The follicle stimulating hormone (FSH) blood test measures the level of FSH in blood. FSH is a hormone released by the pituitary gland, located on the underside of the brain.
Follicle stimulating hormone
How the Test is Performed
A blood sample is needed.
How to Prepare for the Test
If you are a woman of childbearing age, your health care provider may want you to have the test done on certain days of your menstrual cycle.
How the Test will Feel
When the needle is inserted to draw blood, some people feel moderate pain. Others feel only a prick or stinging sensation. Afterward, there may be some throbbing or a slight bruise. These soon go away.
Why the Test is Performed
In women, FSH helps manage a women’s cycle and stimulates the ovaries to produce eggs. The test is used to help diagnose or evaluate:
Being very underweight or having had recent rapid weight loss
Not producing eggs (not ovulating)
Parts of the brain (the pituitary gland or hypothalamus) not producing normal amounts of some or all of its hormones
High FSH levels in men may mean the testicles are not functioning correctly due to:
Advancing age (male menopause)
Damage to testicles caused by alcohol abuse, chemotherapy, or radiation
Problems with genes, such as Klinefelter syndrome
Treatment with hormones
Certain tumors in the pituitary gland
Low FSH levels in men may mean parts of the brain (the pituitary gland or hypothalamus) do not produce normal amounts of some or all of its hormones.
High FSH levels in boys or girls may mean that puberty is about to start.
Veins and arteries vary in size from one patient to another and from one side of the body to the other. Obtaining a blood sample from some people may be more difficult than from others.
Other risks associated with having blood drawn are slight but may include:
Fainting or feeling light-headed
Hematoma (blood accumulating under the skin)
Infection (a slight risk any time the skin is broken)
Borawski D, Bluth MH. Reproductive function and pregnancy. In: McPherson RA, Pincus MR, eds. Henry's Clinical Diagnosis and Management by Laboratory Methods. 22nd ed. Philadelphia, PA: Elsevier Saunders; 2011:chap 25.
Gruber HA, Farag AF. Evaluation of endocrine function. In: McPherson RA, Pincus MR, eds. Henry's Clinical Diagnosis and Management by Laboratory Methods. 22nd ed. Philadelphia, PA: Elsevier Saunders; 2011:chap 24.
Melmed S, Kleinberg D, Ho K. Pituitary physiology and diagnostic evaluation. In: Melmed S, Polonsky KS, Larsen PR, Kronenberg HM, eds. Williams Textbook of Endocrinology. 12th ed. Philadelphia, PA: Elsevier Saunders; 2011:chap 8.
Susan Storck, MD, FACOG, Chief, Eastside Department of Obstetrics and Gynecology, Group Health Cooperative of Puget Sound, Bellevue, Washington; Clinical Teaching Faculty, Department of Obstetrics and Gynecology, University of Washington School of Medicine. Also reviewed by David Zieve, MD, MHA, Bethanne Black, and the A.D.A.M. Editorial team