Irregular Menstruation
Menstrual cycles that vary in timing, length, or flow
Quick Facts
- Type: Menstrual / reproductive condition
- Means: Cycles vary in timing, length, or flow
- Common causes: Hormone changes, PCOS, thyroid, stress
- Normal cycle: Roughly 21 to 35 days
Overview
Menstrual cycles are considered irregular when they vary noticeably in their timing, length, or flow. A typical cycle runs about 21 to 35 days, counted from the first day of one period to the first day of the next. Periods that come much more or less often than this, that change unpredictably from month to month, or that vary greatly in heaviness or length may be described as irregular.
Some variation is normal, especially in the years after periods first begin and in the lead-up to menopause. At other times, irregular periods reflect a hormonal imbalance or an underlying condition. Tracking your cycles and noting other symptoms helps a clinician find the cause.
Symptoms
Irregular menstruation can show up in several ways:
- Cycles shorter than 21 days or longer than 35 days
- Cycle length that changes substantially from month to month
- Skipped periods
- Unusually heavy or light bleeding
- Periods that last much longer or shorter than usual
- Spotting or bleeding between periods
Associated symptoms such as acne, excess hair growth, weight change, fatigue, or pelvic pain may point to a specific cause. Bleeding after menopause, or very heavy bleeding, always needs evaluation.
Causes
Irregular periods have many possible causes:
- Natural hormone shifts: The first years after periods start and the years before menopause (perimenopause).
- Polycystic ovary syndrome (PCOS): A common hormonal cause of irregular or infrequent periods.
- Thyroid problems: Both overactive and underactive thyroid can disrupt cycles.
- Stress, weight change, and intense exercise.
- Hormonal contraception and other medications.
- Uterine conditions such as fibroids or polyps, which can affect bleeding.
- High prolactin levels and other hormone imbalances.
Risk Factors
- Adolescence and perimenopause
- Polycystic ovary syndrome or thyroid disease
- Significant weight gain or loss
- High stress and intense physical training
- Use of certain hormonal contraceptives or other medications
- Uterine fibroids or polyps
Diagnosis
Evaluation begins with a history of your cycles and any related symptoms, plus an examination. Tests may include:
- Pregnancy test, since pregnancy can change bleeding patterns.
- Blood hormone tests, including thyroid hormone, prolactin, and reproductive hormones.
- Pelvic ultrasound to examine the uterus and ovaries and look for fibroids, polyps, or features of PCOS.
- Endometrial sampling in some cases, especially with abnormal or postmenopausal bleeding, to check the uterine lining.
Keeping a record of cycle dates, flow, and symptoms is very helpful for diagnosis.
Treatment
Treatment is guided by the cause and your goals, such as cycle regulation or fertility.
- Lifestyle measures: Reaching a healthy weight, managing stress, and balancing exercise can regularize cycles when these are contributing.
- Hormonal therapy: Combined hormonal contraceptives or other hormone treatments to regulate periods.
- Treating underlying conditions: Such as thyroid disease, high prolactin, or PCOS.
- Treating uterine causes: Procedures or medication for fibroids or polyps when they affect bleeding.
- Fertility support for those trying to conceive when irregular ovulation is the issue.
Mild irregularity during adolescence or perimenopause often needs no treatment beyond reassurance and monitoring.
Prevention
- Maintain a healthy, stable weight
- Balance exercise with adequate nutrition and rest
- Manage stress and prioritize sleep
- Keep up with care for thyroid, hormonal, or uterine conditions
- Track your cycles so changes are noticed early
When to See a Doctor
See a doctor if you have:
- Periods that suddenly become irregular after being regular
- Cycles consistently shorter than 21 days or longer than 35 days
- Bleeding between periods or after sex
- Very heavy bleeding, or periods lasting longer than 7 days
- Any bleeding after menopause
Seek prompt care for very heavy bleeding with dizziness, weakness, or a racing heart, which can signal significant blood loss.
Frequently Asked Questions
What counts as an irregular period?
Periods are generally considered irregular when cycles are shorter than 21 days or longer than 35 days, when the timing varies a lot from month to month, or when flow and duration change markedly. Some variation is normal, especially in teens and during perimenopause.
What causes irregular periods?
Common causes include natural hormone shifts in adolescence and perimenopause, PCOS, thyroid problems, stress, significant weight change, intense exercise, certain medications, and uterine conditions like fibroids or polyps.
Are irregular periods a sign of a serious problem?
Often they are not, particularly in teens and around menopause. However, they can signal a treatable condition such as PCOS or thyroid disease, and certain patterns, like bleeding after menopause or very heavy bleeding, need evaluation.
Can irregular periods affect fertility?
They can, because irregular cycles sometimes mean ovulation is infrequent or unpredictable, which makes conceiving harder. Treating the underlying cause often helps, and fertility support is available for those trying to conceive.
When should I be worried about irregular bleeding?
See a doctor for bleeding between periods, after sex, or after menopause, for very heavy or prolonged bleeding, or for a sudden change in a previously regular pattern. Seek prompt care if heavy bleeding causes dizziness or weakness.
References
- Office on Women's Health, U.S. Department of Health and Human Services.
- American College of Obstetricians and Gynecologists (ACOG).
- Mayo Clinic. Menstrual cycle: What's normal, what's not.
- MedlinePlus, U.S. National Library of Medicine.