Let’s talk about that thing no one really brings up—those few days of spotting before your period. It might seem normal (or even harmless), but if you’ve been trying to conceive and feel like you’re “doing everything right,” that little bit of bleeding could actually be your body trying to get your attention.

In the fertility world, spotting before your period can sometimes point to low progesterone or what’s called a luteal phase defect—a fancy way of saying the second half of your cycle (after ovulation) may not be long or strong enough to support implantation.

Here’s why it matters:

• Progesterone’s job is to thicken the uterine lining and keep it stable so an embryo can implant and stay put.
• If levels drop too soon, the lining can start to break down—hello spotting—and the window for implantation might close too early.
• It’s also something that can easily be missed in standard fertility workups unless you’re looking at the right labs at the right time (timing really is everything here).

If you’ve ever wondered:

• “Why do I spot for days before my period actually starts?”
• “Is my cycle too short to support pregnancy?”
• “How do I know if my progesterone is low?”

You’re not alone—and there are ways to check and support this naturally.

In our work, we’ve seen so many women finally get answers—and pregnancies—when they started paying attention to this one small but mighty clue.

How to actually test for low progesterone

This is where things get tricky. Many women are told their hormone levels are “normal” because they were tested on cycle day 3—which is perfect for checking FSH and estradiol, but way too early for checking progesterone.

You need to test progesterone during your luteal phase—ideally 5–7 days after ovulation.
For a 28-day cycle, that’s usually around day 19–21. But if you ovulate late, you’ll need to test later too. Timing matters more than the day of your cycle.

Look for:

• Serum progesterone levels above 10 ng/mL (ideally 15–25 for fertility)
• Some providers also recommend tracking it with a urine metabolite like pregnanediol glucuronide (PdG) using at-home strips

If your levels come back low—or your luteal phase is consistently under 10 days—it’s worth supporting.

Want to learn more about progesterone? Check out my progesterone guide here.

​reminder: i’m currently accepting people into my Nurture Your Fertility program. you can learn more here about the program and fill out an application!