A woman’s monthly flow or period is one the most discussed feature of a woman. Concerns about what makes a menstrual flow normal or abnormal, regular or irregular, heavy or scanty, are subjects which many women worldwide, can relate to on a daily basis. It is not unusual for women to show concern or worry whenever their menstrual flow is delayed. While many women can characterize their monthly period, many others are unable to wrap their head around it. Thus, we will be using this opportunity to discuss what makes a menstrual cycle, normal or abnormal and how to identify if your menstrual cycle is regular or irregular.



A woman is said to have a normal menstrual cycle, if each cycle is associated with the regular process of ovulation and void of interference by pelvic diseases.

Such cycles referred to as ovulatory cycles are characterized by the following features:

1) The cycle length must be between 21 days to 35 days long; the cycle length is the number of days from the beginning of one menstrual cycle to the beginning of the next. The first day of your menstrual cycle is also the same as the first day of your menstruation. So to calculate your cycle length, count the number of days from the beginning of your current menses to the beginning of your next menses, taking care not to add the first day of the next menses to the count. If your cycle length falls between 21 days to 35 days then your menstrual cycle is normal but if it is shorter than 21 days or longer than 35 days, then it is abnormal.

2) Every woman should have a regular menstrual flow pattern that lasts about 2 to 8 days; any menstrual flow that is shorter than 2 days or longer than 8 days is abnormal. Despite this, if you observe a change in the pattern of your menstrual flow, for example, from a five day normal menstrual flow to a two day reduced menstrual flow or to a five day heavy menstrual flow associated with heavy clots, then, that menstrual flow is abnormal.

3) The length of the menstrual cycles, when observed for a period of six months, must not vary by more than 5 days; By keeping your menstrual dates for a period of atleast six months, calculate the cycle lengths of each period as described above and subtract your shortest cycle length from your longest cycle length. If the difference is less than or equal to 5 days, then your menstrual cycle is regular and associated with regular monthly ovulation, but if it is more than 5 days, then your menstrual cycles are irregular, suggesting that you ovulate irregularly or occasionally.

4) The follicular phase of the menstrual cycle, varies very little in the same woman but varies considerably more in different women; there is a subtle difference of about few days (5 days or less) in the menstrual cycle length of the same person over a certain period of time, due to a normal and slight variation in the length of the follicular phase of every woman. The follicular phase is the period spanning from the beginning of the menstrual cycle/flow to the day of the ovulation. However, a much larger variation in the length of the follicular phase occur among all women, accounting for the marked difference in their cycle lengths, ranging from 21 days to 35 days in all women with regular menstrual cycles. 

5) In all women, the luteal phase is relatively constant, lasting about 14 days; the luteal phase is the period starting from the day of ovulation till the beginning of the next menses. It is relatively constant, lasting about 14 days in all women ovulating regulalrly. So if the normal cycle length is about 21 to 35 days and the luteal phase is approximately 14 days, then the follicular phase varies from 7 days to 21 days in all women.

6) Ovulation usually occurs about 14 days before the next menstrual date; Because the luteal phase is about 14 days long, women with regular menstrual cycles, can anticipate their next mentrual date and in so doing can anticipate their ovulation period which is simply 14 days before the next anticipated menses and not 14 days from the beginning of every menses, as often done errorneously by some women, unless in women with a 28 day menstrual cycle. In other words, if your cycle legth is 32 days long, then the ovuation period is on day 32 – 14 = day 18 of her cycle or 14 days from your next menses.



These are cycles which have features at variance with that described above for normal menstrual cycles. These include irregular menstrual cycles, regular but scanty or heavy menstrual cycles, regular but prolonged menstral cycles and cycles with abnormal bleeding in between menstrual periods.

Features of such cycles include:

1) Cycle length less than 21 days or longer than 35 days; irregular cycles are notoriously associated with menstrual cycles longer than 5 weeks (35 days) or shorter than 3 weeks (21 days). In some instances, these menses skip many months before the next menses is seen. These cycles are typically void or absent of ovulation and as such referred to as anovulatory cycles

2) Menstrual flow shorter than 2 days or longer than 8 days and or a significant change in the volume and duration of  a menstrual flow different from the normal flow.

3) Variation in the cycle length greater than 5 days in a six month period; because these cycles are irregular in nature and anovulatory in nature, they do not have any particuar pattern, hence it is common to have menstrual  cycles whose cycle lengths differ by more than 5 days and in some cases by many weeks or months.

Common causes of irregular cycles are disorders of ovulation such as polycystic ovarian syndrome (PCOS), hyperprolactinaemia, immaturity of the HPO axis, premature ovarian failure and perimenopause. Common causes of heavy but regular menstrual flow include uterine fibroids, endometrial hyperplasia, endometrial polyps and adenomyosis while common causes of scanty or reduced menstrual flow include uterine synechiae, cervical stenosis and gynaetresia. For a sneak peak into common disorders of menstruation, please read the article COMMON MENSTRUAL DISORDERS: AN OVERVIEW AND DEFINITION OF TERMS. Because abnormal menstrual cycles are basically features of various other diseases that may be associated with infertility, miscarriages, aneamia among many other complications of the primary disease, it is important that any woman with abnormal menstrual cycles should seek urgent medical attention in order to unearth the underlying cause of the problem. For an online consultation please CHAT WITH OUR CONSULTANTS.