How Long After an LH Surge Do You Ovulate? (TTC Guide)

by Sep 11, 2021

If you are trying to conceive (TTC), you are probably already aware of the fact that you can only get pregnant during your fertile window. And within this fertile window, your chances of conceiving actually increase the closer you get to your ovulation day.

Tracking LH with Mira

Making sure to have sex with your partner on these “peak” fertility days is key to planning a successful pregnancy. However, it does require a bit of planning and taking the time to understand how your hormones work throughout the ovulation process.

To help, here is a closer look at the role of the luteinizing hormone (LH) in ovulation, how long after an LH surge you can expect to ovulate, and how Mira can help you to track your LH surge in order to more accurately predict ovulation.

How long after an LH surge do you ovulate?

For the majority of women who are considered healthy, ovulation typically occurs around 24 to 36 hours after the surge in luteinizing hormone (LH). Once ovulation is complete, LH levels then drop back to where they were prior to ovulation.

Typical baseline levels for LH range from 1.9 to 14.6 IU/L during the follicular phase and 0.7 to 12.9 IU/L during the luteal phase. However, during the LH surge and ovulation, LH can range from 12.2 IU/L all the way up to118.0 IU/L. For more information on LH levels and how they can vary, check out our recent article on LH levels here.

LH surge and ovulation

When does ovulation start after a positive ovulation test?

Ovulation tests measure the amount of luteinizing hormone (LH) present in your urine. If your ovulation test is positive, this indicates that your LH levels are high enough to be considered “surging”.

Once you receive a positive test, you can expect ovulation to take place within 24 to 36 hours. After ovulation, LH then decreases to its baseline.

It’s important to note that ovulation timings can vary among women. Some women ovulate as early as day 8 of their cycle, while others ovulate as late as day 21. Many women believe they ovulate on day 14, however, this is considered the average and is not necessarily what happens every month.

Finding the timing of your ovulation by simply logging your period on an app may not be enough to accurately determine your fertile window. Assuming you have a regular cycle, it could take more than one year of continuous logging to ensure that the calendar method becomes accurate for ovulation prediction.

However, LH testing alongside using the calendar method is a great way to more accurately and efficiently pinpoint your fertile window and day of ovulation.

How long am I fertile for after a positive ovulation test?

After you have received a positive ovulation test, you are considered fertile for the following two to three days. This should encompass the day before ovulation, the day of ovulation, and the day after ovulation.

Remember, sperm can live for up to five days within your body while an egg will only live for 12-24 hours after it is released through ovulation. Therefore, try to have sex with your partner as soon as possible after receiving a positive ovulation test as this is when your fertility is considered at its “peak”.

When should we have sex if we’re TTC?

If you are trying to conceive, you should be aware that you are only fertile for around six days during your cycle. This is called your “fertile window” and for the majority of women, it begins four to five days before ovulation and ends one day after ovulation.

Therefore, the best time to have sex with your partner if you are trying to conceive is:

  • In the three to four days leading up to ovulation
  • The day of ovulation and
  • The day after ovulation

Having sex with your partner anytime during this window should give you the very best chances of conceiving, with your highest chances being the day right before ovulation and the day of ovulation.

While it is not impossible to conceive outside of your fertile window, your chances of successful conception are low.

About the LH surge

The role of luteinizing hormone

LH is a reproductive hormone that triggers the start of your most fertile days. Normally, LH levels remain fairly steady throughout the menstrual cycle. The exception is just before ovulation when LH levels surge dramatically.

The time before ovulation is known as the follicular phase. During the follicular phase, follicles in the ovaries begin to mature, getting ready to release an egg. Eventually, one follicle emerges as the dominant follicle that will release its egg this menstrual cycle. The surge in LH triggers the release of the egg from the follicle, enabling ovulation.

When you ovulate, the egg released by the dominant follicle travels down the fallopian tubes. If it is fertilized within 24 hours, it will travel further down and implant in the uterus to begin growing into a baby. If not, the egg dies and is shed, along with the uterine lining, during your menstrual period.

Do you always ovulate after an LH surge?

A surge in luteinizing hormone only indicates that you are likely to ovulate soon. And even though an LH surge is a good sign that ovulation will happen, there is still a small chance that an egg may not be released. This could be due to a number of different health and lifestyle factors that can vary for each individual.

Because LH tests only predict when you are most likely to ovulate, you may want to supplement these tests with other testing and tracking methods for confirming ovulation. Here are three of the most common ways to do this.

  • Blood test at your doctor’s office. If a doctor is assisting you alongside your fertility journey, they may ask you to come in to take a blood test to confirm ovulation. Because heightened levels of progesterone are a sign of ovulation, this test will measure how much progesterone is present in your blood. Typically, this type of test can be taken around one week prior to when you are due for your next period.
  • Basal Body Temperature (BBT) Tracking. Another way to track and confirm ovulation is through basal body temperature (BBT) tracking. By taking your temperature each day at the same time, you may be able to identify a slight increase in temperature on the day that you ovulate. This method works best when used consistently over several cycles.
  • Pregnanediol Glucuronide (PdG) Testing. When your body produces progesterone after ovulation, this progesterone is eventually metabolized and released through your urine as pregnanediol glucuronide (PdG). This means that if your progesterone levels are elevated, your PdG levels will be elevated as well. However, instead of needing to go to your doctor’s office for a blood test, you can instead use an at-home PdG test to determine whether or not your PdG levels are higher than normal. PdG is likely to be at its highest around six to eight days after ovulation, so this would be the best time to plan for a test.

How long does the LH surge last?

On average, the entire LH surge lasts about two days. If you are trying to conceive, it’s important to pay attention to the length of your LH surge in relation to your ovulation day. This will allow you to plan sex with your partner on the days where you are at peak fertility.

LH isn’t the only hormone that surges ahead of ovulation. Before ovulation, estrogen also surges and initiates the start of your fertile window. Within the next three days, LH surges and triggers ovulation as well as marks the start of your peak fertile days. After ovulation, your egg can live for up to 24 hours but beyond that, the chance of conceiving is zero. This is why your fertile window ends 24 hours after ovulation.

Some people advise using the basal body temperature (BBT) method over tracking your LH surge for pinpointing ovulation. However, BBT does not rise until 12 to 24 hours after ovulation, so you may miss your fertile window if you are using the BBT method alone to track ovulation.

How to track your LH surge

When it comes to tracking your LH levels and pinpointing your LH surge, there are a few different methods that you can try. Here is an overview of the top three.

Blood test from a doctor’s office.

This is the most accurate method for tracking LH. However, it does require you to visit the lab for every test. For people trying to conceive (TTC) or trying to avoid (TTA) pregnancy, it usually requires 10-15 tests per month, which could be inconvenient and expensive. You can reduce the number of tests slightly, but it increases the chance of missing ovulation as you may not ovulate on the exact same day every cycle.

Given the expenses associated with frequent blood testing, this method is typically only recommended for those who are struggling to ovulate, finding it difficult to become pregnant, and/or those who are already undergoing fertility treatments with a doctor.

Testing at home with an ovulation predictor kit (OPK).

Another way that you can test and monitor your LH levels is with the help of ovulation predictor kits – also called “OPK’s”. These at-home test kits measure the concentration of LH in your urine, and they can give you insight into whether or not your LH levels are considered to be “surging”.

If your result is positive, this means that you are considered above the hormone threshold for LH set by the OPK manufacturer, which is usually based on the population average. A negative result means you are below the population average. However, due to the fact that everyone’s hormone levels can vary, a positive or negative result may not necessarily mean that your LH levels are elevated compared to your own personal baseline levels.

Additionally, for this method to work the best, you will also need to log your daily OPK results manually in a notebook or on your computer. While it’s not impossible to do, this extra step can be troublesome, stressful, and difficult to keep up with consistently.

Using a smart hormone tracker.

One of the best methods for tracking your LH levels is with an at-home smart hormone tracker like Mira. Together with the Mira app, you can see your actual LH concentrations with the accuracy of hospital-grade lab equipment. Mira works similar to an at-home pregnancy test, and it can measure your LH, estrogen, and other female hormone concentrations in your urine. This data is then automatically synced with the Mira app, which optimizes the ovulation prediction based on your personal health. It is accurate, easy to use, and adapts to your individual hormone patterns.

How Mira can help you track your LH surge

Mira empowers you to measure, monitor, and track hormone concentration levels in your body – specifically the fertility hormones LH and E3G. To do this, you need to have the Mira Analyzer, several Mira Fertility testing wands, and the Mira app downloaded onto your phone or tablet.

To begin tracking for your LH surge specifically, all you need to do is start testing!

Simply collect a urine sample in one of the provided cups, dip your test wand into the sample and leave it there for 10-12 seconds, and then insert the test wand directly into the Mira analyzer. The analyzer will provide you with a numeric value of your body’s exact levels of LH and E3G. This information will then be recorded and synced with the Mira app, allowing you to track your LH levels over the duration of your cycle.

Once you’ve taken several tests, you should be able to identify a spike in your levels of LH. For most women, this surge in LH is a sign that ovulation should occur within the next 24-36 hours. Together with your partner, you can use this information to plan intercourse on the days that you are the most fertile.

For the majority of women, testing every day starting no later than the 6th day of your cycle should be sufficient for accurately predicting your LH surge. Testing daily may also be advantageous for beginners wanting to know more about their fertility cycle and those struggling with hormonal conditions such as PCOS.

If you would like to learn more about how testing with Mira works, check out this article: A Complete Guide to Testing with Mira Fertility Plus.

✔️ Medically Reviewed by Katerina Shkodzik, M.D., OB-GYN

Dr. Katerina Shkodzik is a certified OB-GYN with a special focus on reproductive endocrinology and infertility issues. She has been practising since 2015.

Dr. Shkodzik completed her residency program in the Department of OB/GYN at the Belarusian State Medical University and fellowship program in the Department of Gynecological Surgery at the Medical University of Bialystok, Poland.

Dr. Shkodzik is extensively involved in digital health projects providing her medical expertise and integrating of cutting edge technologies in medical science and clinical practice since 2018.

Dr. Shkodzik has participated in several studies focused on PCOS, endometriosis, menstrual cycle characteristics and their abnormalities based on big data of digital health in collaboration with leading universities.

She believes that paying special attention to women's health is a crucial step to improving the world we live in.

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