Received your baseline lab results with little explanation? Here's your guide to optimal ranges:

FSH

• What is FSH: Follicle-stimulating hormone is produced by the pituitary gland (the master endocrine gland) and plays a key role in stimulating follicles and supporting ovarian function. Baseline levels help assess whether FSH is effectively communicating with the ovaries.

• Best day to test? Cycle days 2-4, with day 3 being ideal

• Optimal: 3–5 mIU/mL

• Good: 6-9 mIU/mL

• Further Investigation: > 12 mIU/mL

• Note: It’s important to consider FSH and E2 together due to their inverse relationship, as well as the FSH:LH ratio—a key PCOS marker.

LH

• What is LH? Luteinizing hormone is produced by the pituitary gland. While FSH supports follicular development, LH plays a critical role in triggering ovulation. Because LH is part of a feedback loop with FSH and E2, healthy LH levels—measured alongside the others—can provide clues about early ovarian activity, PCOS, and possible hypothalamic or pituitary dysfunction.

• Best day to test? Cycle days 2-4, with day 3 being ideal

• Normal range: 1.9-12.5 mIU/mL or <7 mIU/mL on day 3

Estradiol (E2)

• What is E2? E2 is the primary form of estrogen in non-pregnant women of reproductive age. Maturing follicles produce rising E2 levels, which suppress FSH and signal an increase in LH. E2 supports numerous functions, including menstruation, ovulation, and the proliferation of the uterine lining. It also protects the vaginal and gut microbiome.

• Best day to test? Cycle days 2-4, with day 3 being ideal

• Normal baseline range: 25-75 pg/ml (or less than 80 pg/ml)

• Range at time of HCG trigger (IVF cycle): 1000-4000 pg/ml

• Note: Low E2 can falsely elevate FSH, while high E2 can falsely lower it. E2 and FSH should always be interpreted together.

AMH

• What is AMH? Anti-Müllerian hormone is produced by granulosa cells of small growing ovarian follicles. AMH is used to estimate ovarian reserve and guide IVF stimulation protocols, but it does not predict natural fertility status or egg quality.

• Best day to test? Any day of the cycle (or alongside day 3 labs for convenience)

• Normal range: >1 ng/mL is good; >3 ng/mL may be considered high

• Note: AMH is age-dependent, and optimal ranges vary. Many studies—including those published by the NIH and ASRM—have found that AMH is not a predictive value for natural pregnancy and that low AMH levels are not associated with reduced fertility.

Prolactin

• What is Prolactin? Prolactin is produced by the pituitary gland and supports milk production postpartum. When levels are too high outside of the postpartum period, it can interfere with ovulation and menstrual regularity.

• Best day to test? Usually tested with FSH, LH, and E2 on days 2–4

• Normal range: 5-19 ng/mL

• Further Investigation: >25 ng/mL

Keep in mind:

If one or more of your results is out of range, remember:

Hormones do not exist in a vacuum. No single result will define or predict your fertility.

Baseline hormones are useful for guiding IVF protocols, but they provide only a snapshot of your broader hormonal picture. Other labs to consider:

• Sex Hormone Binding Globulin (SHBG)

• Testosterone (total and free)

• Full Thyroid Panel: TSH, Free T3, Free T4, Total T3, Total T4, TPO, TgAb

• Vitamin D

Always contact your doctor with questions, or reach out to learn more.