LH Surge and Ovulation Tests: How to Identify Your Fertile Days

Author's imageby Philomena Marx•18 January 2025
LH Surge and Ovulation Tests

Do you want to better understand your body, keep a closer eye on your cycle, or are you planning a pregnancy? Then you’re in the right place. In this post, you will learn all about the LH surge and its central role in ovulation. We will show you how to recognise it, which tests can support you, and the factors that influence your fertility.

Your Cycle at a Glance: The Four Phases in Brief

The female cycle goes through four phases that work harmoniously together:

  • Menstruation: At the start of the cycle, the built-up uterine lining is shed.
  • Follicular Phase: Under the influence of Follicle Stimulating Hormone (FSH), several follicles develop in the ovaries until one dominant follicle remains.
  • Ovulation: A sharp rise in Luteinising Hormone (LH) triggers the release of the egg from the dominant follicle. Typically, this is the most fertile day.
  • Luteal Phase: The remaining follicle transforms into the corpus luteum and produces progesterone. This hormone prepares the uterine lining for a possible implantation.

Why Hormones Are Crucial: Focus on LH

Hormones act as the timekeepers of your cycle, regulating follicle development, ovulation, and the maintenance of a possible pregnancy. Some key players include:

  • oestrogen and progesterone: Regulate the building and maintenance of the uterine lining.
  • FSH (Follicle Stimulating Hormone): Stimulates the growth of follicles.
  • LH (Luteinising Hormone): Signals the onset of ovulation. When it rises sharply, the release of the egg is imminent.

The LH Surge: What Exactly Happens?

Behind the Scenes in Your Body

Once a follicle has matured and the egg is “ready to leap”, the body releases a large amount of LH in a short period. This surge triggers processes that break down the follicle wall and release the egg into the fallopian tube.

When and for How Long?

  • Onset: About 35–44 hours before ovulation, the LH level starts to rise.
  • Peak: The LH peak occurs approximately 10–12 hours before ovulation.
  • Duration: The elevated LH level lasts for about 12–24 hours before it declines again.

Ovulation Symptoms: How to Recognise Your Fertile Phase

In addition to the LH surge, your body signals the approaching ovulation through various signs:

  • Mittelschmerz: One-sided, cramping or stabbing lower abdominal pain caused by the rupture of the follicle.
  • Cervical Mucus Changes: The mucus becomes clear, stretchy, and egg-white-like, making it easier for sperm to travel.
  • Basal Temperature Rise: Shortly after ovulation, the basal body temperature increases slightly – useful for retrospectively determining the time of ovulation.
  • Increased Libido: Some women experience a heightened sexual desire.

LH Tests: How to Use Them, Tips, and Research Findings

How LH Tests Work

Ovulation tests measure the concentration of LH in the urine through an immunological reaction. A visible test line indicates that the LH level has exceeded a specific threshold.

  • Control Line: Confirms that the test has been performed correctly.
  • Test Line: Once a certain intensity is reached, it indicates that ovulation is imminent.

Practical Tips

  • Fixed Testing Time: Try to test daily at the same time if possible.
  • Fluid Intake: Urine that is too concentrated or overly diluted can affect the result.
  • Follow Manufacturer’s Instructions: Each test kit may have slight differences in handling and interpretation.

Scientific Evidence

Studies show that when used correctly, LH tests are very reliable. Ovulation generally occurs about 20 hours after a positive result. Additionally, sperm can survive up to five days in a woman’s body, further extending the fertile window.

Technical Aids: Other Methods for Cycle Tracking

  • Basal Temperature Measurement: A traditional method to detect the temperature rise after ovulation.
  • Cervical Mucus Analysis: By observing the mucus, you can determine when you are most fertile.
  • Apps and Wearables: Modern applications offer automated cycle tracking and reminder systems.

Hormonal Disorders: Impacts and Solutions

Occasionally, the LH surge may be absent or insufficient. The following causes are common:

  • PCOS (Polycystic Ovary Syndrome): Follicles develop irregularly, and the LH level is often persistently elevated.
  • Thyroid Problems: An underactive or overactive thyroid can disrupt the entire hormonal balance.

If you suspect a hormonal disorder, it is important to seek medical advice to discuss individual treatment options.

In Fertility Treatment: Targeted Use of LH Tests

In reproductive medicine procedures such as IVF (In Vitro Fertilisation) or ICSI (Intracytoplasmic Sperm Injection), LH tests are an integral part: they enable doctors to determine the optimal timing for hormone injections and egg retrievals, thereby increasing the chances of success.

Conclusion

With the knowledge of the LH surge and supportive methods like ovulation tests, you can accurately identify your fertile days. Pay attention to your body’s signals, use smart aids, and seek medical advice if you notice any irregularities. This way, you remain well-informed about your fertility and can make decisions with confidence.

Frequently Asked Questions (FAQ)

LH is a hormone produced by the pituitary gland in the brain. It plays a key role in ovulation, as a sudden surge (the so-called LH peak) triggers the release of the egg from the ovary. Without a sufficient LH surge, successful ovulation cannot occur.

The most clear indication is a positive ovulation test (LH test). In addition, physical signs such as clear, stretchy cervical mucus, a cramping sensation in the lower abdomen (mittelschmerz), or a rise in basal body temperature may indicate that ovulation is imminent.

It is best to perform the test daily at the same time starting from the middle of your cycle. A moderate fluid intake is advised to ensure that your urine is neither too diluted nor too concentrated. Also, read the manufacturer’s instructions carefully, as different tests may have slight variations in procedure.

A negative result despite ovulation is rare, but it can happen if you miss the timing of the LH surge or if your urine is too diluted. Hormonal fluctuations or incorrect test administration can also affect the result.

A positive LH test indicates that your body is signalling for ovulation. In most cases, ovulation then occurs within the next 24 to 36 hours. However, in hormonal disorders such as PCOS, an LH surge may be detected without actual ovulation taking place.

Stress can disrupt the delicate hormonal balance, delaying or weakening the LH surge. Therefore, try to reduce stressful situations and ensure you get enough rest, especially if you are trying to conceive.

If an LH surge is absent for several cycles, this may indicate anovulation. In such cases, it is advisable to seek medical advice to rule out hormonal disorders or other causes.

Yes. Combining LH tests with basal temperature measurement (the symptothermal method) or cervical mucus observation increases accuracy, as you can monitor multiple signs of your fertile phase. Technical aids such as cycle tracking apps can also provide additional support.

Minor fluctuations are normal. Factors such as stress, diet, sleep patterns, and physical activity can affect your cycle. As long as ovulation occurs regularly and your cycle does not vary greatly, these fluctuations are generally harmless.

Women with Polycystic Ovary Syndrome (PCOS) often have an elevated LH level relative to FSH. This can result in LH tests showing positive more frequently, even when ovulation does not occur. It is very important to seek medical evaluation and treatment for PCOS.

In many fertility clinics, LH tests are used in conjunction with treatments to determine the optimal timing for procedures such as insemination or egg retrieval. It is best to discuss the protocol with your treating doctor.

A balanced diet, sufficient exercise, minimising stress, and optimising the timing of intercourse around ovulation are effective ways to increase the chances of a successful conception.

After a positive LH test, it is advisable to have intercourse promptly – ideally within the next 24 hours. Since sperm can survive for up to five days in the body, it is recommended to have regular intercourse in the days leading up to the expected LH surge.

A cycle can shift due to factors such as stress, travel, or diet, which may cause the LH surge to occur earlier or later than expected. If such shifts occur regularly, it may indicate a hormonal imbalance. A medical consultation can provide clarification.