Fertility Workup: Test Timing and Interpretation Quick-Reference
Written by: Dr. Susan Fox, DACM, L.Ac., FABORM
Credentials: Fertility Coach/Expert, Founder of Health Youniversity
Reviewed/Updated: Sept 2026
Reading Time: 8–10 min read
Medical disclaimer: This FAQ page is general educational and does not replace medical advice from your physician, OB-GYN, reproductive endocrinologist, urologist, midwife, oncologist, or licensed healthcare provider.
A concise, at-a-glance reference for when in the cycle to draw each test and how to interpret the result. Timing matters most for cycle-dependent hormones (FSH, estradiol, progesterone, androgens); several tests can be drawn any day.
Ovulation and Ovulatory-Hormone Testing
Test
Optimal timing
Interpretation / cutoff
Midluteal progesterone
7 days before expected menses (cycle day 21 in a 28-day cycle)
3 ng/mL confirms ovulation occurred
Urine LH surge (home kit)
Late follicular phase, testing daily from cycle day 10
Positive surge ~14 days before menses is confirmatory of impending ovulation
TSH
Any day
Interpret per general-population reference interval; identifies thyroid-related ovulatory dysfunction
Prolactin
Morning, fasting, avoid recent breast/nipple stimulation or exercise
Morning, fasting, avoid recent breast/nipple stimulation or exercise
FSH, LH, estradiol (for anovulation/amenorrhea workup)
Early follicular (cycle day 2–4) if cycling; random if amenorrheic
High FSH + low estradiol → ovarian insufficiency; low/normal FSH + low estradiol → hypothalamic amenorrhea
17-OHP (if PCOS/androgen excess suspected)
Early follicular, morning (8:00–10:00)
Screens for nonclassic 21-hydroxylase-deficient CAH
A woman with regular monthly menses (~every 28 days) is presumed ovulatory, and routine ovulation confirmation is not required.
Ovarian Reserve Testing
Test
Optimal timing
Threshold suggesting low reserve
AMH
Any day (low intercycle variability; cycle-independent)
Low reserve suggested below ~1.0–1.66 ng/mL (assay-dependent); >6 ng/mL suggests PCOS/high response
FSH
Early follicular phase, cycle day 2–4 (peak follicular-phase value)
Adequate <10 IU/L; >10–15 mIU/mL suggests diminished reserve (highly abnormal >15 is specific but insensitive)
Estradiol
Early follicular phase, cycle day 2–4 (interprets FSH)
Adequate <80 pg/mL; day-3 estradiol >60–80 pg/mL associated with higher cancellation and lower pregnancy rates
Antral follicle count (AFC)
Antral follicle count (AFC)
Adequate ≥12; <4 follicles (2–10 mm, both ovaries) suggests low reserve
Age remains the strongest predictor of live birth regardless of these markers, and these tests estimate quantity/response — not oocyte quality.
Androgen Panel (when PCOS or androgen excess suspected)
Test
Optimal timing
Notes
Total/free testosterone, DHEAS, androstenedione (A4), SHBG, 17-OHP
Morning (8:00–10:00), fasting; early follicular (cycle day 2–5) where feasible
Reference ranges derive from fasted early-morning follicular samples; testosterone by LC-MS/MS does not vary much across the cycle, but luteal A4 runs higher
Combined oral contraceptive
Stop ≥3 months before androgen testing (suppresses sex steroids; progestins can cross-react on testosterone immunoassays)
Thyroid (Complete Panel)
TSH — any day; interpret by local general-population reference interval. A single abnormal (mildly elevated) TSH should be repeated with free T4 after 4–6 weeks before diagnosing subclinical hypothyroidism, since many mildly elevated values normalize.
Free T4 — pairs with TSH to distinguish subclinical from overt hypothyroidism.
TPO antibodies — value in identifying euthyroid women at risk of progression to hypothyroidism and with prognostic significance for miscarriage/preterm birth; consider especially with high-normal TSH, recurrent miscarriage, other autoimmune disease, or a first-degree relative with thyroid autoimmunity.
For a woman on levothyroxine planning pregnancy, a preconception TSH target of 0.5–2.5 mU/L is reasonable.
Additional Tests
Test
Timing
Interpretation
Vitamin D (25-OH-D)
Any day
Deficiency <20 ng/mL (associated with reduced fecundability); ≥30 ng/mL generally considered sufficient, with some reproductive data suggesting benefit at higher levels
Iron & ferritin
Any day (ferritin is an acute-phase reactant — interpret with CRP if inflammation suspected)
Iron deficiency common in reproductive-aged women; ferritin <30 µg/L indicates deficiency even without anemia
Semen Analysis (Male Partner)
Abstinence: collect after 2–5 days of abstinence (WHO); transport at body temperature; a febrile illness or antibiotics in the prior 2–3 months can affect results.
Repeat: an abnormal result should be confirmed with a second analysis ≥1 month later, as parameters are highly variable.
WHO lower reference limits (5th percentile):
Parameter
Lower reference limit
Volume
1.5 mL
pH
7.2–7.8
Total count
39 million per ejaculate
Concentration
≥15 million/mL (<15 = oligozoospermia)
Motility
≥40% forward progression (<40% = asthenozoospermia)
Morphology
≥4% normal forms, Kruger criteria (<4% = teratozoospermia)
WBC
<1 million/µL
Total motile count <20 million is significantly associated with lower probability of conception. Values above/below the limits do not by themselves predict fertility or infertility except in azoospermia or severe defects.
Values are cycle-day guidance and reference thresholds; there is no universal consensus on ovarian-reserve cutoffs, and interpretation should be individualized to the patient and local assay.
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About The Author
Dr. Susan Fox
DACM, L.Ac., FABORM
Fertility Coach/Expert, Founder of Health Youniversity
Dr. Susan Fox, DACM, L.Ac., FABORM, is a fertility coach, Doctor of Acupuncture and Chinese Medicine, and Founder of Health Youniversity. She has 24 years of experience supporting women ages 30–45 navigating natural conception, IVF, IUI, PCOS, endometriosis, diminished ovarian reserve, and unexplained infertility. Her work blends Traditional Chinese Medicine, Functional Medicine, fertility education, nutrition, circulation support, lifestyle medicine, and emotional well-being to help women prepare their bodies for conception and pregnancy.
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