Luteinizing Hormone (LH) by Immunoassay (Serum)

Why Is This Test Done? This blood test measures the amount of luteinizing hormone (LH) in your body. LH helps control the reproductive system: it triggers ovulation in women and supports testosterone production in men. Your doctor may order it to help evaluate fertility concerns, irregular or missed periods, symptoms of menopause, early or delayed puberty, low testosterone, or a possible problem with the pituitary gland.

Your healthcare provider may order an LH test to evaluate reproductive function, diagnose hormonal imbalances, or monitor conditions such as polycystic ovary syndrome (PCOS), infertility, or pituitary disorders. It can also be part of screening for certain cancers or thyroid issues.

What to Expect Before the Test: In most cases, no special preparation is needed, and you can eat and drink normally before your appointment. Tell your doctor about all medicines, vitamins, and supplements you take, especially hormonal birth control, hormone therapy, or corticosteroids, because these can affect your LH level. If you menstruate, the blood draw may need to happen at a specific point in your cycle, so ask whether timing matters. Wearing a short-sleeved shirt can make the draw easier.

No special preparation is usually needed, but you may be asked to fast for 8–12 hours before the test if it’s part of a broader hormonal panel. Bring any medications you’re currently taking to your appointment.

What Happens During the Test? A trained technician will wrap an elastic band around your upper arm, clean the skin, and draw a small sample of blood from a vein, usually in your arm. You may feel a quick pinch or sting, and the whole process usually takes only a few minutes. Afterward, a small bandage or cotton pad is placed on the spot, and your sample goes to a laboratory for analysis. You can return to your normal activities right away.

A healthcare professional will draw blood from a vein in your arm using a small needle. You may feel a brief pinch, but it’s usually over quickly. The blood sample is then sent to a lab for analysis.

What Are the Results? Your report will show how much LH is in your blood compared with a reference range. Normal values vary widely depending on your age, your sex, and, for women, the phase of the menstrual cycle, so your doctor will interpret your numbers alongside your symptoms and other hormone tests such as FSH. If your level falls outside the expected range, your doctor will explain what it may mean and whether additional testing or follow-up is needed.

Results are typically reported in international units per liter (IU/L) or milliliters per liter (mIU/L). Your results will be compared to standard reference ranges provided by your lab and discussed with your doctor.