While ovulation predictor kits (OPKs) are a great tool to help couples know 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)?
The luteinizing hormone (LH) helps control the menstrual cycle and triggers ovulation in women. Once a dominant egg is mature enough for ovulation, the brain signals the pituitary gland to release LH into the bloodstream.
In men, LH stimulates testosterone production, which is essential for maintaining sperm production and sexual function. LH levels typically remain stable in men, but in women, they fluctuate throughout the menstrual cycle, reaching peak levels around the time of ovulation.
In children, LH plays a vital role in developing reproductive organs and the onset of puberty. In girls, LH signals the ovaries to make estrogen; in boys, it signals the testes to produce testosterone. Children also have LH present in their bodies.
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.
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.
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.
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, there are slight rises in BBT 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.
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 am I seeing 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.
