What are the normal serum estradiol (E2) concentrations for a healthy premenopausal 34‑year‑old woman during each phase of the menstrual cycle?

Normal Estradiol Levels for a 34-Year-Old Woman

For a healthy 34-year-old premenopausal woman, normal serum estradiol (E2) levels vary dramatically by menstrual cycle phase: early follicular phase 31–771 pmol/L (approximately 8–210 pg/mL), late follicular phase 104–1742 pmol/L (approximately 28–474 pg/mL), ovulation peak 275–2864 pmol/L (approximately 75–780 pg/mL), and mid-luteal phase 151–1941 pmol/L (approximately 41–529 pg/mL). 1

Phase-Specific Reference Ranges

The menstrual cycle creates profound fluctuations in estradiol that make interpretation impossible without knowing the exact cycle day when blood was drawn 2, 1:

Follicular Phase

• Early follicular (days -15 to -6): 31–771 pmol/L or approximately 8–210 pg/mL 1
• Late follicular (days -5 to -1): 104–1742 pmol/L or approximately 28–474 pg/mL 1
• Estrogen rises progressively as the dominant follicle matures during this phase 2

Ovulatory Phase

• LH peak (day 0): 275–2864 pmol/L or approximately 75–780 pg/mL 1
• Peak estrogen levels on days 12–14 trigger the LH surge that induces ovulation 2

Luteal Phase

• Early luteal (days +1 to +4): 95–1188 pmol/L or approximately 26–324 pg/mL 1
• Mid-luteal (days +5 to +9): 151–1941 pmol/L or approximately 41–529 pg/mL 1
• Late luteal (days +10 to +14): 39–1769 pmol/L or approximately 11–482 pg/mL 1
• Estrogen rises again during mid-luteal phase alongside progesterone 2

Critical Interpretation Principles

A single estradiol value can be completely normal or profoundly abnormal depending solely on cycle timing. 2 To properly interpret any result, you must document:

• Exact cycle day when blood was drawn (counting from first day of last menstrual period) 2, 3
• Regularity of menstrual cycles (cycle length 21–35 days is normal) 3
• Hormonal contraceptive use (which suppresses endogenous estradiol production) 3

When to Investigate Further

Estradiol levels below 20 pg/mL in a premenopausal woman warrant immediate investigation for functional hypothalamic amenorrhea or premature ovarian insufficiency, regardless of cycle phase. 2, 3, 4 This threshold is approximately 4-fold below even the lowest expected early follicular phase values 3.

Specific clinical scenarios requiring workup include 3:

• Menstrual irregularities: Amenorrhea >6 months, oligomenorrhea, or polymenorrhea 3
• Infertility: Inability to conceive after 12 months of unprotected intercourse 3
• Estrogen deficiency symptoms: Hot flashes, vaginal dryness, or bone pain 3
• Hyperandrogenism signs: Hirsutism, acne, or male-pattern hair distribution 3
• Galactorrhea or symptoms of hyperprolactinemia 3

Common Pitfalls to Avoid

Never interpret estradiol levels in isolation without menstrual cycle context. 2, 3 A level of 50 pg/mL could represent normal early follicular phase, abnormally low ovulatory phase, or pathologically low mid-luteal phase—the clinical significance changes entirely based on timing 2.

Do not assume amenorrhea alone indicates low estrogen or ovarian failure. 4 Women on certain medications (particularly GnRH agonists) may have amenorrhea with variable estradiol levels requiring high-sensitivity assays for accurate assessment 4.

For equivocal results or persistent concerns, repeat testing with FSH and LH on cycle days 3–6 provides the most reliable assessment of ovarian reserve and function 3.