"I'm not having periods," "They last too long," "The amount is too heavy" or "too light." In the clinic, truly many people come in with worries about their periods. Yet often the standard of "what is a normal period" is held leaning on each person's own experience. When the standard is blurry, it is also hard to gauge what is abnormal. So today I want to first organize the range of normal menstruation, and from there look together at how it is good to view bleeding that deviates from it.
Normal menstruation, divided into four
When judging whether menstruation is normal, rather than vaguely "heavy/light," dividing it along four axes makes it much clearer. The International Federation of Gynecology and Obstetrics (FIGO) recommends describing menstruation by four elements: cycle, regularity, duration, and amount (FIGO 2018).
- Cycle: the interval from the start day of menstruation to the next start day, with roughly the 24–38 day range considered normal.
- Regularity: a state in which the difference between the shortest cycle and the longest cycle is not large is called regular.
- Duration: the number of days bleeding lasts, commonly around 4–6 days, and if it exceeds 8 days it is assessed as long.
- Amount: if it is not to the degree of hindering daily life or causing anemia, it is generally within the normal range.
In the past, the cycle was sometimes taught as 21–35 days, and you may still encounter this standard in various places in the text. FIGO's refining it to 24–38 days in the 2018 revision is the result of reflecting more data. Rather than memorizing the numbers themselves, it is more practical to look at "is my cycle maintained consistently."
Amount and duration, up to where is a sign to check
Menstrual amount is the item hardest to gauge on one's own. From clinical experience, a considerable number of complaints of "it seems heavy" mix cases that actually need checking with cases that do not. FIGO and the UK's NICE view the impact on daily life as a more important measure than absolute milliliter figures (NICE NG88, 2018·2021 revision). If there are signs like the following, I recommend looking into it at least once.
If you have to change a pad or tampon every one or two hours, or large clots repeatedly appear, or going out·sleep·work becomes difficult because of your period, we view it as a sign that the amount is heavy.
Duration is the same. If it goes beyond 8 days and continues long, or conversely a change occurs where it suddenly stops within a few days, more than the thing itself, the point "it has changed from usual" is the clue. If dizziness, easy fatigue, or paleness accompany it, it is good to also check the possibility of anemia. If such changes recur, you may also refer to the Abnormal vaginal bleeding symptom guide to gauge when to seek care.
Organizing the types of abnormal uterine bleeding
Bleeding that deviates from the normal range is collectively called abnormal uterine bleeding. Put in expressions patients often use, it is as follows.
| Type | What patients commonly say | What state it is |
|---|---|---|
| Heavy menstrual bleeding | "The amount is too heavy and clots come out" | When bleeding is heavy enough to hinder daily life |
| Oligomenorrhea | "I have it once every two or three months" | When the cycle interval has become excessively long |
| Frequent menstruation | "It seems I have it twice a month" | When the cycle interval has become excessively short |
| Intermenstrual bleeding | "It spots even when it's not a period" | Bleeding at a time other than the menstrual period |
For reference, there is also drug-related bleeding, like spotting in the early period of using hormonal contraceptives or bleeding that appears after stopping a progestin-class drug. In this case, telling us the drug you are using makes interpretation much easier. You can also see detailed patterns together in the Menstrual irregularity guide.
내 생리 패턴이 정상인지 물어보기Common causes, divided by PALM-COEIN
The causes of abnormal uterine bleeding seem diverse, but the International Federation of Gynecology and Obstetrics organizes them into a framework called PALM-COEIN (Munro, FIGO 2011·2018 revision). Even though it looks complex, the core is simple. It divides into structural causes that are "visible to the eye" by ultrasound or biopsy (PALM), and causes that are "not visible by structure," like hormonal·systemic states (COEIN).
- PALM: endometrial polyp, adenomyosis, uterine fibroid, and—rare but must absolutely be ruled out—malignant·premalignant changes of the endometrium.
- COEIN: coagulopathy, ovulatory dysfunction, problems of the endometrium itself, iatrogenic factors such as drugs, and cases not yet classified.
In the clinic, cases caused by ovulatory dysfunction are not uncommon. Factors that shake the ovulation rhythm, such as stress, weight change, and thyroid dysfunction, can be in the background, so it is better not to pass off intermenstrual bleeding or oligomenorrhea simply as "being sensitive." If thyroid or hormones are suspected, we check together with a blood test.
Uterine fibroids·polyps can occur even if you are unmarried or have no childbirth experience. Rather than "I'm young so it'll be fine," if the pattern has clearly changed, checking once is more reassuring.
Polycystic ovary syndrome (PCOS) likewise becomes a common background for oligomenorrhea through chronic anovulation. However, since PCOS requires separate depth in diagnostic criteria and management and is dealt with separately in the PCOS comprehensive management program guide, here I will only note it as "one of the representative causes of ovulatory dysfunction."
What is checked in the clinic
What is done in the clinic when the bleeding pattern has changed is, unexpectedly, simple. First we ask sufficiently, then add the necessary tests, in that order. A record of the last several months' cycles is a great help in grasping the pattern.
- History-taking: since when and how it changed, the drugs being taken, the possibility of pregnancy, accompanying symptoms.
- Imaging tests: pelvic ultrasound exam guide that examines structural causes.
- Blood tests: anemia, thyroid, and if needed the hormone panel test guide.
The approach differs according to the cause. When there is no structural problem, as in ovulatory dysfunction, drugs are sometimes used aiming at cycle recovery and anemia correction, and if a polyp or fibroid is confirmed, we discuss accordingly. If it is a concern intertwined with contraception or pregnancy plans, we can organize it together in the Pregnancy·contraception clinic guide. In any case, the cost is informed after consultation, so feel free to ask first without burden.
Normal vs. needs checking, compared at a glance
If I organize the complex content, it divides like this. You may also gauge your own state using the table below as a reference point.
| Item | Mostly normal | A sign that checking is advised |
|---|---|---|
| Cycle | Consistently 24–38 day interval | Skipping two or more months, or twice a month |
| Duration | Within 8 days | Exceeding 8 days, or abruptly shortened |
| Amount | No hindrance to daily life | Changing every one or two hours, large clots, dizziness |
| Bleeding outside the cycle | None | Repeated bleeding at a time other than the period |
If a change corresponding to the right side of the table continues for one or two months or more, that is a good time to receive a medical visit once. If menstrual pain is severe or irregularity is present together, you can also refer to the Menstrual pain·menstrual irregularity guide.
Menstruation is a bothersome thing that comes every month, but at the same time it is also the most honest signal the body sends. These days tools that help with recording, like period apps, are well made, so just consistently writing down your cycle makes a big difference. When you notice something different from usual, rather than only growing the worry "is this strange?" alone, please ask lightly through consulting comfortably about menstrual changes. We always cheer for the health of our elegant friends.
Written by: Lee Dong-hee Director · Obstetrics and Gynecology Specialist · View doctor profile
First published April 13, 2021 · Last reviewed May 30, 2026
References: FIGO PALM-COEIN classification (Munro, 2011·2018), ACOG abnormal uterine bleeding clinical guideline (2012, reaffirmed), NICE heavy menstrual bleeding guideline NG88 (2018·2021), Korea Disease Control and Prevention Agency National Health Information Portal Abnormal Uterine Bleeding (2023)
This article is intended to provide general health information and does not replace individual diagnosis or treatment. If you have symptoms, please consult through a medical visit.