Luteinising Hormone (LH) Blood Test: Normal Ranges, Causes & What Your Results Mean

What Is Luteinising Hormone?

Luteinising hormone (LH) is a gonadotrophin - a hormone produced by the anterior pituitary gland in the brain that plays a central role in reproductive function. Together with follicle-stimulating hormone (FSH), LH regulates the function of the ovaries in women and the testes in men.

In women, LH has a particularly dramatic role in the menstrual cycle. During the follicular phase, LH levels remain relatively low while FSH stimulates the development of ovarian follicles. As the dominant follicle matures and oestradiol levels rise, this triggers a sudden, sharp increase in LH, the LH surge, which is the hormonal signal that triggers ovulation. After the egg is released, LH supports the formation and function of the corpus luteum, which produces progesterone to prepare the uterine lining for potential implantation.

In men, LH acts on Leydig cells in the testes to stimulate testosterone production. Adequate LH signalling is essential for normal spermatogenesis, sexual function, and the maintenance of male secondary sexual characteristics.

LH secretion is controlled by the hypothalamic-pituitary-gonadal (HPG) axis through a sophisticated feedback system. Gonadotrophin-releasing hormone (GnRH) from the hypothalamus stimulates LH release, while sex hormones (oestrogen, progesterone, testosterone) feed back to regulate its production - typically through negative feedback, except during the mid-cycle LH surge in women, which is driven by positive oestradiol feedback.

Why Is LH Tested?

LH testing is a cornerstone of reproductive and endocrine investigation. Common clinical indications include:

• Fertility assessment: LH is measured alongside FSH to evaluate ovulatory function in women trying to conceive. The LH:FSH ratio is also relevant in conditions such as polycystic ovary syndrome (PCOS).
• Irregular or absent periods: Amenorrhoea (absent periods) or oligomenorrhoea (infrequent periods) prompts LH testing to determine whether the cause is hypothalamic, pituitary, or ovarian.
• Confirming ovulation: A mid-cycle LH surge confirms that ovulation is occurring. Ovulation predictor kits used at home detect urinary LH.
• Investigating suspected PCOS: An elevated LH:FSH ratio (often greater than 2:1) is characteristic of PCOS, though it is not required for diagnosis.
• Male infertility: LH testing helps distinguish between primary testicular failure (high LH, low testosterone) and secondary hypogonadism (low LH, low testosterone).
• Assessing puberty: In children with early (precocious) or delayed puberty, LH measurement helps determine whether the HPG axis is activated.
• Menopause confirmation: Elevated LH and FSH in the context of amenorrhoea support a diagnosis of menopause or premature ovarian insufficiency.
• Monitoring hormone therapy: LH is tracked in patients undergoing fertility treatment, hormone replacement therapy, or GnRH analogue therapy.

Normal Ranges

LH is measured in international units per litre (IU/L). Normal ranges vary significantly depending on sex, age, and, in women, the phase of the menstrual cycle:

Category	Normal Range (IU/L)	Notes
Women - Follicular phase	2–13 IU/L	Early to mid-cycle
Women - Ovulatory surge	20–90 IU/L	Mid-cycle peak; triggers ovulation
Women - Luteal phase	1–12 IU/L	Post-ovulation
Postmenopausal women	15–60 IU/L	Elevated due to loss of ovarian feedback
Men	2–9 IU/L	Relatively stable throughout adulthood
Children (pre-pubertal)	< 0.5 IU/L	HPG axis not yet activated

It is important to interpret LH results in the context of the menstrual cycle phase (for premenopausal women), other hormone results (particularly FSH, oestradiol, and testosterone), and clinical symptoms. A single LH value in isolation can be misleading due to the hormone's pulsatile secretion and dramatic mid-cycle fluctuations.

What Do High LH Levels Mean?

Elevated LH can indicate a range of reproductive and endocrine conditions:

• Menopause / perimenopause: As ovarian function declines and oestrogen production falls, the pituitary produces more LH (and FSH) in an attempt to stimulate the ovaries. Persistently elevated LH above 25 IU/L alongside raised FSH and amenorrhoea supports menopause.
• Premature ovarian insufficiency (POI): Elevated LH and FSH before age 40 indicates early ovarian failure, with implications for fertility and long-term bone and cardiovascular health.
• Polycystic ovary syndrome (PCOS): Many women with PCOS have an elevated LH:FSH ratio, often exceeding 2:1. This disproportionate LH elevation drives excess ovarian androgen production, contributing to acne, hirsutism, and anovulation.
• Primary hypogonadism (men): Testicular failure from conditions such as Klinefelter syndrome, orchitis, trauma, or chemotherapy results in high LH (the pituitary increases output to try to stimulate failing testes) alongside low testosterone.
• Ovulatory surge: A physiological spike to 20–90 IU/L at mid-cycle is entirely normal and confirms ovulation.
• LH-secreting pituitary adenoma: Rare. A benign pituitary tumour can autonomously produce LH.
• Genetic conditions: Turner syndrome (45,X) in women or Klinefelter syndrome (47,XXY) in men typically cause elevated gonadotrophins.

What Do Low LH Levels Mean?

Low LH levels suggest underactivity of the hypothalamus or pituitary gland, or suppression of the HPG axis:

• Hypothalamic amenorrhoea: A common cause in women - excessive exercise, very low body weight, eating disorders (such as anorexia nervosa), or chronic stress can suppress GnRH secretion, leading to low LH, absent periods, and anovulation.
• Hypopituitarism: Damage to the pituitary gland from tumours, surgery, radiotherapy, or autoimmune conditions (lymphocytic hypophysitis) can reduce LH production alongside other pituitary hormones.
• Hypogonadotrophic hypogonadism: Conditions such as Kallmann syndrome (congenital GnRH deficiency) result in very low LH and FSH, causing delayed puberty and infertility.
• Hyperprolactinaemia: Excess prolactin, commonly from a prolactinoma, suppresses GnRH pulsatility, reducing LH secretion. This can cause menstrual irregularity, galactorrhoea, and infertility.
• Medication effects: GnRH analogues (used in IVF, endometriosis, prostate cancer), combined oral contraceptives, and high-dose opioids suppress LH.
• Severe illness or malnutrition: Acute systemic illness and severe caloric restriction can suppress the HPG axis as a physiological survival mechanism.
• Anabolic steroid use: Exogenous testosterone and anabolic steroids powerfully suppress LH and FSH through negative feedback, often leading to testicular atrophy and infertility in men.

How to Improve Your LH Levels

Approaches to managing LH depend on the underlying cause and whether levels are too high or too low:

If LH Is Low (Hypogonadotrophic Hypogonadism / Hypothalamic Suppression)

• Address lifestyle factors: If hypothalamic amenorrhoea is caused by under-eating or excessive exercise, increasing caloric intake and reducing training intensity can restore HPG axis function. This often requires support from a dietitian and psychologist.
• Achieve a healthy body weight: A BMI below approximately 18.5 is strongly associated with suppressed LH. Gradual weight restoration is often sufficient to restore normal menstrual cycles.
• Manage stress: Chronic psychological stress raises cortisol, which suppresses GnRH. Mindfulness, cognitive behavioural therapy, and lifestyle adjustments can help.
• Treat underlying conditions: Prolactinomas are typically treated with dopamine agonists (cabergoline or bromocriptine), which lower prolactin and allow LH to recover.
• Fertility treatment: Pulsatile GnRH therapy or gonadotrophin injections (containing LH and FSH) can restore ovulation in women with hypogonadotrophic hypogonadism.
• Discontinue suppressive medications: If safe to do so, stopping anabolic steroids or other HPG-suppressing drugs allows natural recovery, though this may take months.

If LH Is High

• PCOS management: Weight loss (if overweight), regular exercise, and dietary improvements can reduce insulin resistance and may help normalise the LH:FSH ratio. Metformin and combined oral contraceptives are commonly used treatments.
• Hormone replacement therapy: For menopausal or POI-related LH elevation, HRT replaces oestrogen and progesterone, which feeds back to suppress LH somewhat while protecting bones and cardiovascular health.
• Address primary gonadal failure: Testosterone replacement in men with primary hypogonadism does not fix the underlying testicular issue but restores normal androgen levels and suppresses LH through negative feedback.

When Should You Get Tested?

Consider an LH blood test if:

• Your periods are irregular, absent, or unusually heavy.
• You are struggling to conceive and want to assess ovulatory function.
• You suspect you may be approaching menopause or experiencing premature ovarian insufficiency.
• You have symptoms of PCOS (acne, excess hair growth, weight gain, irregular cycles).
• You are a man with low libido, erectile dysfunction, fatigue, or reduced muscle mass.
• You are concerned about delayed or precocious puberty in a child or adolescent.
• You are undergoing fertility treatment and need cycle monitoring.
• You have symptoms of a pituitary disorder (headaches, visual changes, galactorrhoea).

For premenopausal women, the timing of the blood draw within the menstrual cycle is critical. Your clinician will typically request testing on days 2–5 (follicular phase) for baseline assessment, or around day 14 for ovulation confirmation.

Which Lola Health Tests Include Luteinising Hormone?

LH is an essential component of reproductive and hormonal health panels. Lola Health includes LH in the following tests:

• Peak Insights - our most comprehensive health screen, including a full hormone profile with LH, FSH, oestradiol, testosterone, and more.
• Hormone 7 - a focused hormonal panel ideal for assessing reproductive health, fertility, and hormonal balance.
• Vital Check — a broad wellness screen covering hormonal, metabolic, and cardiovascular health markers.
• Core Health — an essential health check providing key hormonal and metabolic insights.

All Lola Health tests use venous blood draws for clinical-grade accuracy. Your results are reviewed by qualified healthcare professionals who provide personalised recommendations.