Progesterone Level Interpreter

It checks whether you ovulated on this cycle. After ovulation, the empty follicle becomes the corpus luteum, which pumps out progesterone during the second half of the cycle — the luteal phase — so a blood level drawn about a week after ovulation reflects that surge. The classic name is a "day-21" test because in a textbook 28-day cycle ovulation falls around day 14 and the draw is timed roughly 7 days later. The key word is timing: if your cycle is longer, shorter, or irregular, "day 21" may miss the peak entirely, and the number can look low simply because it was drawn on the wrong day. That's why the same lab value means very different things depending on when it was taken — the test is really about ovulation timing, and its result has to be read against your own cycle.

It's the reassuring direction. ACOG's guidance is that a progesterone value greater than about 3 ng/mL is evidence that ovulation occurred, so a mid-luteal result above that mark points to a cycle where you did ovulate. What it can't do is grade the quality of your luteal phase or promise a pregnancy. ACOG is explicit that because luteal progesterone can fluctuate several-fold over just a few hours, a single value should be used to confirm ovulation and not to assess how strong the luteal phase is. Some clinicians feel more reassured by higher mid-luteal values (a figure around 10 ng/mL is often cited), but that's a soft, assay-dependent marker, not a pass/fail line. So above 3 is a good sign about ovulation — read alongside your cycle history and your own lab's range, and confirmed by the clinician who ordered it.

Not necessarily, and this is the most misread result of all. A mid-luteal value under about 3 ng/mL doesn't provide evidence of ovulation on that test — but the single most common reason is timing, not a failure to ovulate. If the blood was drawn too early or too late relative to your actual ovulation, or if your cycle is longer or more irregular than the textbook 28 days, the level can read low even on a cycle where you ovulated normally. Progesterone also swings widely through the day. So a low reading is a reason to look closer — often by repeating the test with better timing (tracked against ovulation predictor kits or ultrasound) and talking it through with a clinician — not a diagnosis that you're not ovulating. If cycles are irregular or you've been trying for a while, that conversation is worth having sooner.

Because progesterone reference ranges are assay- and lab-specific, and because the number depends entirely on where you are in your cycle or pregnancy. Different labs run different tests that can report meaningfully different values from the same blood, and there's no single universal cut-off beyond the well-established "above ~3 ng/mL suggests ovulation" mark. On top of that, progesterone is released in pulses, so the level genuinely rises and falls through the day — a draw at 9am and one at noon can differ a lot. That's why this tool frames its bands as general context and keeps pointing you back to your own lab's reference range, which is printed on your report and is the authoritative one for you. If you're comparing results over time, using the same lab makes them more comparable.

On its own, no — and this is important. Progesterone does rise in early pregnancy, and very low or very high readings can be part of a clinical picture, but a single progesterone value is not a reliable test of whether a pregnancy is healthy or will continue. Early-pregnancy ranges are wide and overlap heavily between pregnancies that go on to be healthy and those that don't, so one number can't confirm or rule out a viable pregnancy. What clinicians actually use to assess an early pregnancy is the trend in beta-hCG (how the level changes over 48 hours) together with ultrasound once it's far enough along — see our hCG calculator for that side. That's why this tool treats early-pregnancy progesterone as general context only, never a viability verdict, and routes you to the clinician following your pregnancy. If you have bleeding, severe or one-sided pain, shoulder-tip pain, dizziness, or fainting, contact your clinician or seek urgent care straight away — regardless of any number.

Yes. This tool runs entirely in your browser: the value, unit, and context you enter are converted and interpreted on your own device and are never sent to a server, saved, or shared — close the tab and they're gone. We treat reproductive-health and pregnancy data as sensitive by default, so there's no account and nothing to delete. What you see is general educational information based on published guidance from ACOG, MedlinePlus, and ASRM's ReproductiveFacts; it isn't medical advice, a diagnosis, or a fertility or viability verdict, and it can't replace the clinician who ordered your test and your own lab's reference range.