FSH (Follicle Stimulating Hormone) is a blood test that measures fsh (follicle stimulating hormone) levels in the blood. Normal range: In women, FSH varies across the cycle and is usually measured on day 2-3: roughly 3-10 IU/L in the early follicular phase, with a mid-cycle peak. Menopausal levels rise above ~25-30 IU/L. In men, FSH is fairly steady at about 1.5-12 IU/L. Ranges are assay-specific.. It is commonly used to helps evaluate fertility, reproductive disorders, and menopausal status..
What is FSH (Follicle Stimulating Hormone)?
A pituitary hormone that stimulates egg and sperm production.
Why is it measured?
Helps evaluate fertility, reproductive disorders, and menopausal status.
Normal Reference Range
In women, FSH varies across the cycle and is usually measured on day 2-3: roughly 3-10 IU/L in the early follicular phase, with a mid-cycle peak. Menopausal levels rise above ~25-30 IU/L. In men, FSH is fairly steady at about 1.5-12 IU/L. Ranges are assay-specific.
Note: Reference ranges may vary between laboratories. Always consult your healthcare provider for interpretation.
What Causes High FSH?
High FSH means the pituitary is working hard to stimulate gonads that are not responding — a sign of primary gonadal failure. In women this most commonly indicates menopause or perimenopause, or, when it occurs before 40, primary ovarian insufficiency. In men, high FSH points to testicular failure (impaired sperm production). Genetic conditions such as Turner syndrome (women) and Klinefelter syndrome (men) also raise FSH.
What Causes Low FSH?
Low FSH suggests the signal from the brain (hypothalamus or pituitary) is reduced — hypogonadotropic hypogonadism. Causes include pituitary tumours or damage, high prolactin, significant weight loss, over-exercise or eating disorders (hypothalamic suppression), and suppression from anabolic steroid or testosterone use, which switches off the body's own FSH and LH. Low FSH with low sex hormones warrants pituitary assessment.
How Often Should FSH Be Tested?
In women being assessed for fertility or cycle problems, FSH is drawn on day 2-3 of the menstrual cycle, usually with LH and oestradiol. For suspected menopause, timing is less critical. In men it is part of a hypogonadism or infertility work-up. It is repeated only as clinically needed.
Related Blood Markers
FSH is almost always interpreted with LH and oestradiol (women) or testosterone (men). AMH and an antral follicle count add detail on ovarian reserve, and prolactin is checked when both FSH and LH are low.
Key Facts
- •Category: Hormone Health
- •Unit of Measurement: IU/L
- •Test Code: FSH
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