The menstrual cycle in women cannot be always precisely according to the scheduled clockwork. It may vary from one month to the next. While some women may get their periods in exact 28 days’ cycle while others may experience an unpredictable menstrual cycle.
A normal menstrual cycle lasts 28 days. An approximate plus or minus of seven days can be seen in this cyclic occurrence. Menstruation can be said to be irregular if it occurs more frequently than every 21 days or lasts longer than 8 days. Delayed, missed or early periods can also be said to be irregular. To determine whether your menstrual cycle is irregular, count from the last day of your previous period and stop counting on the first day of your next. Repeat this for three months. If the number of days between stopping and starting your period is significantly different each month, you have an irregular cycle.

Following may be certain reasons of having irregular periods-
- Anovulation– Many a time the egg is not released from the ovary. This may happen due to hormonal imbalance.
- Extreme workout/dieting– Undergoing extremely strenuous workout may alter the cyclic occurrence of menstruation. It is a common thing for endurance athletes to miss out their periods. Being underweight due to extreme exercise, dieting or eating disorder may also result in this.
- Stress– Having chronic stress or a short-term anxiety may alter the hormonal balance leading to irregular periods.
- Pills– Birth control pills can either make your periods lighter, irregular or may also lead to missing it out.
- Age– In most of the teens, during the initial days of their menstruation cycle, it may not be regular. It may take a certain time for getting set to an almost fixed pattern. Also during the time of menopause, some women may experience light, heavy or missing of periods.
If you are constantly facing an irregularity in your periods then you ought to consult an expert.

PCOS– Polycystic ovary syndrome. This accounts for interference in ovulation (due to the cysts being formed on ovaries).
Having thyroid conditions may also alter the period regularities.
In case you are going through irregular periods due to heavy exercises then avoid doing so.
To avoid period irregularities due to stress, go for meditation, yoga etc.