Measuring Ovulation with FSH, LH, and Progesterone
To accurately measure ovulation, progesterone levels during the mid-luteal phase (approximately 7 days after suspected ovulation) provide the most reliable hormonal indicator, with levels ≥5 ng/ml confirming ovulation has occurred.
Hormonal Patterns During Normal Ovulatory Cycle
Follicular Phase (Early Cycle) Assessment
- Baseline FSH and LH measurements should be taken between days 3-6 of the menstrual cycle, with accurate assessment calculated as the average of three estimations taken 20 minutes apart 1, 2
- During early follicular phase, FSH levels are typically higher than LH levels 3
- Normal LH/FSH ratio should be less than 2; a ratio >2 suggests PCOS and likely anovulation 1, 2
Mid-Cycle (Ovulation) Assessment
- LH surge occurs approximately 24-36 hours before ovulation 2
- Both LH and FSH peak at mid-cycle, with LH showing a more dramatic increase 3, 4
- Urinary LH testing can predict ovulation within 48 hours with 92% positive predictive value 5
Luteal Phase Assessment
- Progesterone measurement during mid-luteal phase (approximately 7 days after suspected ovulation or day 21 of a 28-day cycle) is the most reliable hormonal indicator of ovulation 6, 2
- A serum progesterone level ≥5 ng/ml (≥16 nmol/L) on day 21 confirms ovulation has occurred 6
- Progesterone levels during luteal phase should be 10-15 times higher than during follicular phase (typically 12.4 ± 2.3 ng/ml in luteal phase vs. 0.65 ± 0.12 ng/ml in follicular phase) 3
- Low mid-luteal phase progesterone levels (<6 nmol/L) indicate anovulation 1, 2
Practical Approach to Measuring Ovulation
Timing of Hormone Measurements
- For FSH/LH baseline: Measure on days 3-6 of menstrual cycle 1, 2
- For progesterone: Measure on day 21 of a 28-day cycle (or 7 days before expected menses in irregular cycles) 6
- For women with irregular cycles, testing should be performed approximately 7 days before expected menses to capture mid-luteal phase 6
Interpreting Results
- Normal ovulatory pattern shows:
Abnormal Patterns Suggesting Anovulation
- LH:FSH ratio >2 suggests PCOS 1, 2
- FSH >35 IU/L and LH >11 IU/L suggest ovarian failure 1, 2
- LH <7 IU/mL may indicate hypothalamic dysfunction 1, 2
- Progesterone <5 ng/ml during mid-luteal phase suggests anovulation, mistimed sample, or luteal phase defect 6
Common Pitfalls and Considerations
- Timing of sample collection is critical - measurements must be taken at specific points in the cycle 2
- The "day 21" progesterone timing is based on a 28-day cycle; adjustment needed for women with irregular cycles 6
- Medications, particularly hormonal contraceptives, can suppress normal hormone patterns and affect results 6, 2
- Some conditions like PCOS can show elevated LH levels throughout the cycle, masking the typical surge pattern 2
- A single hormone measurement may be insufficient; serial measurements provide more reliable information 7
Alternative Assessment Methods
- Urinary LH testing (surge precedes ovulation by 24-36 hours) can be used as a home-based alternative method 6, 5
- Transvaginal ultrasound to monitor follicular development and collapse is the most direct method to confirm ovulation 7, 5
- Combined approaches using both hormone measurements and ultrasound provide the most comprehensive assessment 7, 5