Why Is My Period Late? Common Causes of Delayed Menstruation

How Late Is Considered a Delayed Period?

Typically, your menstrual cycle lasts anywhere from 21 to 35 days. An average cycle is approximately 28 days long.

Your period would typically be considered "late" once your menstruation has not appeared five or more days past your expected due date.

Secondary amenorrhea (missing your period for three consecutive months) is defined as a medical concern requiring evaluation.

What Causes a Delayed or Missed Period?

There are several reasons why your menstrual cycle could be disrupted: 

• Pregnancy 
• Significant amounts of stress
• Hormone imbalances (such as PCOS/PMOS or thyroid disorder)
• Sudden significant weight fluctuations 
• Excessive exercise
• Certain prescription medications (e.g., hormonal birth control) 
• Perimenopause 
• Chronic illness or infection 

By tracking your cycle length and any symptoms that develop, you can work with your physician to determine the cause of the disruption.

Can Stress Cause a Late Period?

Stress can be a factor in delaying your menstrual cycle. 

High stress levels affect the hormone that regulates ovulation. When ovulation does not occur on schedule, the resulting cycle will either be pushed back or will not occur at all. 

Moreover, stress experienced during the menstrual cycle (perceived stress) significantly impacts menstrual cycle duration, blood flow, and pain associated with menstruation. 

Can PCOS/PMOS Cause Delayed or Irregular Periods?

Polycystic ovary syndrome (PCOS/PMOS) is among the most common endocrine disorders, affecting the frequency of menstrual cycles. 

Women who suffer from PCOS/PMOS experience an abnormal balance of reproductive hormones that prevents them from consistently ovulating. 

Women suffering from PCOS/PMOS experience oligomenorrhea, which is infrequent menstruation with cycles occurring less frequently than every 35 days. 

This pattern is also closely tied to insulin resistance. Additional signs of PCOS/PMOS include acne, hirsutism, and weight fluctuations.

Can a Late Period Be a Sign of Pregnancy?

A late period is likely one of the earliest signs of pregnancy. If you are sexually active and your menstruation has been delayed, take a home pregnancy test. 

To ensure accuracy, wait a few days after your missed period before taking the test. Even then, if your test indicates that you are not pregnant, contact your physician to discuss further options.

Other Reasons Your Period May Be Late

In addition to stress, PCOS/PMOS, and pregnancy, other contributing factors include the following: 

• Thyroid disorders: Both hypothyroidism and hyperthyroidism can cause disruptions in your menstrual cycle.
• Weight fluctuations: Large increases or decreases in weight within a short timeframe can affect the hormones responsible for regulating ovulation.
• Excessive exercise: While regular moderate-intensity exercise generally promotes good health, extreme exercise regimens combined with low body fat levels can inhibit the production of hormones necessary for maintaining regular ovulation. 
• Medication changes: Initiation, discontinuation, or change of hormonal birth control can temporarily alter menstrual patterns. 
• Perimenopause: As you transition into menopause, hormonal fluctuations can make menstrual cycles irregular.
• Chronic illnesses: Certain chronic illnesses, such as diabetes or celiac disease, can impact menstrual regularity.

What Should You Do If Your Period Is Late?

If your next menstruation is just a few days overdue, there is little reason for alarm. Your next steps can include the following:

1. Take a home pregnancy test if you suspect pregnancy. 
2. Track your cycle for the next couple of months.
3. Note whether you have recently had any changes in stress levels, health status, or lifestyle. 
4. Avoid making radical diet/exercise adjustments until you understand the cause. 
5. Contact a physician if the delay persists or if additional symptoms appear.

When Should You See a Doctor About a Late Period?

Schedule a visit with your physician when: 

• You have missed three or more consecutive periods after having regular cycles; they suddenly became erratic. 
• You are experiencing severe pelvic discomfort before menstruation. 
• You are experiencing unusual symptoms, such as rapid hair growth. 
• You are unexpectedly gaining or losing weight. 
• You believe you may be pregnant. 
• You are attempting to conceive.
• Your cycles are inconsistent.

How Is the Cause of a Delayed Period Diagnosed?

Late menstrual cycles typically begin with the physician collecting information regarding your cycle, lifestyle, and current medical status. The physician may ask for the following tests:

• A pregnancy test
• Blood tests to evaluate your hormone levels, including those associated with thyroid function
• Pelvic ultrasound to identify potential ovarian cysts and/or anatomical abnormalities. 

Bring a copy of your most recent cycle lengths with you to the appointment; this could possibly expedite identification.

Can Delayed Periods Be Treated?

The manner in which you are treated will depend upon the reason(s) why your menstrual cycles were delayed. 

After identifying the reason for your delayed menstrual cycles, the physician will be able to develop a plan to treat you based upon your specific situation. The approaches may include the following: 

• Some type of lifestyle modification (e.g., managing stress)
• Hormonal birth control to manage your menstrual cycle
• Medication to address polycystic ovarian syndrome (PCOS/PMOS) or hyper/hypothyroidism
• Dietary support related to possible weight gain or loss issues
• Continued evaluation if there is no apparent cause for the delay. 

Most causes of delayed menstrual cycles can be effectively managed once identified.

References 

• Gordon, C. M., Ackerman, K. E., Berga, S. L., Kaplan, L. M., Mastorakos, G., Misra, M., Murad, M. H., Santoro, N. F., & Warren, M. P. (2017). Functional hypothalamic amenorrhea: An Endocrine Society clinical practice guideline. The Journal of Clinical Endocrinology & Metabolism, 102(5), 1413-1439. 
• Hussein, K., & Karami, M. (2023). Association between insulin resistance and abnormal menstrual cycle in Saudi females with polycystic ovary syndrome. Saudi Pharmaceutical Journal, 31(6), 1104-1108. 
• Master-Hunter, T., & Heiman, D. L. (2006). Amenorrhea: Evaluation and treatment. American Family Physician, 73(8), 1374-1382.
• Nagma, S., Kapoor, G., Bharti, R., Batra, A., Batra, A., Aggarwal, A., & Sablok, A. (2015). To evaluate the effect of perceived stress on menstrual function. Journal of Clinical and Diagnostic Research, 9(3), QC01-QC03. 
• Fritz, M. A., & Speroff, L. (2011). Clinical gynecologic endocrinology and infertility: Anovulation and ovulatory disorders. Fertility and Sterility, 95(4), 1137–1145.