LH Surge: When To Detect Peak Fertility With An OPK | RMA Network

skip to main content ⚠️ Winter Storm Notice: View Office Closures & Updates

Blog

LH Surge: When to Detect Peak Fertility with an OPK Table of Contents What is Luteinizing Hormone (LH)? What is an LH surge? Luteinizing Hormone and Fertility Frequently Asked Questions about Luteinizing Hormone (LH) and Fertility Am I ovulating? Find out with urinary LH surge testing. Understanding OPK Results OK, I saw an LH surge. Now what? When should I see a fertility specialist? A Word from RMA Network

This article explains the significance of the luteinizing hormone (LH) surge in the ovulation cycle and how ovulation predictor kits (OPKs) can help detect this surge. By understanding the timing of the LH surge, individuals can identify their most fertile window, optimizing the chances of conception. Fertility Specialists from RMA Network provide valuable insight on when to detect peak fertility.

While ovulation predictor kits (OPKs) are a great tool for helping couples learn more about their fertile period, it’s essential to understand the science behind how they work.

Keep reading to learn about OPKs, how these test kits work, and the best ways to identify peak fertility.

What is Luteinizing Hormone (LH)?

Luteinizing Hormone (LH) is a reproductive hormone produced by the pituitary gland that plays a key role in the menstrual cycle and fertility. In women, a surge in LH levels triggers ovulation—the release of a mature egg from the ovary—usually around the middle of the cycle. This surge marks the most fertile window, making LH a critical marker for identifying peak fertility. In men, LH supports the production of testosterone and sperm.

LH plays different roles throughout life and across sexes. In women, LH levels rise sharply just before ovulation, acting as a signal that the dominant egg is ready for release. This hormonal shift is part of a carefully timed communication between the brain and ovaries.

In men, LH supports the function of the testes by promoting steady testosterone production, which is vital for sperm development and overall reproductive health.

In children, LH contributes to the development of sexual organs and triggers puberty-related changes by stimulating estrogen production in girls and testosterone in boys. Its function evolves across life stages, making LH a central hormone in reproductive health for all genders.

What is an LH surge?

An LH surge is a rapid increase in luteinizing hormone levels around 24-48 hours before ovulation. This surge is a reliable indicator of a woman’s fertile window, making it the ideal time for couples trying to conceive to have unprotected sex.

Unlock the Key to Boosting Fertility Naturally

Download our free eBook to discover the essential vitamins that support female fertility and improve your chances of conceiving.

How do I know when LH peaks?

Although there aren’t any physical “symptoms” of an LH surge, LH can be detected and measured through ovulation predictor kits (OPKs), which can be bought online or over the counter at most drug stores. These kits work by detecting LH levels in a woman’s urine.

LH levels can also be measured through a blood test.

Women who are ovulating may also experience changes in their cervical mucus and a slight increase in their basal body temperature (BBT).

How long does the LH surge last?

An LH surge begins about 36 hours before ovulation and lasts roughly 24 hours. However, the exact duration may vary from person to person.

LH Surge: When to Detect Peak Fertility with an OPK

Can I have two LH surges?

While it’s rare, some studies suggest having two or more LH peaks in one cycle is possible. This is known as hyperovulation or multiple ovulation. It occurs when both ovaries release an egg or when more than one egg is released during a single ovulatory cycle.

Hyperovulation can result in giving birth to fraternal twins or multiple pregnancies, increasing a person’s risk for high blood pressure, preterm labor, and other complications.

According to the American Society for Reproductive Medicine (ASRM), naturally, women have a one in 250 chance of giving birth to twins and one in 10,000 chance of giving birth to triplets. However, these odds may increase with fertility treatments or due to hereditary factors.

What if I never see a surge?

Women who are unable to detect an LH surge shouldn’t panic. There are several reasons for delayed ovulation, including:

• stress
• certain medications (e.g., antidepressants, steroids, thyroid medications, chemo, etc.)
• breast feeding
• polycystic ovary syndrome (PCOS)
• perimenopause or menopause
• age and weight

Another possibility is that the surge isn’t meeting the specific LH volume threshold required by the ovulation predictor kit. But this doesn’t mean a woman isn’t surging or ovulating.

In this case, a low-threshold OPK may be more suitable. Women who consistently struggle to detect LH should contact their fertility doctor or reproductive endocrinologist for further guidance and evaluation. They’ll be able to determine the underlying cause and suggest appropriate treatment options to induce ovulation and improve the chances of conception.

LH Surge Chart

Luteinizing Hormone and Fertility

Understanding the role of the luteinizing hormone (LH) is crucial for couples trying to get pregnant. By tracking their LH levels and identifying the surge, couples can effectively time intercourse or fertility treatments to coincide with ovulation, increasing their chances of conceiving.

Frequently Asked Questions about Luteinizing Hormone (LH) and Fertility

Below, we answer some of the most frequently asked questions about LH and fertility.

How soon after an LH peak will I ovulate?

Ovulation occurs between eight and 20 hours after an LH peak.

But the real answer to this question is: It depends. Every woman and her reproductive system is unique, so there’s no one-size-fits-all timeframe.

How long does LH stay elevated after ovulation?

The duration of an LH surge is different for each woman. LH levels typically return to their baseline within 24-48 hours.

How often should I test for ovulation?

It’s recommended to test for ovulation once daily. However, many women track their ovulation and LH patterns multiple times daily on the expected surge to know precisely when they’re peaking.

When is the best time of day to test for ovulation?

There’s no wrong or right time to test for ovulation. Though some women prefer to take a urine test in the morning, others find it more helpful to test later in the day or the evening.

That said, it’s important to note that liquid can dilute the amount of LH in the urine. If it becomes too diluted, it can affect the test results. (This is why many women test as soon as they wake up!) To get the most accurate results, avoid drinking fluids two hours beforehand.

When should I start testing every month?

Again, every woman is different! Generally, women with a 28-day cycle (ovulation on Day 14) should begin daily OPK testing on Day 10 and continue until they see an LH surge. Women with a 24-day cycle (ovulation on Days 10-11) should start testing on Day 6 until they surge.

Approximately 16.32% of women have a 28-day cycle. However, most women do not ovulate smack dab in the middle of their cycle. For this reason, it’s important for couples trying to get pregnant to track their menstrual period and observe ovulation signs such as cervical mucus changes and BBT fluctuations. This can help them determine their fertile days and the best time for intercourse, increasing the likelihood of conception and successful pregnancy.

Am I ovulating? Find out with urinary LH surge testing.

There are multiple ways to determine whether or not a woman is ovulating. One effective method is urinary LH surge testing via OPKs, which involves measuring the level of LH in a woman’s urine to detect the hormonal surge preceding ovulation. (Note: Urinary LH surge tests are not ovulation tests; OPKs predict when a woman might ovulate.)

Other ways to calculate a woman’s fertile days include:

• Observing cervical mucus changes: A woman’s cervical mucus changes throughout the menstrual cycle. It becomes wetter, more transparent, and more slippery during ovulation.
• Tracking basal body temperature (BBT): Immediately after ovulation, BBT slightly rises due to increased progesterone levels.
• Tracking the menstrual cycle: Ovulation typically occurs between Day 12 and 16 of a 28-day menstrual cycle, but cycle length can vary from woman to woman. A period-tracking app or calendar can help women pinpoint their unique ovulation window more accurately.

What are OPKs?

OPKs, or ovulation predictor kits, are simple, easy-to-use tests that help women identify their most fertile days by detecting the levels of LH in their urine. These tests resemble pregnancy tests and contain a substance that turns red if an LH threshold is met.

Like pregnancy tests, either one or two lines will turn red; the control, to know whether the test is working, will always turn red, and the LH test line will only appear red if an LH surge is detected. It’s important to follow the instructions provided with each specific OPK brand, as results can vary slightly depending on the manufacturer.

Understanding OPKs: Cost, Accuracy, and Reliability

OPKs do not test for ovulation. Instead, these tests measure the levels of LH in a woman’s urine, which helps predict when ovulation will occur.

OPK Cost & Accessibility

OPKs are relatively affordable and can be found online and at most drug stores. Prices vary depending on the brand but typically range from $15 to $30. Wearables and high-tech devices (e.g., fertility monitors) run between $100 and $300.

Are OPKs accurate?

Yes, OPKs predict ovulation and a woman’s fertile window fairly accurately.

Understanding OPK Results

Interpreting OPK results is pretty straightforward. If the LH test line is as dark or darker than the control line, it indicates a positive result. This line is usually red.

What Does a Positive Ovulation Test Mean?

A positive ovulation test indicates that a surge in LH has been detected in your urine. This hormonal surge signals that ovulation is likely to occur soon, typically within 12 to 48 hours.

OPKs are designed to catch this LH surge so you can identify your most fertile window. When results are positive, it means your body is preparing to release an egg, and the chances of conception are highest during this time.

It’s important to note that a positive ovulation test does not confirm ovulation has already happened. Instead, it predicts that ovulation is approaching, allowing individuals and couples to time intercourse or fertility treatments appropriately.

How to Tell If Your Ovulation Test Is Positive

Most OPKs display results using lines or digital symbols. In traditional line-based tests, a positive ovulation test occurs when:

• The LH test line is as dark as or darker than the control line
• This change often happens quickly, sometimes within hours

A faint LH line does not indicate a positive result. Many people see lighter test lines earlier in their cycle as LH gradually rises, but ovulation is only predicted once LH reaches its peak.

Because the LH surge can be brief, testing once or twice daily as ovulation approaches may help avoid missing your positive result.

What to Do After a Positive Ovulation Test

Once you see a positive ovulation test, timing becomes critical. Since ovulation usually occurs within the next one to two days:

• Have unprotected intercourse as soon as possible
• Continue for the next two to three days
• This timing helps ensure sperm are present when the egg is released

Keep in mind that sperm can survive in the reproductive tract for up to five days, while the egg survives for only 12–24 hours after ovulation. Acting quickly after a positive result maximizes the chances of conception.

Can You Get a Positive Ovulation Test and Not Ovulate?

In some cases, yes. Certain conditions, such as polycystic ovary syndrome, hormonal imbalances, or perimenopause, can cause elevated LH levels without leading to ovulation.

If you consistently see positive ovulation tests but are unsure whether ovulation is occurring, a fertility specialist can confirm ovulation through bloodwork or ultrasound monitoring and help determine the best next steps.

I see a pink LH line – am I surging?

On Days 12 and 13 of a woman’s cycle, seeing a faint LH line on the OPK is not unusual. On Day 14, the line may appear bright red; on Day 15, it may begin to fade again before completely disappearing on Day 16 (which may be the actual day of ovulation). This fluctuation is normal and referred to as the LH surge curve — up, up, peak, down, down.

This curve moves much faster for some women, who could have a pink line in the morning and a bright red line that evening.

Why do I see an LH peak during pregnancy?

It’s possible to see an LH peak during pregnancy because both LH and hCG (human chorionic gonadotropin, the hormone detected in pregnancy tests) share a similar protein structure. So, a pregnant woman who takes an OPK would test positive, but not because she’s about to ovulate; it’s because she’s pregnant.

A woman experiencing an LH surge will not get a positive pregnancy test result. That’s because hCG is the same protein structure as LH, plus a few other proteins. Cool, right?

OK, I saw an LH surge. Now what?

Once an LH surge is detected, it’s time to seize the opportunity and try to conceive! This requires a bit of math. Since ovulation happens 12-48 hours after a positive OPK and an ovulated egg lives between 12-24 hours (and sperm lives for as long as five days), couples should have unprotected sex as soon as an LH peak is detected and for the next three days afterward.

Are OPKs worth it?

OPKs are a great idea for some couples, but they’re not everyone’s cup of tea. However, when paired with knowledge about one’s menstrual cycle and cervical discharge, they can make a great addition to a couple’s fertility journey.

When should I see a fertility specialist?

Women who are 35 or older and have been trying for six months to get pregnant without birth control should see a fertility specialist. Women aged 35 or younger should see a specialist after trying for one year without success. However, if you are already aware or suspicious of a possible problem conceiving or if your periods are irregular in a way that you cannot predict ovulation even with OPKs, it would be helpful to see a specialist sooner rather than later. Remember that each woman’s body is different, and conception can take time. Don’t be discouraged if you don’t see immediate results!

If you’re looking for more information on OPK, read our blog comparing at-home fertility tests to the testing you would get in person at a fertility clinic.

A Word from RMA Network

At RMA Network, we understand that the journey to parenthood can be challenging, but we’re here to support and guide you every step of the way. Our team of experienced fertility specialists is committed to providing personalized care and state-of-the-art treatment options, ensuring the best possible outcomes for our patients.

Marcus W. Jurema

PHYSICIAN PARTNER,REPRODUCTIVE ENDOCRINOLOGIST

Dr. Marcus Jurema is a board-certified Reproductive Endocrinologist at Reproductive Medicine Associates (RMA). “Family has always been an important factor in my personal life and decisions,” he says. “They inspire me to treat my own patients with that same compassion.” Dr. Jurema grew up in Brazil and speaks fluent Portuguese and Spanish.

Egg Freezing in San Francisco & Silicon Valley: A Guide for Women in Tech

IVF and Your Commute: A Guide to Accessible Fertility Care in the Bay Area

Why RMA Northern California Palo Alto is the Best Fertility Clinic in Silicon Valley

Speak to a Fertility Specialist & Get Started

Submit the form for an appointment. For immediate new patient scheduling, call 866-762-3140.

Call to ScheduleRequest We Call YouSchedule Your First Visit866-762-3140

Existing patients with inquiries, please call your local office or send a message via the Artemis Patient Portal.