Quick version
Irregular periods mean that the cycle varies by more than 7 days, comes too infrequently or frequently, is absent for longer periods or has unusually heavy or scanty bleeding.
Common causes of irregular periods are hormonal changes, stress, PCOS, thyroid disorders, weight loss, overtraining, pregnancy and breastfeeding. Periods can become irregular around the age of 40, during menopause or after childbirth.
Ovulation usually occurs 14 days before menstruation, but is more difficult to predict with irregular cycles. Seek medical attention if menstruation is absent for more than three months, if bleeding is very heavy or if other symptoms such as fatigue or hair loss occur.
What is irregular menstruation?
The menstrual cycle varies from person to person, but a normal cycle is usually between 21 and 35 days. A period is considered irregular if:
- The cycle varies by more than 7 days from month to month.
- The period is absent for extended periods without pregnancy.
- The bleeding is very heavy or unusually light.
- The period comes more often than every 21 days or less often than every 35 days.
Causes of irregular menstruation
Irregular menstruation can be due to several different reasons, with hormonal changes being a common reason. Here are some common causes of irregular periods:
- Puberty – When you enter puberty, it can take time for your body to find a stable cycle.
- Stress – Hormone balance can be affected by high levels of stress, which in turn can disrupt your menstrual cycle.
- Menopause – Menopause often becomes irregular during the transition to menopause.
- PCOS (polycystic ovary syndrome) – The condition involves a hormonal disorder that can lead to irregular or absent periods.
- Severe weight loss or overtraining – In the event of major physical stress such as severe weight loss or extreme overtraining, ovulation can be affected, thus making your period irregular.
- Pregnancy and breastfeeding – Before your period has had time to become regular after a childbirth, it may take time for it to stabilize and become regular again.
- Thyroid disorders – Conditions such as hypothyroidism (underproduction of thyroid hormone) or hyperthyroidism (overproduction of thyroid hormone) can affect the menstrual cycle.
Sudden irregular periods
Stress, hormonal changes, weight changes, or other underlying conditions can cause a sudden irregular period. Seek medical attention if your period is missed for more than three months without pregnancy for help with further assessment.
Irregular periods around age 40
Many women notice changes in their periods around age 40. This is often related to the body preparing for menopause. Menstruation can then become shorter, longer, heavier, less frequent or more irregular.
Irregular periods during menopause
Perimenopause, which is the period before menopause, can last for several years and is often characterized by irregular periods. During this period, bleeding can become more unpredictable before finally stopping completely when menopause occurs.
Menstruation after pregnancy – when does it become regular again?
After a pregnancy, it is common for menstruation to be irregular and it may take a while before it becomes regular again. If you are not breastfeeding, menstruation can return within 6–8 weeks. When breastfeeding, menstruation can be irregular or absent for several months. It varies from person to person.
When do you ovulate with irregular periods?
Ovulation can be more difficult to predict with irregular periods. Ovulation generally occurs about 14 days before your next period. There are tests and apps that can help identify ovulation by measuring hormone levels or body temperature.
How late can your period be?
It's not uncommon for your period to be a few days late, but if you find that it's more than a week late and you're not pregnant, it could be a sign of a hormonal imbalance. In case of repeated delays, it may be a good idea to investigate possible underlying causes.
When should you seek medical attention?
If you experience the following symptoms and changes, it may be a good idea to seek medical attention for your symptoms and further help with investigation or treatment:
- Missed period for more than three months without pregnancy.
- Irregular period with very heavy or painful bleeding.
- Sudden change in bleeding pattern without a known cause.
- Other symptoms such as fatigue, weight changes or hair loss, which may indicate hormonal problems.
Irregular periods are common and can be due to several factors. If you are unsure or are bothered by your period, it is always a good idea to contact a doctor for an investigation.
