You may have heard that the levels of LH are tight to ovulation. LH is the luteinizing hormone, one of the most important hormones that regulate our cycles and fertility. The LH surge causes the release of an egg into the fallopian tube. This process is ovulation. Ovulation often happens 24 to 36 hours after the LH surge. You have the best chances of getting pregnant during this time.
When does ovulation actually happen?
Ovulation time varies. When trying to understand when your fertile and infertile days are, it’s important to understand how long after the LH surge you ovulate.
Ovulation happens when an egg is released from an ovary. For healthy women, it usually happens once every menstrual cycle. The length of a menstrual cycle varies from cycle to cycle and woman to woman. It usually ranges from 21 to 35 days.
Ovulation time varies as well. Women can ovulate as early as day 8 of their cycle, or as late as day 21. Many women believe they ovulate on cycle day 14, but this is considered the average, not necessarily what happens every month.
Simply logging your period on an app may not be enough to accurately determine your ovulation. It often takes more than one year of continuous logging to ensure the calendar method is accurate enough to predict ovulation.
What do Estrogen and LH surges mean in relation to ovulation?
A few days after the period, your body starts to produce a hormone called estrogen. Estrogen helps to increase the thickness of the uterus wall and creates a mucus environment that is sperm-friendly.
Healthy sperm can live up to 5 days within women’s cervical mucus. Estrogen usually starts to increase about 4-5 days before ovulation. Estrogen is considered as a good predictor of the fertile window.
You become more fertile when you get closer to ovulation day. High estrogen level triggers a sharp increase in the luteinizing hormone. This is considered the “LH surge”. The LH surge triggers the release of a mature egg into the fallopian tube, which is what we know as “ovulation”. All in all, estrogen surge causes the LH surge, which in turn leads to ovulation.
The LH surge is a rather sharp change of the hormone and lasts very briefly. Given that inter-woman and inter-cycle hormone variabilities are huge, it’s common to miss the LH peak when testing using OPK’s.
According to a study, the LH peak value could be as low as 20 IU/L, or as high as 75 IU/L. Ovulation predictor kits or OPK’s uses a fixed hormone threshold to determine + or – in an ovulation test. Some of them show a “smiley face” vs. “no smiley face”. Without adjustment towards personal variability, missed peak or prolonged “high” is likely to happen.
24-36 hours after the LH surge, ovulation usually happens. LH is a good indicator of ovulation and your peak fertility days. It then decreases sharply. The entire LH surge lasts about 2 days.
The Egg lives up to 24 hours after ovulation. Beyond 24 hours, the chance of conceiving is zero. Your fertile window starts from the day of Estrogen surge, reaches peak fertility at LH surge, and ends at 24 hours after ovulation. Body temperature rises 12 hours after ovulation, so it identifies the last 12 hours of the fertile window instead of capturing the entire 6 days of the fertile window.
What are the best ways to test for Estrogen and LH Levels in order to predict ovulation?
There are multiple ways to test for Estrogen and LH, including:
- A blood test from a doctor – This is the most accurate way. However, it requires you to visit the lab for every test. For people trying to conceive (TTC) or trying to avoid pregnancy (TTA), it usually requires 10-15 tests per month. This can be troublesome. You can reduce the number of tests slightly, but it increases the chance of missing the ovulation. You may not ovulate on the exact same day every cycle.
- Testing at home with an OPK – A positive result means you are above the average hormone level and are considered as “ovulating”, and a negative result means you are below. However, a positive or negative result may not necessarily mean you ovulate or not, due to the huge inter-woman hormone level variabilities. You would also need to log down the daily OPK results manually, which could be troublesome and stressful.
- Smart hormone tracker – Mira fertility tracker is a palm-sized hormone tracker that tracks and shows you your actual hormone concentration. It is intended for home use, but it has the accuracy of hospital-grade lab equipment. Mira measures your LH, Estrogen, and other female hormone concentrations in urine. The data is automatically synced with the Mira App, which optimizes the ovulation prediction based on your personal health. It is accurate, easy to use, and smart.
When to test Estrogen and LH levels?
If you are trying to conceive (TTC) or trying to avoid (TTA), it is best to start early during a cycle. As cycle length and ovulation date could vary, starting early can reduce the risk of missing fertile days.
However, testing more frequently is associated with higher costs. Mira’s artificial intelligence learns your cycle and tells you when to test only when it is needed. Mira helps you to avoid missed fertile days while not wasting any tests.
Takeaway
- Ovulation timing varies! A woman could ovulate on as early as day 8 of her cycle, or as late as day 21.
- Estrogen and LH surges are the triggers and causes of ovulation. Testing Estrogen and LH levels are the most accurate home-use ways to detect ovulation.
- Your fertile window starts from the day of Estrogen surge, reaches peak fertility at LH surge, and ends at 24 hours after ovulation. 24-36 hours after LH surge, ovulation usually happens.
- Since hormone levels differ from woman to woman and cycle to cycle, you may want to choose an accurate and personalized way to test them. It should also be easy to use for the long term.
