Oligomenorrhea
A menstrual cycle lasting 36 to 38 days is called oligomenorrhea, which is defined as cycles longer than 35 days. 1
Definition and Normal Parameters
- Normal menstrual cycle length ranges from 21 to 35 days in adult women, with cycles occurring regularly within this interval defined as eumenorrhea 1
- Oligomenorrhea specifically refers to cycles exceeding 35 days, making your 36-38 day cycles fall into this abnormal category 1
- Research confirms that only 0.9% of regularly menstruating women have usual cycle lengths greater than 35 days, indicating this is outside the normal range 2
Clinical Significance
This is not a normal variant and warrants medical evaluation. 3 While there may be a tendency to dismiss irregular cycles as normal, cycles greater than 35 days apart are definitively abnormal and require assessment 3. The 95th percentile for time interval between cycles is 90 days, meaning amenorrhea (absence of periods) for greater than 3 months is clearly pathological 4.
What Requires Evaluation
Your cycles at 36-38 days indicate:
- Potential underlying hormonal dysfunction affecting the hypothalamic-pituitary-ovarian axis 4
- Possible conditions including polycystic ovary syndrome (PCOS), which affects 4-6% of women and commonly causes irregular periods 3
- Thyroid disorders (both hyperthyroidism and hypothyroidism) can cause menstrual irregularities 3
- Hyperprolactinemia should also be ruled out 3
Recommended Evaluation
Initial workup should include: 3
- Pregnancy test (most common cause of menstrual irregularity)
- FSH and estradiol levels
- Prolactin level
- TSH (thyroid function)
- Mid-luteal progesterone
History should assess: 3
- Contraceptive use and medication history
- Weight changes and exercise patterns
- Stress factors
Critical Pitfall to Avoid
Do not delay evaluation beyond 4 months of irregular cycles – this represents secondary amenorrhea and requires referral 3. Never assume irregular bleeding is "normal" simply because you're menstruating; the interval matters significantly for long-term health, particularly bone health 4.