What Hormone Testing Can (and Can’t) Tell You
I’ll start with a spoiler: there is no single perfect way to test most hormones.
Many of my clients, whether they're navigating infertility, intense PMS, or perimenopause, understandably want to know what the heck is going on with their hormones. Hormone testing is one of the places I most often see people get stuck, but imperfect doesn't mean pointless. Throwing our hands up and skipping testing altogether isn't the answer (many of my clients have heard that advice before). Instead, I think the goal is to gather relevant data, look at how it lines up with your symptoms, and stay honest about what that data can and can't tell us.
It's easy to assume a lab result is the final word on your hormones. In reality, most blood work, not just hormone testing, shows us a snapshot of one moment in time. For some hormones, that's perfectly fine. For others, it's a real limitation.
Estradiol: the right test for some question
Serum estradiol is typically tested on day 3 of your cycle (the third day of your period). This gives us helpful information about ovarian function, and it's a critical time to test if you're moving forward with assisted fertility options like IUI or IVF. Still, that's far from the only reason you might want to look at your hormones. If you're dealing with PMS or heavy periods, a day 3 estradiol level tells us very little, because those symptoms are driven by what's happening at other points in your cycle.
Progesterone: a moving target
Progesterone has an even bigger limitation with serum testing. Ideally, we test it about midway between ovulation and your next period, when levels peak roughly 6 to 8 days after ovulation (Practice Committee of the American Society for Reproductive Medicine, 2021). For someone with a 28-day cycle who ovulates on day 14, that means testing around day 21.
Here's the catch: even when the timing is right, a single blood draw doesn't capture progesterone production very well. After ovulation, the corpus luteum makes progesterone and releases it in pulses throughout the day. A blood draw taken right after a pulse might look high, while one taken between pulses might look low.
How big a difference are we talking? Progesterone levels can swing up to eight-fold within just 90 minutes. So if you're trying to understand progesterone production for fertility, one serum result can vary a lot depending on exactly when your blood was drawn.
A combination approach
So if blood work isn't perfect, what else is there? Serum testing is still the standard for estradiol and progesterone, but I find that pairing it with urine-based tracking gives us the clearest picture. Urine testing measures metabolites of estrogen and progesterone, which gives us an indirect, day-by-day look at how these hormones rise and fall across your entire cycle.
There are a few at-home devices that track these metabolites in real time, and my favorite is the Mira Fertility Tracker. This method isn't perfect either, especially when it comes to exact hormone levels. That's why interpreting the results in the context of your symptoms matters so much. When I look at patterns across your cycle alongside what you're actually experiencing, I get a much clearer sense of what kind of support will help you most.
A few things can make your testing far more useful:
Start with your question. Are you looking at ovarian function, ovulation, PMS, or perimenopause? The question decides which test fits and when to take it.
Time it to your cycle, not the calendar. "Day 21" only works for a 28-day cycle. If your cycles are longer or shorter, aim for about a week after ovulation instead.
Track your cycle before you test. Knowing your cycle length and roughly when you ovulate makes it much easier to time blood work well.
Look for patterns, not single numbers. Tracking across a full cycle, or a few, tells us far more than any one data point.
Bring your symptoms into the conversation. Lab results mean the most when they're read alongside how you actually feel.
Hormones are complicated, period (pun totally intended). Testing them is no exception, but that doesn't mean you can't get answers and, most importantly, solutions. Blood work is always a good place to start. Hormones I regularly check through serum testing include thyroid markers, DHEA, testosterone, FSH, LH, and prolactin. Timing still matters for some of these, but serum testing remains the most validated and accurate way to measure the hormones circulating in your body. If your main concerns are related to your cycle, serum testing paired with real-time tracking will usually give us the most complete picture.
Having this data is useful, but knowing what to do with it is what actually helps you feel better. Your results aren't a verdict. They're a starting point for building support that fits your body and your life.
References:
Filicori, M., Butler, J. P., & Crowley, W. F., Jr. (1984). Neuroendocrine regulation of the corpus luteum in the human: Evidence for pulsatile progesterone secretion. Journal of Clinical Investigation, 73(6), 1638–1647. https://doi.org/10.1172/JCI111370
Practice Committee of the American Society for Reproductive Medicine. (2021). Diagnosis and treatment of luteal phase deficiency: A committee opinion. Fertility and Sterility, 115(6), 1416–1423. https://doi.org/10.1016/j.fertnstert.2021.02.010