What Is Luteinizing Hormone (LH)?

What it is

LH is a pituitary hormone that surges sharply just before ovulation.

Why it matters

Detecting the LH surge predicts ovulation ~24–36 hours later, supporting fertility tracking.

Specimen

Urine

Interpretation

Surge = ovulation expected within ~24–36 h (fertile window).

Limitations

Surge timing varies; individual cycle patterns differ.

Related test: LH Ovulation Rapid Test — specimen: Urine

Frequently Asked Questions

What does an LH surge mean? Ovulation is expected within about 24–36 hours — the fertile window.

Related knowledge

• Pregnancy & fertility