Understanding Hormonal Blood Tests
FSH, LH, estrogen, progesterone — what the numbers mean
When and Why You Might Need Hormonal Testing
Your doctor might order hormonal blood tests for irregular periods, difficulty conceiving, suspected PCOS, perimenopause, thyroid issues, or other hormonal imbalances.
Timing matters enormously — the same test on day 3 versus day 21 gives very different results, and both could be normal for that day. Your doctor should specify when to have blood drawn.
Don't be afraid to ask your doctor to explain results in plain language.
The Key Hormones and Their Roles
FSH: Stimulates follicle growth. Tested on day 2-3. Normal early-cycle levels: 3-10 IU/L. Higher levels can indicate diminished ovarian reserve.
LH: Triggers ovulation. Baseline (day 2-3): 2-15 IU/L. Elevated LH-to-FSH ratio can indicate PCOS.
Estradiol (E2): Primary estrogen. Early-cycle: 25-75 pg/mL. Rises throughout the follicular phase, peaking before ovulation.
Progesterone: Tested around day 21. Above 3 ng/mL confirms ovulation. Above 10 ng/mL indicates a robust luteal phase.
Other Important Tests
AMH: Can be tested any cycle day. Reflects ovarian reserve (number of eggs remaining). Naturally declines with age.
Thyroid hormones (TSH, Free T3, Free T4): Both hypothyroidism and hyperthyroidism can cause irregular periods and fertility issues.
Prolactin: Elevated levels can suppress ovulation and cause irregular or absent periods.
Testosterone and DHEA-S: Tested when PCOS is suspected or there are signs of excess androgen.
Making Sense of Your Results
A single number in isolation tells you very little. Your doctor considers cycle day, age, symptoms, medical history, and how the hormones relate to each other.
Reference ranges vary between laboratories. A result just outside the range isn't necessarily cause for alarm.
If results are abnormal, your doctor may want to repeat the test or order additional tests. Don't panic about a single set of results.
Keep copies of all test results. Over time, tracking hormonal levels across multiple tests reveals trends that are much more informative than any single snapshot.
Continue reading
- What Is a Normal Cycle Anyway?— 5 min read
- How Stress Affects Your Cycle— 5 min read
- Birth Control and Your Cycle— 6 min read
Quick Tip
Ask your doctor exactly which cycle day to have blood drawn — hormonal test timing matters enormously for accurate results.
This content is for educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always consult your healthcare provider with questions about your health.
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