LH (Luteinizing Hormone)

Luteinizing Hormone (LH) is a pituitary hormone that plays a central role in reproductive function. In women, it triggers ovulation and supports the formation of the corpus luteum, which produces progesterone during the second half of the menstrual cycle. In men, LH stimulates the testes to produce testosterone. This test measures the level of LH in a simple blood sample and is typically requested when investigating fertility concerns, menstrual irregularities, suspected pituitary disorders, or symptoms of hormonal imbalance such as low libido, fatigue, or unexplained changes in cycle length.

Who this test is for

• Women investigating irregular or absent periods, difficulty conceiving, or suspected polycystic ovary syndrome (PCOS).
• Men with symptoms of low testosterone, such as reduced sex drive, erectile dysfunction, or unexplained fatigue.
• Individuals being monitored during fertility treatment or hormone therapy.
• Anyone with suspected pituitary or hypothalamic dysfunction affecting reproductive hormones.

What it screens for

• Ovulatory function: LH surges just before ovulation, so measuring LH helps assess whether ovulation is occurring and can support timing for conception.
• Pituitary function: Abnormal LH levels may indicate pituitary or hypothalamic disorders affecting reproductive hormone signalling.
• Hormonal imbalances: LH is interpreted alongside other hormones such as follicle-stimulating hormone (FSH), oestradiol, progesterone, and testosterone to build a full picture of reproductive health.
• PCOS and related conditions: In some cases, an elevated LH-to-FSH ratio can support the investigation of PCOS.

Why it matters

LH is a key part of the hormonal conversation that governs fertility and reproductive health. Measuring it gives clinicians a clearer view of how the pituitary and gonads are communicating, which can guide diagnosis and treatment decisions. Whether you are trying to conceive, investigating symptoms, or monitoring treatment, an accurate LH result provides essential context for your care.

• Luteinizing hormone (LH)

No special preparation required.

For blood tests, we recommend drinking plenty of water beforehand to ensure smooth sample collection. If you are taking any regular medication, continue to do so unless advised otherwise by your doctor.