Period pain and irregular periods: what's normal, what helps, and when to worry

What a normal period looks like

The International Federation of Gynecology and Obstetrics (FIGO) defines a normal cycle as:

• Cycle length: 24 to 38 days, counted from the first day of one period to the first day of the next.
• Bleeding: up to 8 days.
• Regularity: the length can vary by up to 7 to 9 days from one cycle to the next.

So a 26-day cycle one month and a 32-day cycle the next is normal. “28 days” is an average, not a rule. Ovulation happens about 14 days before your next period, so in a 35-day cycle it’s around day 21, not day 14.

Why periods become irregular

If your period is late, take a pregnancy test first. After that, the most common causes are:

• PCOS. Irregular cycles together with acne, excess facial or body hair, or weight gain.
• Thyroid problems. Both an underactive and an overactive thyroid can change your cycle. A TSH blood test checks for it.
• Stress, low body weight, under-eating or very heavy exercise. These can switch off ovulation, and periods become irregular or stop.
• Life stage. Cycles are often irregular for a few years after periods start, and again in the years before menopause.

See a doctor if your periods stay irregular, stop for three months or more (and you’re not pregnant), or come with the PCOS signs above. Our guide to irregular, heavy or painful periods lists the tests a doctor will usually order.

PCOD vs PCOS: is there a difference?

You may hear both “PCOD” and “PCOS”. PCOD (polycystic ovarian disease) is an older term still used in some countries. Doctors and the 2023 international guideline use PCOS (polycystic ovary syndrome), and they describe the same condition.

In adults, PCOS is diagnosed when you have two of these three:

1. Irregular or absent periods.
2. Signs of higher male hormones: acne, excess hair growth, or a high level on a blood test.
3. Polycystic ovaries on an ultrasound, or a high AMH level on a blood test.

Two important points. Cysts on a scan alone do not mean you have PCOS. And because insulin resistance is common with PCOS, lifestyle changes (regular exercise, a balanced diet and, where needed, weight loss) are the first step. There are also effective medical treatments for specific symptoms such as irregular cycles, acne and hair growth.

What actually relieves period pain

Period cramps are caused by prostaglandins, chemicals that make the muscle of the womb contract. That explains why the most effective treatments work the way they do.

• Anti-inflammatory painkillers (NSAIDs) such as ibuprofen or mefenamic acid lower prostaglandins. A Cochrane review found they work well for most women. They work best taken when the pain starts, not after it peaks. Check with a doctor first if you have stomach ulcers, asthma that NSAIDs worsen, or kidney problems.
• Heat. A 2018 meta-analysis found that heat, such as a hot water bottle or heat patch on your lower belly, reduced period pain.
• Regular exercise. A Cochrane review found that exercising regularly through the month, not just during your period, may reduce period pain.
• Hormonal contraception reduces period pain for many women. Ask your doctor whether it suits you.

When period pain is not normal

Some period pain is common. Pain that takes over your life is not. See a gynaecologist if:

• the pain stops you going to work, college or school,
• painkillers don’t help,
• the pain is getting worse over the years,
• you have pain during or after sex, or when opening your bowels during your period.

These can be signs of endometriosis, where tissue similar to the womb lining grows outside the womb. It affects about 1 in 10 women of reproductive age, and diagnosis is often delayed for years because severe pain gets dismissed as “normal”.

Heavy periods drain your iron

Signs that your periods are heavier than normal:

• soaking through a pad or tampon every hour for several hours,
• passing large clots,
• needing to change protection during the night,
• bleeding for more than 8 days.

Heavy periods are one of the most common causes of iron deficiency in women. It can make you tired, breathless and less fit long before it shows up as anaemia. Ask for a ferritin test, not just haemoglobin. Our women’s health guide covers iron, thyroid and the screenings worth doing at each age.

See a doctor promptly for

• bleeding between periods or after sex,
• any bleeding after menopause,
• very heavy bleeding with dizziness or breathlessness,
• severe pain with fever, or sudden one-sided pain in your lower belly.

References

1. 1.The two FIGO systems for normal and abnormal uterine bleeding symptoms and classification of causes of abnormal uterine bleeding in the reproductive years: 2018 revisions. International Journal of Gynecology & Obstetrics, 2018.doi:10.1002/ijgo.12666
2. 2.Nonsteroidal anti-inflammatory drugs for dysmenorrhoea. Cochrane Database of Systematic Reviews, 2015.doi:10.1002/14651858.CD001751.pub3
3. 3.Exercise for dysmenorrhoea. Cochrane Database of Systematic Reviews, 2019.doi:10.1002/14651858.CD004142.pub4
4. 4.Heat therapy for primary dysmenorrhea: a systematic review and meta-analysis of its effects on pain relief and quality of life. Scientific Reports, 2018.doi:10.1038/s41598-018-34303-z
5. 5.Recommendations from the 2023 International Evidence-based Guideline for the Assessment and Management of Polycystic Ovary Syndrome. Journal of Clinical Endocrinology & Metabolism, 2023.doi:10.1210/clinem/dgad463
6. 6.Endometriosis. New England Journal of Medicine, 2020.doi:10.1056/NEJMra1810764
7. 7.Hypothyroidism. The Lancet, 2017.doi:10.1016/S0140-6736(17)30703-1
8. 8.Iron-deficiency anemia. New England Journal of Medicine, 2015.doi:10.1056/NEJMra1401038

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Educational information, not medical advice. See a doctor for anything persistent or severe. All content is original to Venva.