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Understanding the LH Surge: Your Key to Optimizing Fertility

06.13.2023 / The Oova Team
Understanding the LH Surge: Your Key to Optimizing Fertility

Are you trying to conceive and having trouble finding your fertile window? Understanding the LH surge, the pivotal event in the reproductive journey, can be the missing piece of the puzzle on your path to parenthood. 

The LH surge, or luteinizing hormone surge, signals the prime window of fertility and ovulation. If you can detect or predict the LH surge, you can know when to time intercourse and increase your chances of conception. Whether you're just embarking on your fertility journey or have been diligently trying for a while, here’s everything you need to know about the LH surge and how to take control of your fertility like never before.

What it is     LH surge and fertility     How to detect LH surge     LH surge range     

What is the LH surge?

The LH surge is an important moment in your menstrual cycle that's all about fertility. LH, short for luteinizing hormone, is produced by the pituitary gland—a tiny but mighty gland at the base of your brain. It's like the conductor of an orchestra, calling the shots for your reproductive system, and the LH surge is like the big finale.

When your pituitary gland releases a surge of LH into your bloodstream, it signals to your ovaries to get ready for ovulation. As LH levels skyrocket, it triggers the bursting of the ovarian follicle, releasing that precious egg. 

This is the optimal time for fertilization because once that egg meets sperm, it's on its way to potential implantation. So, knowing when the LH surge happens gives you the power to make informed choices and boost your chances of conception.

LH surge and fertility

The LH surge and fertility are correlated because the LH surge triggers ovulation—and ovulation is the key to figuring out your fertile window. Once you know your fertile window, you and your partner can time your intercourse optimally and increase your chances of conception.

The LH surge is also a great measure of fertility because it can help people who have irregular cycles. Instead of estimating when you’re ovulating based on the day of your cycle, the LH surge provides a clear picture so you never have to guess.


Finally, the LH surge can help you monitor your hormone health, which can affect your fertility.  The presence and timing of the LH surge provide insights into the overall health of the reproductive system. Consistent and predictable LH surges are indicators of a healthy ovulation process. On the other hand, irregular or absent LH surges may signify underlying hormonal imbalances that can affect fertility. Tracking the LH surge can help identify potential issues and prompt individuals to seek medical advice if needed.

>>RELATED: 8 Signs Your Hormones May Be Out of Balance – And What to Do Next.

Understanding the significance of the LH surge empowers people who are trying to conceive to take an active role in optimizing their fertility. By tracking and interpreting the LH surge, couples can make informed decisions and increase their chances of achieving their desired goal of pregnancy.

How long after an LH surge are you fertile?

Generally, after the LH surge, ovulation typically takes place within the next 24 to 36 hours. This means that the window of optimal fertility typically extends for about two to three days after the surge.

It's worth noting that every menstrual cycle can vary, and the length of the fertile window may also differ. Factors such as hormone levels, overall health, and individual variations can influence the precise timing. Therefore, it's advisable to track your menstrual cycle, monitor LH surges consistently, and consult with a healthcare professional for personalized guidance.

When to have sex after the LH surge

If you’re trying to conceive, you’ll need to have sex during this window so the sperm can fertilize the egg that was released during ovulation. Keep in mind that sperm can survive inside the female body for up to five days, so having intercourse in the days leading up to and after the LH surge can extend your fertile window and increase your chances of conception.

>>MORE: When Am I the Most Fertile?

Does an LH surge always mean ovulation?

While an LH surge is a reliable indicator of ovulation—and therefore your fertile window—it's important to note that an LH surge does not guarantee ovulation in every instance. While uncommon, there can be cases where an LH surge occurs without subsequent ovulation. When does this happen? 

  • Hormonal imbalances: Hormonal imbalances, such as polycystic ovary syndrome (PCOS), can disrupt the normal ovulation process even in the presence of an LH surge.
  • Stress and emotional factors: High levels of stress, emotional turmoil, or significant life events can interfere with ovulation, despite the occurrence of an LH surge.
  • Medications and medical conditions: Certain medications, such as certain types of birth control, and certain medical conditions, such as thyroid disorders, can affect ovulation even if an LH surge is detected. However, it depends on the person—some individuals with thyroid disorders may still ovulate regularly, while others may experience irregular or absent ovulation.
  • Perimenopause or menopause: During the transition to menopause (perimenopause) and in menopause itself, the hormonal fluctuations can lead to irregular ovulation or the absence of ovulation despite an LH surge.

If you have concerns about ovulation or are experiencing irregularities in your cycle, it's recommended to consult with a healthcare professional for a thorough evaluation.

How to detect your LH surge

Detecting your LH surge is crucial for determining your most fertile days. So, how can you do it?

The best way to determine your LH surge is to use a tool that specifically measures the LH in your body. Your doctor can do this with blood tests. You can also do it from the comfort of your home with an ovulation predictor kit, if it measures specifically for LH.

Oova is a fertility tracking device that offers a comprehensive approach to monitoring hormone levels, including the LH surge. It consists of a handheld reader and disposable test strips. Users collect urine samples on the test strips, which are then inserted into the reader for analysis. 



Oova provides quantitative measurements of LH levels and offers a more in-depth understanding of your hormonal patterns, helping you track your fertility more precisely. Oova’s quick results can also help predict the LH surge in advance, allowing you to plan intercourse accordingly. 

LH surge range

If you’re detecting your LH surge, what range should you expect? The typical range of an LH surge can vary between 25-40 international units per liter (IU/L). This surge is considered the normal range and indicates a healthy ovulation process.

However, the LH surge is not a one-size-fits-all phenomenon. The intensity of the surge can vary from person to person and even from cycle to cycle within the same person. When interpreting H surge levels, it’s crucial to take into account an individual's baseline and their specific fertility patterns.

What’s considered a low number in an LH surge?

A low LH surge refers to levels below the expected range, so below 25 IU/L. It could indicate an issue with the timing or quality of ovulation. In some cases, a consistently low LH surge may be associated with conditions such as hypothalamic dysfunction or low ovarian reserve.

What’s considered a high number in an LH surge?

A high LH surge refers to levels above the typical range, around 44.6 IU/L. This may indicate conditions such as PCOS, where the body produces excess LH, or it can be a response to certain medications. A consistently high LH surge without ovulation could affect fertility and may require medical attention.

>>RELATED: How Is Polycystic Ovary Syndrome (PCOS) Diagnosed?

It's important to note that interpreting LH surge levels should be done in conjunction with other fertility signs and under the guidance of a healthcare professional. Monitoring the trends in your LH surge levels over multiple cycles can provide a clearer picture of your individual patterns and help in optimizing your fertility journey. 


Understanding and tracking the LH surge is a key part of optimizing fertility and increasing the chances of successful conception. The LH surge acts as a vital signpost in a woman's menstrual cycle, indicating the optimal time for ovulation and fertilization. Using fertility tracking devices like Oova can provide accurate and detailed measurements of LH levels, empowering individuals with valuable insights into their fertility patterns. 

Remember, the journey to parenthood may have its ups and downs, but understanding the role of the LH surge and utilizing tools like Oova can provide invaluable support on the path to achieving your dreams of starting or expanding your family.

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