Pradnya Ganorkar 
Quick answer: Medically, a cycle is irregular when it falls outside 24–38 days, varies by
more than about 7–9 days from cycle to cycle, or bleeding lasts beyond 8 days (FIGO definitions). Common causes include stress, significant weight change, over-exercise, PCOS
and thyroid disorders. One odd cycle is rarely a concern; a pattern over 2–3 cycles deserves
a doctor’s visit and a tracked record makes that visit far more productive.
First: what counts as “irregular”?
Most women who worry about irregular periods actually have normal variation. The medical
definitions (FIGO):
- Normal cycle: 24 to 38 days, counted from day 1 of one period to day 1 of the next
- Frequent: shorter than 24 days · Infrequent: longer than 38 days
- Irregular: cycle lengths varying by more than ~7–9 days month to month (threshold
- differs slightly by age)
- Prolonged bleeding: more than 8 days
So a cycle that is 29 days one month and 33 the next? Normal. 26 days then 47 days?
Worth attention.
The 7 most common causes
1. Stress — cortisol directly suppresses the hormones that time ovulation. Exam season,
job pressure, family stress: cycles respond.
2. Significant weight change — both rapid loss and gain disturb ovulation. Crash dieting
is a classic trigger.
3. Over-exercise + under-eating — training hard while eating too little can delay or stop
periods; it is a warning sign, not a fitness achievement.
4. PCOS — the most common hormonal disorder in Indian women of reproductive age;
national ICMR task force data found prevalence of 7.2%–19.6% depending on criteria
[2]. Irregular or infrequent periods are a core symptom.
5. Thyroid disorders — both hypo- and hyperthyroidism disturb cycles and are common and treatable.
6. Perimenopause — cycle variation naturally increases in the years before menopause.
7. New medication, recent illness, or stopping/starting contraception — usually
Temporary.
When to actually see a doctor
Book a visit if any of these hold:
- No period for 3+ months (and not pregnant)
- Cycles consistently shorter than 24 or longer than 38 days
- Bleeding beyond 8 days, or heavy flow with clots regularly
- Severe pain that disrupts daily life
- Irregularity plus acne/facial hair/weight gain (PCOS pattern) or fatigue/hair loss (thyroid pattern)
Take your tracked data with you. “My last four cycles were 44, 51, 39 and 48 days, heavy
flow days 1–2” turns a vague consultation into a targeted workup (typically thyroid profile,
hormone panel, possibly ultrasound).
FAQs
A: Variation up to about a week between cycles is normal for most adults. It is the pattern over months that matters, not one late period.
A: Yes, significant acute stress can delay ovulation, which pushes the whole cycle later.
A: No. They can make timing conception harder and sometimes indicate conditions (like PCOS) that affect fertility both are manageable with medical guidance.
A: Typically thyroid function (TSH), prolactin, and androgen levels, sometimes with a pelvic ultrasound. Your doctor decides based on your history which is where your tracked record helps.
References
1. FIGO definitions summarised in StatPearls: Physiology, Menstrual Cycle.
https://www.ncbi.nlm.nih.gov/books/NBK500020
2. Prevalence, Phenotypes, and Comorbidities of PCOS Among Indian Women (ICMR PCOS Task Force, JAMA Network Open 2024).
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC11581580
General wellness information, not medical advice. Consult a gynaecologist for diagnosis.