Quick answer: FSH (follicle-stimulating hormone) is made by the pituitary gland and stimulates egg development in women and sperm production in men. FSH rises as ovarian reserve declines, so it is used to help assess perimenopause, menopause and fertility. Low FSH can point to pituitary or hypothalamic issues. In women, FSH is usually tested early in the cycle.
Key takeaways
FSH is a pituitary hormone that signals the ovaries to develop eggs and the testes to make sperm.
It tends to rise as ovarian reserve declines, so it is often used when looking at perimenopause, menopause and fertility.
Cycle day, age, hormonal birth control and low energy intake can all change FSH, which is why the timing of the test matters.
What is FSH?
FSH is a pituitary hormone that signals the ovaries to develop follicles and the testes to produce sperm.
Why FSH matters
FSH matters for egg development and ovulation and for sperm production. It is also used in assessing ovarian reserve and menopause, and in evaluating fertility.
Understanding your result
Reference ranges vary by lab, age and sex. Your provider interprets your result against the lab’s range and your overall picture, rather than chasing a single number. Functional labs are optional. They can be helpful in more complex cases.
What low FSH can mean
- Hypothalamic amenorrhea (from under-eating, stress or over-exercise)
- Pituitary disorders
- PCOS (FSH may be low relative to LH)
What high FSH can mean
High FSH can reflect declining ovarian reserve or perimenopause, menopause, or primary ovarian insufficiency. In men, it can point to testicular issues.
What affects FSH
FSH is affected by cycle day, age, hormonal birth control, and stress and energy availability.
Ways to support healthy levels
Eat enough to support your activity level, and manage stress and sleep (see natural hormone balance). Discuss fertility testing such as AMH with your provider, and avoid smoking, which affects ovarian function.
What does the research show about FSH?
The Study of Women’s Health Across the Nation (SWAN) followed 3,302 women aged 42 to 52 with yearly blood tests and mapped hormone changes in 1,215 women who reached a natural final period. FSH began rising about 6.1 years before the final period, sped up about 2 years before it, and leveled off about 2 years after, while average estradiol did not change until about 2 years before the final period and then fell, stabilizing about 2 years after. Obesity softened and delayed the FSH rise. Because hormones were drawn only once a year, the study shows group patterns, not the day-to-day swings that make a single result hard to read in perimenopause. (Randolph et al., 2011)
In 2,311 SWAN participants followed with yearly bone scans, spine bone density fell by 5.6% over 4 years in women who went through natural menopause. FSH levels and how they changed over time predicted bone loss better than estradiol, and estradiol below 35 pg/mL was linked with lower bone density but yearly estradiol changes did not predict loss. The findings are associations and apply to women in the menopausal transition. (Sowers et al., 2006)
FSH can swing widely from cycle to cycle in perimenopause, so a single value is a snapshot. In men, FSH is usually read alongside LH and testosterone.
FSH and healthy aging
Rising FSH reflects ovarian aging and the reproductive transition, and it accompanies hormone changes that affect bone, heart and brain.
Related tests and articles: LH, .
When to see a naturopathic doctor
It may be time to see a naturopathic doctor if you have irregular cycles or perimenopause symptoms, or if you are trying to conceive. The same is true if you have missed periods, or for men with fertility concerns.
See a medical provider promptly for no period for three months (after ruling out pregnancy), severe headaches with vision changes, or milky nipple discharge.
FSH at a glance
| Topic | What the article explains |
|---|---|
| Why it matters | Egg development and ovulation; sperm production; assessing ovarian reserve and menopause; and evaluating fertility |
| What can affect it | Cycle day; age; hormonal birth control; and stress and energy availability |
| Supportive habits discussed | Eat enough to support your activity level; manage stress and sleep; discuss fertility testing such as AMH with your provider; and avoid smoking, which affects ovarian function |
Questions to bring to your clinician
These questions can help you get the most out of your next visit.
Which of my other results would help put my FSH result in context?
What might my FSH be telling us, given my health history and symptoms?
Which other labs would be worth pairing with my FSH to get a clearer picture?
When would it make sense to recheck my FSH, and what could I work on in the meantime?
Frequently asked questions
What does high FSH mean?
In women it often reflects declining ovarian reserve or menopause.
When should FSH be tested?
Usually on cycle day 2 to 4 in cycling women.
Can FSH identify menopause?
It can support the picture, but menopause is usually identified by symptoms and 12 months without a period.
Does birth control affect FSH?
Yes. Hormonal birth control suppresses FSH.
Sources
- Gordon CM, et al. Functional Hypothalamic Amenorrhea: An Endocrine Society Clinical Practice Guideline. J Clin Endocrinol Metab 2017. PMID: 28368518. https://pubmed.ncbi.nlm.nih.gov/28368518/
- Harlow SD, et al. Executive summary of the Stages of Reproductive Aging Workshop + 10: addressing the unfinished agenda of staging reproductive aging. J Clin Endocrinol Metab 2012. PMID: 22344196. https://pubmed.ncbi.nlm.nih.gov/22344196/
- Randolph JF, et al. Change in follicle-stimulating hormone and estradiol across the menopausal transition: effect of age at the final menstrual period. J Clin Endocrinol Metab 2011. PMID: 21159842. https://pubmed.ncbi.nlm.nih.gov/21159842/
- Santoro N. Perimenopause: From Research to Practice. J Womens Health (Larchmt) 2016. PMID: 26653408. https://pubmed.ncbi.nlm.nih.gov/26653408/
- Sowers MR, et al. Hormone predictors of bone mineral density changes during the menopausal transition. J Clin Endocrinol Metab 2006. PMID: 16403818. https://pubmed.ncbi.nlm.nih.gov/16403818/
- Teede HJ, et al. Recommendations From the 2023 International Evidence-based Guideline for the Assessment and Management of Polycystic Ovary Syndrome. J Clin Endocrinol Metab 2023. PMID: 37580314. https://pubmed.ncbi.nlm.nih.gov/37580314/
- MedlinePlus: FSH Levels Test
- NICHD: Infertility
This article is for educational purposes only and is not medical advice. It does not replace an individual evaluation. Talk with your healthcare provider before starting supplements or changing medications, especially if you are pregnant, nursing, or managing a health condition.
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