On cycle day 9 with an estrone‑3‑glucuronide (E1G) level of 8.5 after a 4.5‑hour sample hold and only 2 hours of sleep, am I currently in the fertile window?

E1G Level of 8.5 on Cycle Day 9: Fertile Window Assessment

You are likely approaching but not yet in your fertile window, as an E1G of 8.5 on cycle day 9 represents a low-to-baseline level that has not yet shown the sustained rise needed to signal impending ovulation.

Understanding Your E1G Reading

Your E1G level of 8.5 needs to be interpreted in the context of your baseline values and the pattern of rise, not as an absolute threshold 1, 2.

Key Interpretation Points:

• Baseline E1G levels in the early follicular phase typically range from low single digits to mid-teens, with significant individual variation 2, 3
• A sustained rise in E1G (typically 50% above the mean of the three preceding values) is the most reliable indicator that the fertile window is beginning 2, 4
• The fertile window typically begins 2-6 days before ovulation, with an average of 5.3 fertile days detected from E1G rise to PdG rise 1

Your Specific Situation:

• At cycle day 9 with E1G of 8.5, you are in the mid-follicular phase where E1G should still be relatively low 3
• The suboptimal sample conditions (4.5-hour hold instead of first morning urine after full night's sleep, only 2 hours of sleep) may have diluted your sample, potentially underestimating your true E1G level 2, 3
• Day-to-day variation can be significant (coefficient of variation ~25-40%), which is why tracking the pattern over consecutive days is more informative than a single value 2

What to Do Next

Immediate Actions:

• Continue daily E1G monitoring with proper first morning urine collection (after at least 4-6 hours of sleep without voiding) to establish your baseline and detect the sustained rise 2, 3
• Look for a sustained rise of approximately 50% above your mean baseline values over 2-3 consecutive days, which typically occurs 3-7 days before the LH surge 2, 4
• Peak E1G levels are typically 5-7 fold higher than baseline, so you should expect values rising into the 40s-60s range as you approach ovulation 2

Timing Expectations:

• If you have a typical 28-day cycle, ovulation usually occurs around cycle day 14, meaning your fertile window would begin around cycle days 9-12 1, 3
• The E1G rise typically precedes the LH surge by 2-3 days, and the LH surge itself occurs 1-2 days before ovulation 1, 4
• Given you're on cycle day 9 with a low E1G, you likely have 1-4 days before entering the fertile window, but this requires confirmation with continued monitoring 3, 4

Critical Caveats

Sample Collection Issues:

• Inadequate sleep and short urine hold times can significantly affect hormone concentration measurements, leading to falsely low readings 2, 3
• First morning urine after a full night's sleep (6-8 hours) provides the most reliable and concentrated sample for accurate E1G measurement 2, 3
• Your current reading may underestimate your actual E1G level due to dilution from the short hold time 2

Individual Variation:

• Normal menstrual cycles show significant variability in hormone patterns, with 40% of cycles showing more complex profiles than textbook descriptions 3
• Some women have multiple E1G peaks representing growth and atresia of different follicles before the final ovulatory follicle emerges 3
• The ratio of E1G to creatinine can reduce day-to-day variation and improve accuracy, though you haven't mentioned measuring creatinine 2

Fertility Window Determination:

• Do not rely on a single E1G value to determine fertility status; the pattern of sustained rise over multiple days is what matters 2, 4
• If trying to avoid pregnancy, assume fertility begins when E1G shows a sustained rise and continues until at least 3 days after the LH surge or when PdG shows sustained elevation 1, 4
• If trying to conceive, the most fertile days are the 2-3 days before ovulation, which correspond to peak E1G levels just before the LH surge 1, 4