a yoga class can trigger your body to release hormones that make you feel good. 

• Take a bath to help relieve muscle tension and relax.  

• Stay hydrated! Drinking water or tea can help reduce bloating and prevent headaches. 

• Carry Advil or Tylenol on you in case you ever want pain management options. 

• Talk to a doctor if you are experiencing painful periods. Despite cramping being common, it is not normal for you to be in excruciating pain throughout your period. 

• Use an app to help track the beginning of your menstrual cycle. Predictions are not always completely accurate, but they can help you feel informed and in control of your cycle.  Knowing the approximate start and end days of your period can also help in terms of scheduling. 

• Reflect on the symptoms you experience throughout your menstrual cycle. Many people experience more intense cramping and discomfort at the beginning of their period. If so, consider prioritizing assignments and other work before or after the start of your period. 

• Pack extra menstrual products (pads, tampons, etc.) or access free ones on campus (i.e. from SWC, WGEN, SHEC). 

• Try to be kind to yourself. Journaling and writing positive affirmations can be positive reminders that brighten up your day.  

Places to access support on campus: 

• Women and Gender Equity Network (WGEN) and the Student Health Education Centre (SHEC) offer free menstrual products, along with peer support.  

• WGEN is located in MUSC 204. 

• SHEC is located in MUSC 202. 

• The Student Wellness Centre (SWC), located in PGCLL Level 2, offers free menstrual products, along with health outreach programs, counseling services, and medical care.  

• You can book a medical appointment with the SWC in person or by calling reception at 905-525-9140 ext. 27700.  

• The SWC runs #SexTalkTuesday, a weekly Instagram series that aims to address sexual health questions students have. If you ever have a question you would like answered, you can anonymously submit it through the link in the “mcmasterswc” Instagram bio. 

It can be intimidating to reach out for support from a healthcare provider, especially if your symptoms have been dismissed in the past. Bringing a trusted friend or family member to your appointment or jotting down a list of your questions ahead of time to help make things feel less overwhelming. 

Resources: 

Student Wellness Centre (SWC): https://wellness.mcmaster.ca/ 

Women & Gender Equity Network (WGEN): https://msumcmaster.ca/service/wgen/ 

Student Health Education Network (SHEC): https://msumcmaster.ca/service/shec/ 

References 

Betz, D., & Fane, K. (2023). Human Chorionic Gonadotropin (HCG). National Library of 

Medicine; StatPearls Publishing. https://www.ncbi.nlm.nih.gov/books/NBK532950/ 

Birth control lets you decide when to have your period. (2025). Mayo Clinic.  

https://www.mayoclinic.org/tests-procedures/combination-birth-control-pills/in-depth/womens-health/art-20044044 

Cleveland Clinic. (2022). Menstrual cycle. Cleveland Clinic. 

https://my.clevelandclinic.org/health/articles/10132-menstrual-cycle 

Hawkins, S. M., & Matzuk, M. M. (2008). The Menstrual Cycle. Annals of the New York 

Academy of Sciences, 1135(1), 10–18. https://doi.org/10.1196/annals.1429.018 

Itriyeva, K. (2022). The normal menstrual cycle. Current Problems in Pediatric and Adolescent Health Care, 52(5), 101183. 

https://doi.org/10.1016/j.cppeds.2022.101183 

Leung, P. C. K. (2019). The Ovary (Third Edition). Academic Press. 

Schoep, M. E., Nieboer, T. E., van der Zanden, M., Braat, D. D. M., & Nap, A. W. (2019). The impact of menstrual symptoms on everyday life: a survey among 42,879 women. American Journal of Obstetrics and Gynecology, 220(6), 569.e1–569.e7. https://doi.org/10.1016/j.ajog.2019.02.048 

Thiyagarajan, D. K., Basit, H., & Jeanmonod, R. (2024). Physiology, menstrual cycle. National Library of Medicine; StatPearls Publishing. 

https://www.ncbi.nlm.nih.gov/books/NBK500020/