Luteinizing hormone (LH) plays a crucial role in the reproductive health of both women and men. When hormone-related issues arise, such as irregular periods, infertility, or low libido, a blood test for luteinizing hormone is often one of the first diagnostic tools a healthcare provider will use.
What Is Luteinizing Hormone (LH)?
Luteinizing hormone is produced by the pituitary gland, located at the base of the brain. It plays a different but equally important role in both sexes:
- In women, LH triggers ovulation, the release of an egg from the ovary, and stimulates the production of progesterone, which prepares the uterus for possible pregnancy.
- In men, LH stimulates the Leydig cells in the testes to produce testosterone, essential for sperm production and male reproductive function.
Because LH levels rise and fall depending on the body’s reproductive stage or hormonal balance, testing its levels provides valuable insight into fertility and endocrine health.
What Is a Blood Test for Luteinizing Hormone?
A blood test for luteinizing hormone measures the amount of LH circulating in your blood. It is typically done in conjunction with other hormone tests, such as follicle-stimulating hormone (FSH), estradiol, testosterone, or progesterone, to provide a complete picture of reproductive and hormonal health.
Reasons for Ordering an LH Blood Test
Your healthcare provider might order a luteinizing hormone LH test for several reasons:
To investigate the causes of infertility
- To evaluate menstrual irregularities
- To diagnose or monitor polycystic ovary syndrome (PCOS)
- To assess puberty disorders
- To check for hypogonadism (low function of testes or ovaries)
- To evaluate pituitary gland function
Blood Test LH Levels: What’s Normal?
LH levels are typically measured in international units per liter (IU/L), but the normal range can vary depending on age, gender, and phase of the menstrual cycle.
Normal LH Levels in Women
- Life Stage or Phase LH Level (IU/L)
- Follicular phase (start of cycle) 1.9 – 12.5 IU/L
- Mid-cycle (ovulation) 8.7 – 76.3 IU/L
- Luteal phase (after ovulation) 0.5 – 16.9 IU/L
- Postmenopausal 15.9 – 54.0 IU/L
Normal LH Levels in Men
- Age Group LH Level (IU/L)
- Adult men 1.5 – 9.3 IU/L
These reference ranges can vary slightly by lab, so always consult your doctor for interpretation of your specific results.
Understanding Low LH Levels
Low LH Levels in Females
Low LH levels in females can signal several reproductive and hormonal issues:
- Hypothalamic amenorrhea: Often caused by stress, low body weight, or excessive exercise
- Pituitary gland disorders: Tumors or damage affecting hormone production
- Polycystic ovary syndrome (PCOS): May show low or inconsistent LH levels, especially if FSH is also low
- Menopause: As women approach menopause, LH levels typically increase, but failure to do so may indicate dysfunction
Common symptoms include:
- Irregular or absent periods
- Difficulty getting pregnant
- Fatigue and mood swings
- Low libido
Low LH Levels in Males
Low LH levels in males can be linked to:
- Hypogonadism: Reduced function of the testes
- Pituitary disorders: Affecting hormone secretion
- Obesity or chronic illness: May suppress hormonal function
- Kallmann syndrome: A rare genetic condition affecting puberty
Symptoms in men may include:
- Decreased muscle mass
- Erectile dysfunction
- Infertility
Low energy or mood changes
If LH is low and testosterone is also below normal, this usually confirms hypogonadism due to pituitary or hypothalamic dysfunction
What Causes High LH Levels?
On the flip side, elevated LH levels may also point to specific health concerns.
In Women:
- Primary ovarian failure (as in premature menopause)
- Turner syndrome (a chromosomal disorder)
- Menopause (naturally causes an LH rise)
- PCOS (often shows a high LH to FSH ratio)
In Men:
- Primary testicular failure
- Klinefelter syndrome (genetic disorder causing infertility)
- Chemotherapy or radiation exposure affecting testes
High LH levels typically indicate that the pituitary gland is working properly but the gonads (ovaries or testes) are not responding adequately.
How Is the LH Test Performed?
- The LH blood test is simple and non-invasive:
- A healthcare provider draws blood from a vein in your arm.
- No special preparation is usually required.
- Women may need to time the test with their menstrual cycle (usually day 2–3 or mid-cycle).
- Results are typically available within 1–2 days.
Interpreting Results: What Do They Mean?
In Women Trying to Conceive:
- A mid-cycle LH surge indicates that ovulation is likely to occur soon.
- No surge may mean ovulation is not happening (anovulation), which can make conception difficult.
In Men with Fertility Concerns:
- Low LH and low testosterone suggest a problem with the hypothalamus or pituitary gland.
- High LH and low testosterone suggest an issue with the testes themselves.
What to Do if LH Levels Are Abnormal?
If your blood test LH levels are outside the normal range, your healthcare provider may recommend:
- Additional hormone testing (FSH, estrogen, testosterone, progesterone)
- Imaging studies (MRI or CT scans) of the pituitary gland
- Genetic testing (for suspected syndromes)
- Fertility evaluation
- Lifestyle modifications (stress reduction, weight management)
Treatment Options
Treatment depends on the cause and symptoms of abnormal LH levels:
For Women:
- Hormone therapy: Estrogen or progesterone supplements for menstrual regulation
- Ovulation induction medications (e.g., Clomiphene) for fertility
- Lifestyle changes: Weight loss, stress management
- Treating underlying conditions: Such as thyroid disease or PCOS
For Men:
- Testosterone replacement therapy (TRT)
- Clomiphene citrate or hCG injections to stimulate sperm production
- Addressing pituitary tumors or disorders if applicable
The blood test for luteinizing hormone is a vital diagnostic tool for evaluating reproductive and hormonal health in both men and women. Whether you are dealing with fertility challenges, irregular periods, or low testosterone, understanding your blood test LH levels is a critical first step. Abnormal results, whether low LH levels in females or low LH levels in males, should prompt further investigation to determine the root cause and guide appropriate treatment.
