01/07/2026
Cycle Day 1: it sounds simple, but it’s one of the most confusing parts of fertility care.
What is Cycle Day 1?
Cycle Day 1 is the first day of full menstrual flow. This does not include spotting or light brown discharge. It means a true bleed that requires a pad or tampon.
Why is it confusing?
Many people spot for days before their period truly begins. Hormonal shifts, progesterone withdrawal, or even an early pregnancy loss can blur the lines. This is why “Is this Day 1?” is one of the most common questions I hear.
How to tell if it’s truly Day 1
• Bright red flow
• Needing menstrual protection
• Flow that continues or becomes heavier the next day
If you are unsure, it is always okay to ask. Clinics expect this question.
Why Cycle Day 1 matters for fertility treatment
Cycle Day 1 sets the timing for many important steps, including baseline ultrasounds and bloodwork, starting fertility medications, timing ovulation induction, IUI, or IVF, and coordinating treatment safely and accurately.
Bottom line
Cycle Day 1 is not just a date on the calendar. It is a key starting point for understanding your hormones and planning fertility treatment. When in doubt, ask. You are not doing it wrong.