Periods are considered irregular when the length of your cycle keeps changing by more than about 7–9 days, cycles are shorter than 21 or longer than 35 days, or periods are skipped. Common causes include stress, weight change, PCOS, thyroid problems and perimenopause. Diagnosis usually involves a pregnancy test, ultrasound and hormone blood tests.
- Typical cycle
- 21–35 days in adults
- Common causes
- PCOS, thyroid, stress
- Tests
- Pregnancy test, ultrasound, blood
- Treatment
- Depends on cause and plans
- Results
- Blood tests in a few days
- Visit
- Walk-ins welcome
What counts as an irregular period?
A menstrual cycle is counted from the first day of one period to the first day of the next. In adults it is usually 21–35 days, and a few days' variation from month to month is normal. Your cycle may be irregular if:
- The gap between periods changes by more than about 7–9 days
- Cycles are regularly shorter than 21 days or longer than 35 days
- You miss periods for three months or more (see amenorrhea)
- You bleed between periods or after sex
Irregular cycles are common in the first years after periods start and in the years before menopause. Outside those stages, a persistent change deserves a check-up.
Common causes of irregular periods
| Cause | Clues | How it is checked |
|---|---|---|
| Pregnancy | Late or missed period, breast tenderness | Urine or blood pregnancy test |
| Polycystic ovary syndrome (PCOS) | Long cycles, acne, extra hair growth, weight gain | Ultrasound and hormone tests |
| Thyroid problems | Tiredness, weight change, feeling cold or hot | Thyroid blood test (TSH) |
| High prolactin | Missed periods, sometimes milky nipple discharge | Prolactin blood test |
| Stress, weight change, intense exercise | Recent move, exams, dieting, training | History; other causes ruled out |
| Perimenopause | Age 40s, hot flushes, sleep changes | History; hormone tests sometimes |
| Hormonal contraception | Spotting or light, unpredictable bleeds | Review of your method |
| Polyps or fibroids | Bleeding between periods, heavy bleeding | Pelvic ultrasound |
Moving to Korea, long-haul travel and a new job can all temporarily disturb ovulation. If your cycle does not settle within a few months, see a doctor. For a broader overview see hormonal imbalance.
How irregular periods are diagnosed at Yoonho
- Cycle history in English Your doctor asks about cycle dates, bleeding, weight, stress, medicines, contraception and pregnancy plans. Bring your period-tracking app data.
- Pregnancy test Done first when there is any chance of pregnancy.
- Pelvic ultrasound A same-day pelvic ultrasound looks at the ovaries and uterine lining, and for polyps or fibroids.
- Hormone blood tests Such as thyroid function, prolactin, FSH/LH and androgens, timed to your cycle when possible.
- Explaining the results Results are discussed in English with a written plan; an English report is available.
- Periods arrive unpredictably or are skipped
- Worry about pregnancy or fertility
- Spotting between periods
- No clear explanation for the change
- A likely cause identified with tests
- A plan that aims for more predictable bleeding
- Protection of the uterine lining
- Advice tailored to pregnancy plans
Treatment options
Treatment depends on the cause, your symptoms, and whether you want to become pregnant.
- Lifestyle support — regular meals, gradual weight change if advised, sleep and stress management can restore ovulation for some women, especially with PCOS.
- Hormonal contraceptives — combined pills, patches or a hormonal IUD can make bleeding predictable and protect the lining.
- Cyclic progestogen — for women who do not want contraception, to bring on regular bleeds and protect the uterine lining.
- Treating the underlying cause — for example thyroid medication or treatment of high prolactin.
- Ovulation support — if you are trying to conceive, medicines that help ovulation may be discussed; see preconception counseling.
Long gaps without periods are not just inconvenient: without regular shedding, the uterine lining can thicken over time, so it is worth treating even if you are not planning a pregnancy.
When to see a doctor
- No period for 3 months (and you are not pregnant)
- Cycles regularly shorter than 21 or longer than 35 days
- Bleeding between periods, after sex or after menopause
- Very heavy bleeding — see is my period too heavy?
- Irregular periods with acne, hair growth or difficulty getting pregnant
Cost and insurance
Consultations are generally around ₩50,000–100,000, with ultrasound and blood tests added depending on what is needed; this is a general guide, and a written estimate is given after consultation. Residents enrolled in National Health Insurance are usually covered for medically necessary tests — see health insurance for foreigners. Travelers can ask for English receipts for insurance claims.
Why international patients choose Yoonho
Frequently asked questions
Can moving to Korea make my periods irregular?
Yes. Travel, jet lag, a new job and changes in diet or sleep can temporarily disturb ovulation. If your cycle has not settled within about three months, get checked.
Does an irregular period mean I can't get pregnant?
Not necessarily. Many women with irregular cycles conceive, but irregular ovulation can make it take longer. If you are trying, see a doctor sooner rather than later.
Do I need hormone tests on a specific day?
Some hormone tests are most useful in the first days of your cycle, but others can be done any day. Your doctor will tell you if a second blood test should be timed.
Can I buy birth control pills to regulate my period in Korea?
Some combined pills are sold at pharmacies without a prescription, but it is safer to find the cause first and choose a pill with your doctor's advice.
Is PCOS diagnosed with ultrasound alone?
No. PCOS is diagnosed by combining cycle history, signs or blood tests showing higher androgens, and ultrasound findings, after other causes are excluded.
OB-GYN Specialist · Director of OB-GYN
M.D., Ewha Womans University College of Medicine · Former Clinical Instructor, Ewha Womans University Mokdong Hospital · Member, Korean Society of Menopause
Last reviewed: . This page is for general information and does not replace an in-person consultation.
Talk to an English-speaking gynecologist
Yoonho Hospital · 304 Apgujeong-ro, Gangnam-gu, Seoul · Mon–Fri 9:00–18:00, Sat 9:00–13:00 · Walk-ins welcome.