Which Fertility Tests to Ask For, and When to Time Them

A fertility workup can come back "all normal" and still have told you almost nothing, because half of these tests only mean something if they were drawn at the right moment. A progesterone level checked on a fixed calendar day, a thyroid panel drawn without regard to the cycle, a semen analysis collected after three weeks of abstinence — each one can produce a number that looks reassuring or alarming for reasons that have nothing to do with your fertility. If you already know it's time to be evaluated and you already know what to say in the room, the piece that's missing is this: which test, exactly when, and who is even allowed to order it.

Which fertility test should come first, and does the timing really matter that much?

Yes — timing changes whether a result is meaningful at all, not just how precise it is. A semen analysis is usually the first, cheapest, and least cycle-dependent test to run, while nearly every blood test that follows has a specific window in the menstrual cycle, a time of day, or a set of conditions (fasting, recent medication, recent orgasm) that has to be respected for the number to be interpretable. Getting the sequence and timing right the first time is what keeps a workup from having to be repeated a cycle later.

When does progesterone actually need to be drawn, and why does "day 21" get it wrong?

Progesterone is drawn to confirm that ovulation happened and that the luteal phase is producing enough hormone, and it only reflects that if it's drawn roughly 7 days after ovulation — not on a fixed calendar date. "Day 21" assumes a textbook 28-day cycle with ovulation around day 14; if your cycles run 32 or 35 days, a day-21 draw happens before ovulation and can come back low for a completely healthy cycle. The fix is to time the draw to your own signals — a basal body temperature shift, a positive ovulation predictor kit, or a urinary PdG (a progesterone metabolite) test — rather than the calendar. If you're not already tracking those signals, our guide to reading ovulation signs with more confidence covers how to do it well enough to hand a provider a usable timeline. This is typically ordered by an OB-GYN or reproductive endocrinologist, and it's the single most common mistimed test we see among patients coming to us from labs drawn across Long Island before they'd been told the calendar-day assumption doesn't fit every cycle.

When should FSH and estradiol be drawn, and why do they have to be read together?

Early-follicular FSH and estradiol are drawn together on approximately cycle day 2 through 4, while the cycle is still quiet. FSH on its own can look normal even when reserve is diminished, because an elevated estradiol at the same draw can suppress FSH into a falsely reassuring range — reading FSH without estradiol is one of the more common ways this test gets misread. Both are ordered by an OB-GYN or reproductive endocrinologist, usually alongside a same-visit ultrasound for antral follicle count.

Does AMH need to be timed to my cycle at all?

No — anti-Müllerian hormone is one of the few fertility hormones that can be drawn on any day of the cycle, which is part of why it's become a default screening test. The condition that does change an AMH result is hormonal contraception: a randomized comparison of oral, transdermal, and vaginal combined contraceptives found that AMH levels fell significantly across all three routes after continuous use, so a result drawn while on hormonal birth control can read misleadingly low. If your result doesn't match your age or your antral follicle count, ask whether it was drawn on birth control and whether it should be repeated off it. AMH and the antral follicle count (an ultrasound-based test, best done early in the cycle) are usually ordered together by an OB-GYN or reproductive endocrinologist.

What conditions does a prolactin test need to be accurate?

Prolactin should be drawn fasting, in the morning, without recent nipple stimulation or breast exam, strenuous exercise, or significant stress in the hours before the draw — all of these can transiently raise prolactin and produce a false-positive result. Endocrine Society guidance on hyperprolactinemia specifically recommends confirming a single elevated result with a repeat draw under controlled conditions before pursuing pituitary imaging, since a mildly elevated one-off number is common and often not clinically significant. This is ordered by an OB-GYN, endocrinologist, or reproductive endocrinologist, and it is cycle-independent — any day works, as long as the conditions above are met.

When should thyroid labs be drawn, and does it matter what time of day?

TSH, free T4, and thyroid peroxidase (TPO) antibodies are not cycle-dependent, but TSH does have a mild daily rhythm, so a consistent morning draw makes results easier to compare over time if you're repeating the panel. The American Thyroid Association's guideline on thyroid disease in pregnancy and preconception care recommends screening TSH, and free T4 and TPO antibodies when TSH is abnormal or autoimmune thyroid disease is suspected, because both overt and subclinical thyroid dysfunction and thyroid autoimmunity affect ovulation, cycle regularity, and early pregnancy. Your OB-GYN, an endocrinologist, or a reproductive endocrinologist can order this panel; it does not require a specialist referral to get started.

When should testosterone, DHEAS, and 17-hydroxyprogesterone be checked, and what does timing catch?

Total and free testosterone, DHEAS, and sex hormone–binding globulin (SHBG) are drawn in the early follicular phase, in the morning, when androgen levels are at their most stable and interpretable — this panel is typically requested when irregular cycles, acne, or excess hair growth raise the possibility of PCOS, and it sits alongside the ultrasound and cycle criteria used in the Rotterdam definition; our explanation of how PCOS is actually diagnosed covers that fuller picture. A less familiar test that belongs in the same conversation is early-morning, early-follicular 17-hydroxyprogesterone (17-OHP), which screens for non-classic congenital adrenal hyperplasia — a treatable adrenal condition that mimics PCOS on the surface but is missed if 17-OHP isn't drawn at the right time of day, per the Endocrine Society's clinical practice guideline on 21-hydroxylase deficiency. This full panel is usually ordered by an OB-GYN, endocrinologist, or reproductive endocrinologist once PCOS is on the table.

Do fasting insulin, HbA1c, ferritin, and vitamin D need special timing?

Fasting insulin and a fasting glucose or HbA1c need exactly what the name says — a true fast, typically 8 hours, with the blood draw first thing in the morning before food; an oral glucose tolerance test with insulin adds a sugar drink and timed draws afterward and has to be scheduled as its own appointment. Ferritin and vitamin D are not cycle- or fasting-dependent and can be drawn any day alongside almost anything else, which makes them easy to add to a visit that's already happening rather than something to schedule separately. All four can be ordered by an OB-GYN, primary care physician, or endocrinologist; none require a reproductive endocrinology referral.

When in the cycle should an HSG, HyCoSy, or pelvic ultrasound happen?

A hysterosalpingogram (HSG) or hysterosalpingo-contrast sonography (HyCoSy/HyFoSy) — both used to check whether the fallopian tubes are open — need to happen in the early follicular phase, after bleeding has fully stopped but before ovulation, typically cycle day 5 through 10. Earlier in that window avoids flushing contrast or saline through a fresh endometrial lining, and finishing before ovulation avoids disrupting a fertilized egg on the (small) chance conception already happened that cycle. A systematic review and meta-analysis comparing HyFoSy, HyCoSy, and X-ray HSG found comparable diagnostic accuracy for tubal patency across the three, so the choice between them is often about what's locally available and how much discomfort you're willing to tolerate rather than which one is "better." A baseline pelvic ultrasound for the uterus, ovaries, and endometrial lining is more flexible and can usually be done any time bleeding isn't actively obscuring the view, though a same-visit antral follicle count needs the early-follicular window described above for AMH and AFC. These are ordered by an OB-GYN or reproductive endocrinologist, and the referral for HSG/HyCoSy specifically often goes to a radiology or imaging center; several practices around Huntington run this on a scheduled weekly slot, so it's worth asking how far out the earliest early-follicular opening is before you assume it can happen this cycle.

What's the right timing and repeat interval for a semen analysis?

A semen analysis should follow an abstinence window of roughly 2 to 7 days — too short and volume and count can look artificially low, too long and motility tends to decline — and World Health Organization reference values are the standard used to interpret count, motility, and morphology against typical fertile ranges. Because results can vary meaningfully from one sample to the next, a single abnormal result is usually repeated after several weeks rather than treated as final. If the count and motility come back normal but something still doesn't add up — a prior loss, unexplained infertility, or a failed IVF cycle — sperm DNA fragmentation testing looks at a layer a standard semen analysis can't see; our piece on the test a normal semen analysis can miss covers when that conversation comes up. A semen analysis can be ordered by an OB-GYN, urologist, or reproductive endocrinologist, and our male-factor workup overview lays out what a fuller male-factor evaluation adds once a first analysis raises a question. Long Island has enough urology and andrology labs that scheduling shouldn't be the bottleneck; getting the abstinence window right usually is.

Who can actually order each of these tests, and how do I get the workup started this cycle?

Most of this panel does not require a reproductive endocrinologist to begin. An OB-GYN can order progesterone, FSH/estradiol, AMH, AFC, thyroid labs, prolactin, androgens, fasting insulin and glucose, ferritin, vitamin D, and refer for HSG/HyCoSy and a semen analysis. An endocrinologist manages a specific hormonal condition — thyroid disease, PCOS-related insulin resistance, an adrenal issue flagged by 17-OHP — and can order or interpret the labs tied to that condition, but the fertility conversation has to be raised explicitly inside that visit. A reproductive endocrinologist is trained specifically in fertility diagnosis and treatment and is who most of the above gets referred to once a workup stalls, several tests need coordinating quickly, or a specific fertility treatment like IUI or IVF is already on the table. Patients we see in Huntington often arrive with two or three of these tests already drawn at the wrong point in the cycle, which usually just means a short, avoidable delay rather than a real medical problem.

If a provider is willing to test but slow to start, naming the specific test and its timing tends to move things faster than a general request: "Can we get my progesterone timed to my temperature shift this cycle, and my semen analysis and thyroid panel ordered today, so none of it waits for the next visit?" That sentence does the scheduling work for the provider instead of leaving it to a follow-up call. If you're still deciding whether it's time to start this process at all, our guide to when to seek fertility testing, and when not to wait covers that decision in full, and once you're in the room, our list of questions to ask your fertility doctor at every visit covers what to say beyond the tests themselves.

A printable version of the timing rules, test by test:

None of these tests, on their own, tells you why a cycle didn't work or whether the next one will — they tell you whether the number in front of you is even measuring what it claims to measure. Getting the timing right the first time turns a workup from a string of confusing, possibly repeat-worthy results into a real, orderable set of answers, and it's the single most controllable part of a process that otherwise runs on someone else's calendar.

This article is for general educational purposes and is not a substitute for individualized medical care. Testing, diagnosis, genetic screening and any medication decisions belong with your OB-GYN or reproductive endocrinologist, based on your own history.

East to West Fertility is a systems biology fertility clinic in Huntington, Long Island, serving patients across Long Island, NYC, and beyond. Learn more about our Metabolic & Immune Fertility Evaluation or call 631-416-4940.

References:

• Practice Committee of the American Society for Reproductive Medicine. "Diagnostic evaluation of the infertile female: a committee opinion." Fertility and Sterility, 2015;103(6):e44-50.

• Practice Committee of the American Society for Reproductive Medicine. "Testing and interpreting measures of ovarian reserve: a committee opinion." Fertility and Sterility, 2020;114(6):1151-1157.

• Kallio S, Puurunen J, Ruokonen A, Vaskivuo T, Piltonen T, Tapanainen JS. "Antimüllerian hormone levels decrease in women using combined contraception independently of administration route." Fertility and Sterility, 2013;99(5):1305-1310.

• Melmed S, Casanueva FF, Hoffman AR, et al. "Diagnosis and treatment of hyperprolactinemia: an Endocrine Society clinical practice guideline." Journal of Clinical Endocrinology & Metabolism, 2011;96(2):273-288.

• Alexander EK, Pearce EN, Brent GA, et al. "2017 Guidelines of the American Thyroid Association for the diagnosis and management of thyroid disease during pregnancy and the postpartum." Thyroid, 2017;27(3):315-389.

• Speiser PW, Arlt W, Auchus RJ, et al. "Congenital adrenal hyperplasia due to steroid 21-hydroxylase deficiency: an Endocrine Society clinical practice guideline." Journal of Clinical Endocrinology & Metabolism, 2018;103(11):4043-4088.

• Cooper TG, Noonan E, von Eckardstein S, et al. "World Health Organization reference values for human semen characteristics." Human Reproduction Update, 2010;16(3):231-245.

• Xydias EM, Emmanouil V, Koutini M, et al. "Comparison of HyFoSy, HyCoSy and X-Ray Hysterosalpingography in the Assessment of Tubal Patency in Women with Infertility: A Systematic Review and Meta-Analysis." Medical Sciences, 2025;13(3):168.