Irregular menstrual periods

Irregular menstrual periods do not follow your usual pattern. They may come earlier or later than expected, stop for a time, or differ in length or flow. You may also have spotting between periods.

A menstrual cycle is counted from the first day of one period to the first day of the next. Some month-to-month change is common. What matters is whether the pattern is new, persistent, difficult to manage, or linked with other symptoms.

Irregular periods are a symptom, not one diagnosis. They often reflect changes in hormones, which are chemical messengers that control ovulation and menstruation. Pregnancy, medicines, health conditions, and major changes in daily life can also affect cycles.

Your periods may:

• Come unpredictably, with cycles that change noticeably in length
• Happen more or less often than usual
• Stop for several months
• Last longer or shorter than your usual period
• Be much lighter or heavier than usual
• Include bleeding or spotting between periods

Other symptoms can offer clues. These may include pelvic pain, acne, increased facial or body hair, hot flushes, vaginal dryness, weight changes, tiredness, or milky discharge from the nipples.

Keep in mind that bleeding after sex or after menopause is not simply an irregular period. It should be discussed with a healthcare professional.

Irregular cycles are common when the body’s hormone patterns are changing. This can happen during the first few years after periods begin and during perimenopause, the years leading up to menopause.

Other common causes include:

• Hormonal contraception: Pills, injections, implants, and hormonal intrauterine devices can change bleeding patterns or stop periods
• Stress or disrupted routines: Emotional strain, travel, shift work, or poor sleep may affect ovulation
• Weight, eating, or exercise changes: Significant weight loss or gain, low energy intake, or intensive exercise can interrupt cycles
• Pregnancy and breastfeeding: Pregnancy stops periods, while cycles may be irregular after birth and during breastfeeding

Less common causes include polycystic ovary syndrome, known as PCOS; thyroid problems; high levels of the hormone prolactin; uterine fibroids or polyps; some long-term illnesses; and certain medicines.

Rarely, irregular bleeding is related to a pregnancy complication, a bleeding disorder, or changes in the lining of the uterus or cervix. Symptoms and testing are needed to tell these possibilities apart.

Seek emergency care if bleeding is very heavy and you feel faint, weak, short of breath, or have chest pain. One warning pattern is soaking through a pad or tampon every hour for more than two hours, especially when these other symptoms are present.

Get same-day medical advice if you could be pregnant and have bleeding with severe or one-sided pelvic pain, shoulder-tip pain, marked dizziness, or fainting. These can be signs of an ectopic pregnancy, when a pregnancy develops outside the uterus.

You should also seek prompt care for sudden severe pelvic pain, heavy bleeding that is difficult to contain, or bleeding with fever and feeling seriously unwell.

Book a routine appointment if:

• Your periods stop for three months and pregnancy is not the reason
• A new irregular pattern continues
• Bleeding repeatedly happens between periods or after sex
• Period pain or bleeding interferes with school, work, sleep, or daily activities
• You have symptoms such as unusual hair growth, nipple discharge, hot flushes, or unexplained weight change
• You bleed after menopause, meaning after 12 months without a period

A healthcare professional will ask about your usual cycle, when the changes began, the amount of bleeding, pain, medicines, contraception, sexual health, pregnancy possibility, stress, eating patterns, and exercise.

A pregnancy test is often an early step when pregnancy is possible. Blood tests may check for anaemia, which means too few healthy red blood cells, as well as thyroid or other hormone problems.

Depending on your symptoms, you may be offered an examination, testing for sexually transmitted infections, or an ultrasound. An ultrasound uses sound waves to look at the uterus and ovaries.

Some people need further tests, such as a sample from the uterine lining. This is not required for everyone; the decision depends on factors such as age, bleeding pattern, medical history, and ultrasound findings.

Treatment depends on the cause, the amount of bleeding, your overall health, and whether you want contraception or hope to become pregnant.

A clinician may suggest monitoring the pattern, changing contraception, or using hormonal treatment to make bleeding more predictable or reduce it. Other medicines can reduce heavy bleeding. If a thyroid problem, PCOS, infection, fibroid, or another condition is found, treatment can be directed toward that cause.

Do not start iron supplements solely because bleeding is irregular. A blood test can show whether you have iron deficiency or anaemia, and a healthcare professional can advise whether treatment is needed.

You can support your assessment by tracking:

• The first and last day of each period
• Spotting between periods
• How often you change menstrual products
• Clots, leaks, pain, dizziness, and other symptoms
• Contraception, medicines, and pregnancy-test results

Regular meals, enough energy for your activity level, rest, and manageable exercise may help when stress or under-fuelling contributes. These measures do not replace assessment when bleeding is persistent or concerning.

Irregular periods caused by puberty, contraception, breastfeeding, stress, or perimenopause may settle or change over time. Other causes may continue until the underlying issue is addressed.

Your cycle does not have to become perfectly regular for treatment to be helpful. Goals may include reducing bleeding, treating pain or anaemia, supporting fertility, or making periods easier to manage.

Return for follow-up if symptoms worsen, treatment is not helping, or your bleeding pattern changes again.

Can I become pregnant if my periods are irregular?

Yes. Irregular periods can make ovulation harder to predict, but they do not mean pregnancy is impossible. Take a pregnancy test if your period is late and pregnancy could be possible.

Do irregular periods mean I have PCOS?

Not necessarily. PCOS is one possible cause, but many other situations can change cycles. Diagnosis usually considers symptoms, hormone patterns, and sometimes ultrasound findings.

Can contraception make periods irregular?

Yes. Irregular spotting, lighter bleeding, or no bleeding can occur with hormonal contraception. Speak with a healthcare professional if the change is difficult to manage, begins after a previously stable pattern, or comes with pain or pregnancy symptoms.

Is a missed period always a concern?

One missed period can occur with pregnancy, stress, illness, changing weight, exercise, or hormonal contraception. Test for pregnancy when relevant. Arrange an appointment if periods remain absent for three months without a known reason.