A late period can send your mind racing: pregnancy, PCOS, thyroid, or something worse? Many women in India search for it simply as “periods time par nahi aana”. Irregular periods are common, and most causes are treatable.
For what PCOS is (now also called polyendocrine metabolic ovarian syndrome (PMOS)), how it is diagnosed and how it is treated, see our PCOS hub on symptoms, tests and treatment.
What counts as a normal cycle, and what counts as irregular periods
Count your cycle from the first day of one period to the day before the next one starts. National Health Service (NHS) says the average cycle is around 28 days and that periods are irregular if the gap is less than 21 days or more than 35 days. Irregular periods are not usually a sign of a problem, NHS adds, but are worth a GP visit.
The 2023 international PCOS guideline, which the hub follows, defines irregular cycles by how long ago your periods started:
| Time since your first period | Counts as irregular |
|---|---|
| First year | Nothing: irregular cycles are normal while the body settles |
| 1 to 3 years | Cycles shorter than 21 days or longer than 45 days |
| 3 years until perimenopause | Cycles shorter than 21 days or longer than 35 days, or fewer than 8 periods a year |
| Any time after the first year | Any single cycle longer than 90 days |
Fewer than eight periods a year counts as irregular, even if you never go three months without one. When cycles are irregular, the guideline says PCOS should be considered and assessed. Considered, not assumed: other causes come first.
Where the guidelines draw the line differently
International Federation of Gynecology and Obstetrics (FIGO), calls cycles of 24–38 days normal for women aged 18–45. It also expects your shortest and longest cycles to differ by no more than 9 days at ages 18–25 and 42–45, and 7 days at 26–41. FIGO calls bleeding for up to 8 days normal; NHS advises seeing a GP if periods last longer than 7 days.
So a 37-day cycle is normal to FIGO but irregular to the PCOS guideline and NHS. For the PCOS question, this page follows the PCOS guideline, as the hub does, because doctors use it to diagnose PCOS. Your doctor looks at your whole pattern, not one number.
A regular cycle is reassuring but not proof. The guideline notes that ovulation problems can occur with regular cycles; a blood test can check if it matters, for example when trying to conceive.
Irregular periods are not always PCOS: what else to check
PCOS is a common cause, but doctors rule out look-alikes first. NHS lists pregnancy, hormonal contraception, big weight changes, stress, too much exercise and the start of menopause as common causes, alongside PCOS and thyroid problems.
| Possible cause | Clues | What to check |
|---|---|---|
| Pregnancy | Any sex without reliable contraception, even once; breast tenderness or nausea | A home pregnancy test first, every time |
| Breastfeeding | Periods absent or irregular while you are feeding | Often expected; ask your doctor about contraception while feeding |
| Hormonal contraception | Started, changed or stopped the pill, injection or hormonal coil (IUS) | Ask the prescriber what bleeding pattern to expect; do not stop a method yourself |
| Thyroid problems | Tiredness or weight change | Thyroid-stimulating hormone (TSH) blood test |
| High prolactin | Milky nipple discharge when not pregnant or breastfeeding; headaches or vision changes | Prolactin blood test |
| Stress | Exams, a move, a wedding, a bereavement, long night shifts | See a doctor if periods stay irregular over several months |
| Big weight change | Sudden weight loss, or being overweight | Your weight and waist trend; our body mass index (BMI) calculator with Indian cut-offs gives a starting number |
| Too much exercise or too little food | Intense training, long fasts, very low body fat | A doctor can check hormone levels (LH and follicle-stimulating hormone (FSH)) |
| Perimenopause | Age in your 40s, cycles changing, hot flushes or poor sleep | A doctor’s review of your pattern; see our guide to perimenopause symptoms in your 40s |
| PCOS | Long gaps from your teens or early 20s, with acne, excess facial or body hair, or weight gain | A doctor’s assessment using the guideline criteria |
NHS adds that periods can stop with conditions such as heart disease, diabetes or an overactive or underactive thyroid. MedlinePlus notes that an underactive thyroid and some medicines can raise prolactin, and stress, exercise and even sex can cause small rises, so a slightly high result may be repeated.
Periods that stop after dieting or heavy training are a warning sign, not proof that a diet is working. The guideline says eating disorders should be considered in PCOS regardless of weight, especially during weight-loss efforts.
Why long gaps between periods matter: protecting the womb lining
Long gaps matter because of the womb lining (endometrium). In PCOS, when you do not ovulate, the lining is exposed to oestrogen without the progesterone that normally follows ovulation. National Institute for Health and Care Excellence (NICE)’s clinical summary for UK doctors says this could lead to abnormal bleeding, thickening of the lining (endometrial hyperplasia) and cancer.
The international PCOS guideline puts it this way:
- Women with PCOS have a “markedly higher risk” of endometrial hyperplasia and endometrial cancer before menopause. The evidence behind this is rated very low certainty.
- The overall chance of endometrial cancer is low, so routine screening is not recommended.
- “Long-standing untreated amenorrhoea” (going without periods), higher weight, type 2 diabetes and a persistently thick lining add to the risk.
- Women should be told about prevention: weight management, cycle regulation and regular progestogen therapy (a progesterone-like hormone).
UK guidance is more specific. NICE’s summary, drawing on the Royal College of Obstetricians and Gynaecologists (RCOG), says that in PCOS, gaps of more than 3 months, equivalent to fewer than four periods a year, may predispose to endometrial hyperplasia and later cancer. RCOG calls it “good clinical practice” to bring on a bleed at least every 3–4 months. That is consensus advice, not a trial result, and there is no evidence on which method works best.
What this means for you: if you have gone three months or more without a period and you are not pregnant, book a doctor’s review. A doctor may suggest hormone tablets taken for some days to bring on a bleed, the combined pill or a hormone-releasing coil, depending on your goals. Never take tablets to “bring on periods” from a chemist without a prescription; pregnancy has to be ruled out first. Healthy eating, activity and sleep help, but they cannot promise regular periods or replace treatment to protect the womb lining.
If you are 40 or over
Indian and international advice differ here. The Indian Menopause Society’s 2026 guideline recommends a sample of the womb lining (endometrial biopsy) for all women aged 40 or over with abnormal uterine bleeding. It cites Indian data: among such women, about 25% have endometrial hyperplasia (an overgrown lining) and 4–6% have cancer. NICE, for heavy periods, suggests a biopsy more selectively, for higher-risk women, including those with infrequent heavy bleeding who are obese or have PCOS. For Indian women over 40, we suggest the Indian guideline, because it is based on Indian patients. That is our judgement; your gynaecologist decides.
Tests a doctor may do for irregular periods
Most tests are simple blood tests, often after a urine pregnancy test. The hub’s diagnosis and tests section explains each one. In short, a doctor may:
- take your period history and check weight, waist, blood pressure, skin and hair;
- order thyroid-stimulating hormone (TSH), prolactin, FSH and 17-hydroxyprogesterone (17-OH progesterone) to rule out look-alikes, and testosterone if androgen excess is unclear;
- arrange a pelvic ultrasound in adults if needed, which can also show the lining’s thickness. The guideline says a scan is not needed for diagnosis when you have both irregular cycles and signs of androgen excess;
- order a full blood count, which NICE advises for every woman with heavy periods.
MedlinePlus says prolactin is usually tested three to four hours after waking, because levels change through the day. Tell your doctor about every medicine and supplement you take, and never stop one to be tested unless advised.
Tracking your periods at home
A written record is the most useful thing to bring to an appointment. NHS suggests an app or a diary; a wall calendar or your phone’s notes work too. For each period, note:
- the start date (Day 1) and how many days you bled;
- how heavy it was: how many pads a day, whether you soaked through or passed clots;
- any spotting between periods or after sex;
- pain, and anything else new, such as acne, hair growth, weight change or tiredness.
To find your cycle length, count the days from one Day 1 to the next. For example, a period that starts on 3 March followed by one on 12 April is a 40-day cycle. Three to six months of records give a clearer picture than memory.
If you cannot tell when a period is due, you can still test for pregnancy. NHS advises testing at least 21 days after you last had unprotected sex. A positive result is almost always right; a negative one is less reliable, so repeat it after a few days if your period still has not come.
Heavy bleeding after a long gap
FIGO notes that bleeding from ovulation problems is typically irregular in timing and flow, so a period after a long gap may be heavy. NHS lists PMOS among the causes of heavy periods and describes them as:
- changing a pad every 1 to 2 hours, or needing a pad and a tampon together;
- bleeding for more than 7 days;
- passing clots larger than about 2.5 cm;
- bleeding through to clothes or bedding, or missing work or college because of periods;
- feeling tired or short of breath a lot, which can mean anaemia.
Some heavy bleeding is an emergency (see below).
When to see a doctor
The hub has the full list of PCOS warning signs.
Emergency: get help now (call 112)
- Bleeding that soaks through a pad soon after you put it on, or heavy bleeding with dizziness, feeling faint or fainting.
- If you could be pregnant: severe or one-sided lower tummy pain, pain in the tip of your shoulder, fainting, or heavy bleeding. These can signal an ectopic pregnancy (outside the womb) or a miscarriage; NHS advises getting help even without a positive test.
Prompt review: within days to a few weeks
- No period for three months or more when you are not pregnant.
- A missed period when you could be pregnant: take a test, and see a doctor if it is positive or you are unsure.
- Heavy periods as described above, or bleeding between periods or after sex.
- Milky nipple discharge when not breastfeeding, or new headaches with vision changes.
- Facial or body hair that worsens quickly, or a deepening voice.
- Periods that stopped after dieting, fasting or heavy training, or fear and guilt around food.
Routine review
Book an appointment if your cycles are regularly shorter than 21 or longer than 35 days, you have fewer than eight periods a year, your usual pattern has changed, or you are trying to conceive and your periods are irregular.
How Disha can help
Disha is an AI health coach that chats and calls in Hindi, English and Hinglish. It does not replace a doctor, and it does not diagnose, prescribe or provide emergency care. It helps with the daily habits your doctor recommends: meals, movement, sleep and stress. Its onboarding call of about 15–20 minutes is conducted by Disha, the AI; no human doctor is on the call. Read how Disha coaching works.
This is not medical advice. This page is general education for adults (18+), not a diagnosis or treatment plan. Do not start, stop or change any medicine, including contraception, because of it. If you are pregnant, breastfeeding or have a current or past eating disorder, get individual advice. In an emergency, call 112.
Frequently asked questions
What counts as an irregular period?
For adults whose periods started more than three years ago, the international PCOS guideline counts cycles shorter than 21 days or longer than 35 days, fewer than eight periods a year, or any single cycle over 90 days. NHS uses the same 21 and 35 days. FIGO, the gynaecologists’ federation, calls 24–38 days normal. One odd cycle is common; a repeated pattern is worth a doctor’s review.
Do irregular periods always mean PCOS?
No. Pregnancy, breastfeeding, hormonal contraception, thyroid problems, high prolactin, stress, big weight changes, too much exercise and perimenopause can all cause irregular periods. That is why doctors do a pregnancy test and blood tests such as TSH and prolactin before diagnosing PCOS. PCOS diagnosis needs a combination of features, not irregular periods alone.
How long can I go without a period before I should worry?
First, take a pregnancy test if there is any chance you could be pregnant. If you are not pregnant, see a doctor after three months without a period. UK guidance says gaps of more than three months may thicken the womb lining in PCOS, and the international guideline lists long-standing untreated absence of periods as a risk factor. A doctor can offer treatment to protect the lining.
Can stress make my periods late?
Yes. NHS lists stress and anxiety among the common causes of late or irregular periods, alongside big weight changes and too much exercise. A stressful month can delay one period. If your periods stay irregular for several months, or stop for three months, see a doctor rather than assuming it is stress, because thyroid, prolactin or PCOS may need checking.
Should I take tablets to bring on my period?
Only if a doctor prescribes them after ruling out pregnancy. Hormone tablets, the combined pill or a hormone-releasing coil can protect the womb lining when periods are infrequent, and the right choice depends on your goals, such as contraception, acne or planning a baby. Do not buy tablets over the counter to “bring on periods”, and do not stop a prescribed one without advice.
Can I get pregnant if my periods are irregular?
Yes, you can. NHS says pregnancy can be harder with irregular periods because you may not release an egg regularly. You may still release one in some months, so use contraception if you do not want to conceive. If you are trying, NHS suggests sex every 2 or 3 days through the cycle, and a doctor can refer you for tests if it is not happening.
How do I track my periods properly?
Write down the first day of each period (Day 1), how many days you bled, how heavy it was and any spotting between periods. Your cycle length is the number of days from one Day 1 to the next. An app, diary or calendar all work, as NHS suggests. Bring three to six months of records to your appointment; they help a doctor more than memory does.
Sources
- Teede HJ, Tay CT, Laven JJE, Dokras A, Moran LJ, Piltonen TT, Costello MF, Boivin J, Redman LM, Boyle JA, Norman RJ, Mousa A, Joham AE. Recommendations From the 2023 International Evidence-based Guideline for the Assessment and Management of Polycystic Ovary Syndrome. Journal of Clinical Endocrinology and Metabolism, 2023. Supports: irregular-cycle definitions by years since the first period; considering PCOS when cycles are irregular; ovulatory dysfunction with regular cycles; tests to exclude other causes and low body fat or intensive exercise as a cause; no scan needed with irregular cycles and androgen excess; endometrial hyperplasia and cancer risk, low overall chance, no routine screening, risk factors and prevention; eating disorders regardless of weight.
- Munro MG, Balen AH, et al., for the FIGO Committee on Menstrual Disorders and Related Health Impacts and the FIGO Committee on Reproductive Medicine, Endocrinology, and Infertility. The FIGO Ovulatory Disorders Classification System. Human Reproduction, 2022; and Munro MG, et al. 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 and Obstetrics, 2018. Supports: normal frequency of 24–38 days for ages 18–45; shortest-to-longest variation of 9 or 7 days by age; normal duration up to 8 days.
- NHS. Irregular periods and Missed or late periods. Current patient guidance. Supports: the 28-day average and the 21- and 35-day limits; tracking with an app or diary and counting from Day 1; common causes including pregnancy, contraception, weight change, stress, exercise, breastfeeding, perimenopause and PMOS; thyroid disease, heart disease and diabetes; seeing a GP for periods longer than 7 days or bleeding between periods; harder conception and sex every 2 or 3 days.
- NHS. Polyendocrine metabolic ovarian syndrome (PMOS). Current patient guidance. Supports: PMOS as the new name for PCOS; irregular periods or long gaps as a main symptom; womb cancer among possible complications.
- NICE Clinical Knowledge Summaries. Polycystic ovary syndrome: management in adults and complications. Last revised March 2025. Supports: oestrogen exposure without progesterone in untreated anovulation; gaps of more than 3 months (fewer than four periods a year) and endometrial hyperplasia; RCOG’s good-practice advice to induce a bleed at least every 3–4 months, and no evidence on the best method; treatment options by category.
- NHS. Heavy periods. Current patient guidance. Supports: signs of heavy periods (a pad every 1 to 2 hours, more than 7 days, clots larger than 2.5 cm, bleeding through, tiredness or breathlessness); PMOS as a cause; seeing a GP for bleeding between periods or after sex.
- National Institute for Health and Care Excellence. Heavy menstrual bleeding: assessment and management (NG88). 2018, updated since. Supports: a full blood count for all women with heavy periods; endometrial biopsy considered for higher-risk women, including those with infrequent heavy bleeding who are obese or have PCOS.
- Meeta M, Anuradha M, Ashraf AB, Aggarwal K, Digumarti L, Singh T. Clinical Practice Guidelines for Menopause: An Executive Summary and Recommendations: Indian Menopause Society 2026. Journal of Mid-life Health, 2026. Supports: endometrial biopsy for all women aged 40 or over with abnormal uterine bleeding; Indian figures of 25% hyperplasia and 4–6% cancer in that group.
- MedlinePlus (US National Library of Medicine). Prolactin Levels. Current medical test information. Supports: symptoms of high prolactin in women, including irregular periods and breast milk production; causes including prolactinoma, medicines and underactive thyroid; small rises with stress, exercise and sex; testing three to four hours after waking; telling the provider about medicines.
- NHS. Doing a pregnancy test, Ectopic pregnancy and Vaginal bleeding in pregnancy. Current patient guidance. Supports: testing at least 21 days after unprotected sex when a period date is unknown; reliability of positive and negative results; one-sided tummy pain, shoulder-tip pain, bleeding and fainting as ectopic warning signs, and seeking advice even without a positive test; heavy bleeding that soaks a pad soon after putting it on, and feeling faint or dizzy, as reasons for emergency care.
Related reads
- PCOS in India: symptoms, tests, treatment and daily care: the overview this page sits under. It covers diagnosis, each test and treatment in full.
- PCOS diet in India: a practical plate for every meal: the Indian plate, example days and diet myths, for readers whose doctor has confirmed PCOS.
- Why weight loss feels harder with PCOS, and what actually helps: for readers at a higher weight who want to lose some safely.
- Perimenopause symptoms in your 40s: for women over 40 whose cycles are changing.
- All PCOS articles: every Disha guide on PCOS in one place.
- BMI calculator with Indian cut-offs: weight change can affect periods. BMI is a screening number, not a test for PCOS.
