When to Test Hormones: Timing Your Lab Work

Hormone levels fluctuate throughout your cycle, day, and even hour. Testing at the wrong time can give misleading results.

Menstrual Cycle Timing

Days 1-5 (Early Follicular)

Best for baseline hormones:

• FSH
• LH
• Estradiol
• Testosterone
• DHEA-S
• AMH (any time)

Days 19-21 (Luteal Phase)

Best for:

• Progesterone (peaks mid-luteal)
• Estrogen/progesterone ratio

Any Day

• Thyroid hormones
• Vitamin D, B12, iron
• Metabolic markers

Time of Day

Morning (before 9am)

• Cortisol (peaks in early morning)
• Testosterone (highest in morning)
• Fasting glucose and insulin

Any Time

• Most other hormones
• Vitamins and nutrients

Special Circumstances

Perimenopause

Hormones fluctuate unpredictably. Test early follicular phase if still cycling, or any time if periods are irregular.

On Birth Control

Hormonal contraceptives suppress natural hormone production. Testing may not reflect your true levels.

Postmenopause

Hormones can be tested any time.

References

• Practice Committee of the American Society for Reproductive Medicine. (2015). Diagnostic evaluation of the infertile female: a committee opinion. Fertility and Sterility, 103(6), e44-e50.
• Harlow, S. D., et al. (2012). Executive summary of the Stages of Reproductive Aging Workshop + 10: addressing the unfinished agenda of staging reproductive aging. Journal of Clinical Endocrinology & Metabolism, 97(4), 1159-1168.
• Rosner, W., et al. (2007). Position statement: utility, limitations, and pitfalls in measuring testosterone. Journal of Clinical Endocrinology & Metabolism, 92(2), 405-413.