How Long After LH Surge Do You Ovulate?

By OBGYN Dr. Kenosha Gleaton

Trying to conceive (TTC) is all about timing- having sex around the right time of the month when you can give sperm and egg the best chance of meeting. This requires timing sex around ovulation, which is only a short period of time that occurs about once a month. Tracking and timing ovulation can be done using a few different tools, including cervical mucus tracking, ovulation calculators, and more. [1] Research shows that the most accurate way to predict ovulation is by using an ovulation test kit that measures luteinizing hormone (LH). [2] 

What Is LH?

Luteinizing hormone (LH) is one of the key reproductive hormones that play an important role in the menstrual cycle and ovulation. In people assigned female at birth, LH is the hormone that tells the body when to release a mature egg (ovulation). In people assigned male at birth, LH tells the body to produce testosterone. 

Why Should I Track My LH Levels?

In people AFAB, tracking LH levels can give them a good idea of where they are in their menstrual cycle. At the beginning of a menstrual cycle, such as day 1 of your period, most reproductive hormones, including LH, are relatively low. [1-2] Nearing ovulation, progesterone, LH, and FSH all begin to rise. LH reaches its highest point, aka its peak, at the time of ovulation. This is when the body will release a mature egg. [1-2] If someone is hoping to time sex around ovulation, tracking LH levels can be very helpful. Keep reading about LH levels throughout the menstrual cycle → 

How Long After an LH Surge Do You Ovulate?

Research shows that ovulation occurs about 8-20 hours after an LH surge, or about 28-36 hours after LH begins to rise. [3] It’s difficult to determine exactly when the ovary will release an egg without close monitoring, but ovulation tests are a great tool for identifying the days leading up to and including ovulation.  

Can You Ovulate On the Same Day as LH Surge?

Yes, you will likely ovulate the same day as your LH surge. Studies show that ovulation typically occurs within 20 hours after LH levels peak. [3] So if you’re hoping to conceive, it’s recommended to have unprotected sex in the days leading up to and the day of ovulation if you’re hoping to optimize your chances. Learn what to do if you aren’t ovulating >>

How to Test Your LH Levels

There are a few ways to measure your LH levels or track ovulation, from lab tests to at-home urine tests. 

Blood Sample

Using a blood sample, a healthcare provider can measure many different parameters and hormones, including LH, FSH, estrogen, and more. [4] Blood samples can produce results within a few days, which may not be ideal if you’re hoping to gain insight into your levels immediately. Blood tests can help you understand your baseline hormone levels or confirm if you are ovulating at all. You can even test key hormones with at-home lab tests like the women’s fertility test. 

Urine Sample

The most convenient and timely way to test LH levels from home is by using an ovulation test kit or ovulation predictor kit. [2,4] These are similar to pregnancy tests and work by measuring the amount of LH in your urine. When the concentration of LH is high enough, the test will give a positive result, letting you know that you are likely to ovulate in the next few hours. 

Other symptoms of ovulation you may want to note include changes in cervical mucus, basal body temperature, cramping, mood changes, appetite changes, and more. [1-3] 

Natalist's Role in Your Pregnancy Journey

The menstrual cycle is a complex process that is marked by changing hormone levels. Whether you’re tracking ovulation in hopes of trying to conceive, prevent pregnancy, or you’re just interested in your cycle, it can be very helpful and empowering to get a better understanding of your body. Natalist is here to support your reproductive journey in every phase. Support cycle regularity and reproductive health with menstrual cycle supplements and prenatal vitamins for women, or support pregnancy and postpartum health with postnatal vitamins, self-care products, and more. 

References:

1. Yu JL, Su YF, Zhang C, et al. Tracking of menstrual cycles and prediction of the fertile window via measurements of basal body temperature and heart rate as well as machine-learning algorithms. Reprod Biol Endocrinol. 2022;20(1):118. Published 2022 Aug 13. doi:10.1186/s12958-022-00993-4
2. Su HW, Yi YC, Wei TY, Chang TC, Cheng CM. Detection of ovulation, a review of currently available methods. Bioeng Transl Med. 2017;2(3):238-246. Published 2017 May 16. doi:10.1002/btm2.10058
3. Kerin J. Ovulation detection in the human. Clin Reprod Fertil. 1982;1(1):27-54.
4. Luteinizing Hormone (LH) Levels Test. Medline Plus. National Library of Medicine. Accessed January 2024. https://medlineplus.gov/lab-tests/luteinizing-hormone-lh-levels-test/

Dr. Kenosha Gleaton is board-certified in gynecology and obstetrics and is the Medical Advisor of Natalist. She received her MD from MUSC and completed her residency at Carolinas Medical Center in Charlotte, NC.

Dr. Gleaton is passionate about women, health equity, and mentoring. She is the CEO of The EpiCentre, an OBGYN spa-like practice, and is a Clinical faculty member of Charleston Southern University. She is also a member of the American College of Obstetrics & Gynecology, the American Association of Gynecologic Laparoscopists, and the American Association of Professional Women.