Updated by the Progyny Clinical Team — September 2025.
What is luteinizing hormone?
Luteinizing hormone (LH) is made by your pituitary gland and plays a key role in reproduction. LH helps regulate your menstrual cycle and ovulation. A rise in LH — called the LH surge — triggers ovulation.
Why would you have your LH levels checked?
Your LH levels can be measured to determine when you are ovulating. This information can help you plan intercourse if you are trying to become pregnant.
If you are having trouble becoming pregnant, your OB-GYN or reproductive endocrinologist may order an LH test. When measured along with follicle-stimulating hormone (FSH) and estradiol, LH levels give your doctor information about your ovarian reserve.
If you are not ovulating, your LH levels can help identify the cause. For example, LH levels are often elevated in people with polycystic ovary syndrome (PCOS).
LH testing can also be used to:
- Monitor your response to ovarian stimulation.
- Predict the timing of ovulation.
If you have irregular menstrual cycles or do not get a period, your doctor may recommend LH and other hormone testing to look for possible causes.
When should you have LH levels checked?
LH levels are often checked at the beginning of the menstrual cycle — classically Day 3 — along with FSH, to evaluate ovarian function.
More commonly, LH is checked midway through your cycle, since the LH surge triggers ovulation. In a 28-day cycle, this usually happens around Day 14, but timing varies from person to person.
What does the LH test look for?
The LH test measures the amount of luteinizing hormone in your blood or urine.
- High LH levels may be normal if you are in menopause. If you are younger than 40, high LH could suggest premature menopause, PCOS, or certain genetic conditions that affect hormone production. High LH outside of the surge can interfere with ovulation and menstruation, contributing to infertility.
- Low LH levels may prevent ovulation and menstruation, making it harder to become pregnant. Low LH is more common in people with eating disorders, athletes, those experiencing high stress, or individuals with pituitary or hypothalamic disorders.
LH testing is usually done with other hormone tests such as FSH, testosterone, estradiol, and progesterone. Together, these results help determine your next steps.
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Disclaimer: The information provided by Progyny is for educational purposes only and is not medical advice. Always consult a qualified healthcare provider for medical guidance.