What is FSH?
FSH is produced by the pituitary gland and stimulates follicle development in the ovaries and sperm production in the testes. It is a key indicator of ovarian and testicular reserve.
FSH on day 2–3 of the menstrual cycle (early follicular phase) is used to assess ovarian reserve in fertility evaluation. A high day-3 FSH is associated with poorer response to fertility treatments.
Why might FSH be low?
Low FSH can prevent ovulation and impair fertility. Causes are similar to low LH — hypothalamic or pituitary dysfunction, eating disorders, or extreme exercise.
This information is educational. A single out-of-range result is rarely the whole picture — a healthcare professional can interpret your numbers alongside your overall health and history.
Context questions that matter
- →Was this result slightly or clearly outside the reference range?
- →Were related markers also high or low?
- →Is this new compared with previous tests?
- →Could recent illness, exercise, fasting, alcohol, supplements, or medication affect it?
- →Do you have symptoms that should be discussed with a clinician?
Questions to ask your doctor
- →Could time of day, cycle phase, stress, sleep, medication or supplements affect this result?
- →How does this compare with related hormones such as LH, FSH, testosterone, estradiol, prolactin, cortisol or DHEA-S?
- →Is this a one-time result, or part of a pattern that needs repeat testing?
Don't guess from one flagged result.
Start with the most relevant panel and see how your markers fit together in plain English.
Frequently asked questions
What does low FSH mean?
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Low FSH can prevent ovulation and impair fertility. Causes are similar to low LH — hypothalamic or pituitary dysfunction, eating disorders, or extreme exercise.
What is FSH?
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FSH is produced by the pituitary gland and stimulates follicle development in the ovaries and sperm production in the testes. It is a key indicator of ovarian and testicular reserve.
Does timing matter for hormone tests?
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Often yes. Time of day, menstrual cycle phase, sleep, acute stress, medications and supplements can all affect hormone results. Morning samples and same-time-of-day repeat testing are typically preferred for hormones with a daily rhythm.
Should hormone results be compared with related hormones?
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Yes — hormones are usually interpreted as patterns. TSH is read with Free T4 and Free T3; testosterone is read with LH, FSH and SHBG; cortisol is read with ACTH and the time of day. Single values out of context can be misleading.