Missed period and late periods: causes, testing and when to be seen

A period that has not arrived on the day it was expected is one of the commonest reasons people start searching for answers about their own cycle, and the first question is almost always the same one. This article deals with that question first, because it is the one with a clear test attached to it. After that, the honest position is that cycle length varies a good deal between healthy women, and within the same woman from one month to the next, so bleeding that arrives a few days later than usual is often ordinary variation rather than a sign of anything wrong.

What follows sets out how and when to use a pregnancy test, and what a negative result does and does not rule out. It then defines what counts as late rather than variable, using the normal range of cycle length, and works through the causes: late ovulation and why it moves everything after it, stress and illness, weight change and heavy exercise, polycystic ovary syndrome, thyroid disease, raised prolactin, perimenopause, recent hormonal contraception or stopping it, and breastfeeding. It also sets out when absent periods become worth investigating, what that assessment involves, and which findings need to be seen the same day.

Pregnancy first: how and when to test

For anyone who could be pregnant at all, the first step is a urine pregnancy test rather than a search for other explanations. These tests detect human chorionic gonadotrophin, usually written as hCG, which is produced once an embryo has implanted and which rises steeply in the days afterwards. Most home tests are designed to pick up hCG at around 20 to 25 mIU/mL in urine, although some early detection kits are labelled as sensitive to about 10 mIU/mL and the figure is printed in the instructions, which is why the timing of the test matters as much as the test itself. NHS information says a sample collected at any time of day can be used and that it does not have to be the morning. First morning urine is the most concentrated, so it is the sample several manufacturers prefer when a test is done early, and it is the better choice for a repeat test taken before the period is clearly overdue.

Guidance on timing differs in emphasis. NHS information says most tests can be used from the first day of a missed period, and that some more sensitive tests can be used a few days before that. Most manufacturers advise waiting until the day the period is due, or about a week after, because a test done earlier can be negative in a pregnancy that is simply too early to show. NHS information adds that if you do not know when your next period was due, you should test at least 21 days after you last had unprotected sex. Both positions are reasonable, and both give the same practical advice: an early negative result is worth repeating. Our article on how soon you can take a pregnancy test covers the timing.

A quantitative blood test for hCG, done in a laboratory, becomes positive a little earlier than a urine test and is reported as a number in mIU/mL. It is not routinely needed to answer the question of whether someone is pregnant when a urine test can be repeated instead, and in early pregnancy the pattern of change between two samples taken a few days apart usually says more than a single value. In early pregnancy hCG roughly doubles every two to three days, which is why a repeat is informative. Your own doctor decides whether a blood test adds anything in your situation.

Findings that need assessment the same day

Almost every late period described on this page has an ordinary explanation and needs nothing more than a repeat test or a few cycles of watching. A small number do not, and those belong near the beginning rather than buried at the end, because the interval between a symptom starting and being assessed is what changes how it turns out. The findings below are the ones to act on today rather than waiting for the next cycle, a repeat test or a routine appointment.

• Pain low in the abdomen, especially on one side, or any bleeding or brown watery discharge, in anyone whose period is late and who could be pregnant: this needs assessment the same day, whether the pregnancy test is positive, negative or has not been done, because an ectopic pregnancy has to be excluded before anything else is assumed. NHS advice is to seek help right away even without a positive pregnancy test.
• Sudden, sharp or severe abdominal pain, pain in the tip of the shoulder, feeling very dizzy or faint, collapsing, feeling sick or looking very pale, in anyone whose period is late: call your local emergency number (112 in Turkey and across the EU, 999 in the UK, 911 in the US) rather than arranging an appointment, and do not wait to do a pregnancy test first, because a ruptured ectopic pregnancy is a surgical emergency.
• Absent or stopped periods together with a severe or unfamiliar headache, or with any change in vision such as blurring, double vision or loss of the outer edges of the visual field: this needs to be assessed the same day, because the pituitary gland sits directly beneath the nerves that carry vision.
• Absent periods with milky discharge from the breasts when not breastfeeding, if there is also headache or any visual change: the same applies, and it should not wait for a blood test appointment.
• A late period with fever, with pelvic pain, or with unusual discharge, in any combination, or pain severe enough to stop you standing up straight: this needs to be assessed the same day rather than watched, because pelvic infection does better the earlier treatment is started.

None of these patterns is improved by waiting to see whether bleeding starts. If a pregnancy test is positive and there is pain or bleeding, the test result is not reassurance, it is the reason to be seen. A negative test is not reassurance either when pain is one sided, severe or getting worse, because a very early pregnancy and an ectopic pregnancy can both test negative; the pain is the reason to be seen. If periods have stopped and there is headache or a change in vision, that combination is what matters, not how long the periods have been absent. Pain without bleeding has its own set of explanations, which are covered in our article on cramps with no period.

What counts as late, and what is simply variation

Cycle length is counted from the first day of proper bleeding to the day before the next period starts. Day one is the first day of real flow, not the first day of brown spotting, and keeping that distinction makes cycles comparable from month to month. Within one woman, a few days of movement either side of her usual length is normal, and the length of the cycle that follows an illness, a long flight or a difficult few weeks is often the one that drifts. A period is reasonably called late when it has not arrived by the day expected from a pattern that was previously predictable.

The outer limits of normal are described differently by different bodies, which is worth knowing if you have compared two sources and found they disagree. The specialist classification used for abnormal uterine bleeding puts the usual range at 24 to 38 days, while the NHS and ACOG patient information cited at the end of this article both use 21 to 35 days. On either definition, a cycle that sits inside those limits is not abnormal on length alone, and a woman whose cycles have always run to the longer end of the range is not having late periods, she is having her own periods.

One late period, with a negative test and nothing else going on, is the commonest situation of all and rarely turns out to represent disease. What carries more information is a change in your own pattern that persists: cycles that were regular and are now unpredictable, cycles that keep lengthening, or periods that stop altogether. That is a pattern to take to your own doctor, who can read it against your age, your history and your examination in a way that no article can.

Late ovulation, and why it moves everything after it

The cycle has two halves and they are not equally flexible. The first half, from day one until ovulation, varies in length because it depends on how long a follicle takes to mature. The second half, from ovulation until bleeding starts, is comparatively fixed, most often twelve to fourteen days and usually within the ten to sixteen day range NHS information gives, because it is set by the lifespan of the corpus luteum. The practical consequence is that, once pregnancy has been excluded, a late period is commonly just a period that follows a late ovulation. Nothing has gone wrong with the womb, and the delay has already happened weeks before the date that was being watched.

This also explains why cycle tracking applications so often predict a date that does not arrive. Most of them work from the average of previous cycles and assume ovulation happened on schedule, so a cycle in which ovulation came a week late shows as a period that is a week overdue. It matters for testing too: hCG only starts to rise after implantation, so if ovulation was late, a test on the predicted date can be genuinely too early. Repeating the test after a few days answers this better than any amount of calculation.

What delays ovulation is usually something in the weeks beforehand rather than anything happening now. An infection with a fever, a course of illness, several short nights, a change of time zone, a stretch of unusual physical or emotional load, or a sudden change in eating or training can all postpone the hormonal surge that releases the egg. In most women the cycle resets by itself over the following month or two. If ovulation is repeatedly late, so that cycles run long month after month, that is the pattern worth taking further.

Stress, illness and a disrupted routine

The signal that drives the whole cycle starts in the hypothalamus, which releases gonadotrophin releasing hormone in pulses. Those pulses are sensitive to the body's general situation, and they slow when the brain reads the circumstances as unfavourable. That is why a bereavement, examinations, a demanding period at work, a move or any sustained strain can push a period back or make it skip, with no abnormality anywhere in the ovaries or the womb. The mechanism is the same one that produces an absent period in illness, and it recovers in the same way, by removing the load rather than by treating the cycle.

Acute illness does the same thing more sharply. A febrile infection, an operation, a hospital admission or a significant injury commonly delays the next period, and the cycle after the one that was disrupted usually returns to its own rhythm. Shift work and repeated changes of time zone are worth separating out, because the disruption is to sleep and light exposure rather than to mood, and the effect can persist for as long as the pattern does. Long haul travel in the week before ovulation is a common and usually harmless explanation for a cycle that runs long.

The limit of self management is where this becomes a pattern rather than an episode. One or two disturbed cycles after an identifiable event need no investigation. Periods that stay absent after life has settled, or that stop during a period of restricted eating or intense training, should be assessed rather than attributed to stress, because stress is a diagnosis that is reached after the others have been considered, not before. Your own doctor is the person to draw that line, and it is worth asking rather than waiting several more months.

Weight change, low energy availability and heavy exercise

The reproductive axis responds to how much energy the body has available, not simply to body weight. Rapid weight loss, restrictive eating, a very low carbohydrate or very low calorie regime, or an eating disorder can all suppress the hypothalamic pulses and stop periods, and this can happen at a weight that looks unremarkable from the outside. A body mass index below about 18.5 kg/m2 makes it more likely, but the deciding factor is the gap between energy taken in and energy used. Periods that have stopped for this reason are a signal from the body rather than a cosmetic problem.

Heavy training produces the same picture through the same route, particularly in endurance running, cycling, rowing, dance and gymnastics, and in anyone who has increased their volume sharply. The relevant idea is relative energy deficiency in sport, where intake has not kept pace with training load. Absent periods in this setting are not a sign of fitness and are not harmless, because oestrogen also maintains bone density, and bone lost in these years is difficult to recover. Anyone whose periods have stopped while training hard should raise it with a doctor rather than treating it as expected.

Weight gain can disturb cycles in the opposite direction, largely through insulin resistance, which alters the balance of hormones reaching the ovary and makes ovulation less regular. The pattern is usually infrequent rather than absent periods, and it overlaps considerably with polycystic ovary syndrome, discussed next. Management in all of these situations is directed at the cause rather than at the bleeding, and it is work done with a doctor and often a dietitian over months. Restoring energy availability is what restores the cycle, and it is the step that also protects bone.

Polycystic ovary syndrome (now also called polyendocrine metabolic ovarian syndrome)

Polycystic ovary syndrome, which NHS and MedlinePlus information now call polyendocrine metabolic ovarian syndrome, or PMOS, is among the explanations most often found when periods are habitually late rather than occasionally late. The two names describe the same condition, and ACOG and the international evidence based guideline still use the older one, so you will meet both. It is a hormonal pattern rather than a problem with the ovaries themselves, and it is recognised by any two of three features: cycles that are infrequent or absent because ovulation is unreliable, clinical or laboratory evidence of raised androgens, and a characteristic appearance of the ovaries on ultrasound. The cycles are the feature that brings most women to ask the question, often with a history of periods that were irregular from the start rather than periods that changed.

Assessment involves blood tests for androgens and for the hormones that exclude other causes, usually with thyroid function and prolactin, and an ultrasound scan in some circumstances. This is an area where guidance has genuinely moved and bodies differ: the international evidence based guideline advises against using ultrasound to make the diagnosis within about eight years of the first period, because the appearance is common at that age, and it accepts anti Mullerian hormone as an alternative to ultrasound in adults, while a good deal of older material and some national guidance still treat the scan as central. Both approaches are in use.

What matters for someone whose period is late is that the syndrome is a long term pattern to be managed rather than an emergency, and that the management is individual. It is directed at the symptoms that are actually present, at insulin resistance where it is found, and at the lining of the womb when periods are very infrequent. Fertility is a separate conversation, and it is covered in our article on PCOS and getting pregnant. The diagnosis should be made by your own doctor, because several conditions imitate it.

Thyroid disease and raised prolactin

The thyroid influences the cycle in both directions. An underactive thyroid tends to produce heavier or more frequent bleeding but can also make periods infrequent or absent, while an overactive thyroid more often makes them light and widely spaced. Both are easy to test for, with a thyroid stimulating hormone level and free thyroxine measured on a single blood sample, and both have other features worth mentioning to your doctor: changes in weight, bowel habit, temperature tolerance, hair, mood and energy. Treatment is prescribed and then monitored by a doctor, who adjusts it using repeat blood tests over months.

Prolactin is the other hormone to check. When prolactin is raised it suppresses the signals that drive ovulation, so periods become infrequent or stop, sometimes with milky discharge from the breasts. The causes are varied: a benign pituitary adenoma, an underactive thyroid, chronic kidney disease, nipple stimulation, pregnancy and breastfeeding, and several prescribed medicine classes including some antipsychotics, some antidepressants, some antiemetics and some blood pressure drugs. Stress, a recent meal or a difficult blood draw can all nudge the result upward, which is why a single raised value is repeated before anything is concluded from it.

Prolactin is reported in ng/mL or in mIU/L depending on the laboratory, and the reference range printed on your own report is the one that applies, because assays differ. A clearly raised and confirmed level usually prompts imaging of the pituitary gland. Headache or any change in vision alongside absent periods is the combination that needs same day assessment rather than a routine appointment, as set out above. Our article on high prolactin and fertility covers the assessment in more detail.

Perimenopause and the years when cycles change

From the late thirties onwards, and more noticeably through the forties, cycles begin to change because ovulation becomes less reliable. The earliest sign is usually a shift in cycle length rather than a change in flow: cycles shorten for a while in some women, then lengthen, and skipped periods appear. A period that goes missing and then returns is a characteristic feature of this phase, and it can repeat for a year or more. Hot flushes, night sweats, disturbed sleep and mood change may or may not accompany it, and their absence does not rule perimenopause out.

Two practical points follow. Pregnancy is still possible while periods are occurring at all, however irregular they have become, so contraception remains relevant until a doctor advises otherwise, and a late period in the forties still warrants a test. The second point concerns bleeding at the other end: once twelve consecutive months have passed with no bleeding, any bleeding that then occurs is postmenopausal bleeding and should be assessed promptly in its own right rather than counted as a period that returned. That is a separate pathway and your own doctor will arrange it.

Periods that become irregular or stop before the age of forty are a different matter and should not be put down to an early menopause without assessment. Premature ovarian insufficiency is diagnosed with repeated hormone tests rather than a single set, because values fluctuate, and it has implications for bone and cardiovascular health that are managed actively. Anyone under forty whose periods have stopped for several months, with or without hot flushes, should be assessed rather than reassured by age alone, and the assessment is straightforward.

Hormonal contraception, stopping it, and breastfeeding

Several methods of contraception make periods light, infrequent or absent by design, and this is an expected effect rather than a complication. The progestogen only implant, the injection, the progestogen only pill and the hormonal intrauterine system all thin the lining of the womb, and the hormonal coil in particular often reduces bleeding to occasional spotting or to nothing at all. With combined hormonal contraception, skipping the break or running packets together removes the withdrawal bleed in the same way. None of this stores up blood or harms the womb, and bleeding patterns often settle over the first several months.

After stopping, the time to the first proper period varies by method. Most women ovulate again within a few weeks of stopping a pill, a patch, a ring, an implant or a coil, and the first period follows soon after. The injection is the exception, because its effect wears off gradually and cycles can take several months or longer to return once the last dose has worn off. An important practical point: ovulation can happen before the first period arrives, so pregnancy is possible in that interval and a late period after stopping contraception still needs a test.

Breastfeeding suppresses ovulation through raised prolactin, and absent periods are expected while feeds are frequent, including through the night. The return is unpredictable and depends mostly on how often and how long the baby feeds, so periods often restart as feeds are spaced out, night feeds stop or solids begin. Lactational amenorrhoea is only a reliable method of contraception when strict conditions are all met, and most women do not meet them for long, so a late period while breastfeeding is still a reason to test rather than to assume.

When a late period becomes worth investigating

The point at which a missing period stops being a one off is defined in similar but not identical ways. NHS information advises seeing a GP if you have missed your period three times in a row and are not pregnant, and also if your periods have become irregular, if they have not started by the age of fifteen, or if they come with symptoms such as weight change, tiredness or new facial hair. ACOG material defines secondary absent periods as no period for three months or more, and advises assessment whenever periods stop for more than three months without explanation, while MedlinePlus uses a longer cut off of six months and applies it to women whose cycles had been normal; in practice the longer figure is used where cycles were already irregular. The thresholds set out in patient information therefore genuinely differ, and all of them agree that associated symptoms bring the appointment forward rather than delay it.

• You are trying to conceive, or you are over about thirty five and your cycles have become unpredictable: assessment is reasonable sooner rather than after months of waiting.
• Milky discharge from the breasts alongside periods that have stopped. If there is also a new or unfamiliar headache, or any change in vision, that combination needs same day assessment rather than an appointment, as set out above.
• Hot flushes, night sweats or vaginal dryness under the age of forty.
• Increasing facial or body hair, marked acne, hair loss at the temples, or a deepening voice, which point towards raised androgens.
• Periods that stopped after a uterine procedure, a retained placenta, a pregnancy loss or an infection of the womb, which raises the question of scarring inside the cavity.
• Periods that have never started by the age of fifteen, or no sign of breast development by thirteen.

Two further situations deserve their own mention. Periods that stop while weight is falling or training load is rising should be assessed at that point, not after a year, because of the effect on bone. And bleeding that becomes irregular, happens between periods or after intercourse, or occurs at all after the menopause, is assessed in its own right whatever the cycle is doing, because those are the patterns that prompt examination of the cervix and the lining of the womb. Your own doctor decides which of these applies to you.

What the assessment involves

Assessment starts with history and, usually, examination, and the single most useful thing to bring is a record of recent cycles: the first day of each of the last few periods, how long bleeding lasted, and anything that changed in the same months. A pregnancy test is repeated in the consultation if there is any possibility at all, because it is the one result that changes everything else. Beyond that, the tests chosen depend on the story rather than being done as a fixed panel, and timing from day one matters for some of them.

• Blood tests commonly used: follicle stimulating hormone and luteinising hormone, oestradiol, prolactin, thyroid stimulating hormone with free thyroxine, and testosterone where raised androgens are suspected.
• Anti Mullerian hormone in selected situations, usually when ovarian reserve or polycystic ovary syndrome is the question, rather than as a routine test for a late period.
• Pelvic ultrasound, which looks at the ovaries, the thickness of the lining and the shape of the cavity.
• Imaging of the pituitary gland when prolactin is confirmed as clearly raised, or when there are headaches or visual symptoms.
• A short course of a progestogen may be prescribed to see whether bleeding follows, which tells the doctor something about oestrogen levels and about the lining; what is used and for how long is a decision for the prescriber.

Where the first set of results is normal and the story points to energy availability, stress or a recent illness, the next step is often watching for a few cycles with a cycle record, rather than more tests. Where a cause is identified, treatment is directed at that cause: thyroid disease is treated as thyroid disease, raised prolactin as raised prolactin, and the cycle follows. Nothing here is a reason to take anything bought without a prescription, and dosing decisions belong with the doctor who knows your results.

It is worth ending on proportion. Most late periods are explained by pregnancy, by a late ovulation, or by something in the previous weeks that pushed ovulation back, and most resolve without any intervention. The situations that need prompt action are narrow and specific, and they are set out in the second section of this page for that reason. If a period is late and a test is negative, repeat the test after a few days, write the cycle down, and take the record to your own doctor if the pattern continues.

Related Reading

• Negative pregnancy test but no period: why it happens and when to be assessed
• PCOS and Getting Pregnant: Symptoms, Diagnosis and Fertility Options
• Does High Prolactin Affect Fertility?
• Cramps but no period: what causes it and when it needs assessing
• How soon can you take a pregnancy test? The timeline, day by day
• Decidual cast: passing tissue in one piece

Sources and references

This article is supported by the following independent, authoritative sources:

• NHS, Missed or late periods
• NHS, Doing a pregnancy test
• NHS, Ectopic pregnancy
• ACOG, Amenorrhea, absence of periods
• MedlinePlus, Absent menstrual periods, secondary
• ESHRE, International evidence-based guideline for the assessment and management of polycystic ovary syndrome