| "Helping women track their ovulation in a smarter way" | 
If you’ve seen ads for ovulation tests that check estrogen instead of just LH (luteinizing hormone), you might be wondering if your usual LH-based ovulation test is missing something. Most ovulation predictor kits (OPKs), like Premom paired with easy@Home strips, detect the LH surge. A new study suggests you probably aren’t missing much by skipping estrogen.
Researchers at Queen’s University recently compared two ways of scheduling a fertility test visit: one based on a rising estrogen signal, the other based on the classic LH surge. The estrogen-based approach didn’t get women any closer to their actual ovulation day than the LH-based one did.
Short version: if you’re already testing LH with an ovulation predictor kit (OPK), like Premom paired with easy@Home ovulation strips, this research doesn’t suggest you’re missing a step by skipping estrogen testing.
Key takeaways
- A small 2025 study found that scheduling a test visit off an early estrogen rise didn’t get women closer to ovulation than scheduling it off the standard LH surge.
- Researchers followed 21 naturally cycling women, split into two groups: one used an estrogen-based test, the other used a standard LH test, to time a follow-up visit.
- Both groups landed about the same distance from ovulation, roughly two and a half days on average, no matter which test they used.
- If you’re tracking with an LH-based ovulation predictor kit, this research doesn’t suggest you need to add estrogen testing on top of it.
What the study did
Some digital ovulation tests look for the estrogen rise that comes before the LH surge; a standard ovulation test reads the LH surge itself.
Researchers recruited 21 naturally cycling women, in their early twenties on average, for a study on menstrual cycle testing methods. Each woman had two visits: one early in her cycle, and one later, timed by whichever test she’d been assigned.
Ten women had their later visit scheduled off a rise in estrogen, ahead of the LH surge (call it the „advanced” test). Eleven women had theirs scheduled off the LH surge itself, the same signal most standard OPKs read (the „standard” test). The study, led by Lindsay Lew and Kyra Pyke, was published in Physiological Reports in April 2025.
Does tracking estrogen predict ovulation better than LH?
Not really, based on this study. Women in the estrogen-test group landed 2.7 days from ovulation on average. Women in the standard LH-test group landed 2.5 days from ovulation on average. That gap wasn’t statistically meaningful.
Estrogen did rise ahead of the LH surge in both groups, which is expected biology. But catching that earlier rise didn’t translate into better timing in practice, at least not in this sample.
How did the estrogen and LH tests compare?
Here’s how the two groups compared, in the researchers' own numbers:
| Outcome | What the researchers found | Evidence quality |
| Days from test visit to ovulation | Estrogen-based test: 2.7 days on average. LH-based test: 2.5 days on average. No meaningful difference (p = 0.859). | Preliminary, small study |
| Estrogen rise before the LH surge | Estrogen rose ahead of the LH surge in both groups, as expected, but this didn’t translate into better scheduling in practice. | Preliminary, small study |
This was a small, preliminary study of 21 healthy cycling women, not a clinical trial in women trying to conceive, so it’s worth treating as an early signal rather than a final word.
Why does the LH surge still matter for timing ovulation?
The LH surge is what actually triggers the egg’s release, usually about 24 to 36 hours later. Estrogen climbs earlier in the cycle and can hint that a surge is coming, but it doesn’t mark the moment the way the LH surge itself does. That’s likely why testing for LH, on its own, still lands you close to the fertile window.
Should you add an estrogen test to your routine?
If you’re using Premom with easy@Home ovulation test strips, you’re already reading the LH surge daily around your fertile window. Premom reads each easy@Home strip and turns it into a point in your cycle trend, so a single line becomes a pattern. Based on this research, that’s the signal doing the real work of timing.
If you want reassurance that ovulation likely happened, that’s a separate question from timing it, and it’s what a PdG test is for. Testing LH tells you a surge is likely coming; a PdG test a few days later can help reassure ovulation likely followed.
What this study doesn’t tell us
This was a small study, just 21 women, and it split them into two separate groups rather than having the same women try both tests. The participants were healthy, naturally cycling volunteers in a research study, not necessarily women actively trying to conceive. Larger studies in a TTC population would help confirm whether this holds up broadly.
Keep testing, keep logging.
