Fertility isn’t a single yes-or-no test. It’s a combination of signals your body gives you every month, blood work that measures your reproductive hormones, and sometimes imaging tests that check for physical blockages. Most people can get a strong picture of their fertility by tracking a few key body signals at home, then confirming with lab tests if needed.
Your Menstrual Cycle Is the First Clue
A regular menstrual cycle, arriving roughly every 24 to 38 days, is one of the simplest signs that your body is likely ovulating. Ovulation is the core event that makes conception possible: your ovary releases an egg, and that egg can be fertilized for about 12 to 24 hours. If your periods come predictably and you notice shifts in your body mid-cycle (breast tenderness, mild cramping on one side, changes in discharge), those are all signs ovulation is probably happening.
Irregular or absent periods don’t automatically mean you’re infertile, but they do suggest your body may not be ovulating consistently. Conditions like polycystic ovary syndrome, thyroid disorders, or high stress levels can disrupt ovulation without eliminating it entirely.
Cervical Mucus Changes During Your Fertile Window
The discharge you notice throughout your cycle isn’t random. It changes in response to rising estrogen levels as your body prepares to ovulate. In the days leading up to ovulation, cervical mucus becomes clear, stretchy (it can stretch about an inch between your fingers), and slippery or lubricative. This is called peak-type mucus, and its presence is one of the most reliable at-home indicators that you’re in your fertile window.
Your most fertile days include the days you observe this peak-type mucus plus the three days after the last day you see it. After ovulation, mucus typically becomes thicker, tackier, or dries up altogether. If you consistently notice this pattern each cycle, it’s a strong sign your hormones are cycling normally and ovulation is occurring.
Basal Body Temperature Confirms Ovulation
Your resting body temperature shifts slightly after ovulation due to a rise in progesterone. The increase is small, typically between 0.4°F and 1°F, so you need a thermometer that reads to two decimal places. Take your temperature at the same time each morning before getting out of bed.
The catch is that basal body temperature only tells you ovulation already happened. It doesn’t predict it in advance. You’ll need to track for at least three full cycles to see the pattern clearly: a cluster of lower temperatures in the first half of your cycle, then a sustained shift upward after ovulation that stays elevated until your next period. If you see that shift consistently, your body is ovulating.
Ovulation Predictor Kits and LH Surges
Over-the-counter ovulation predictor kits (OPKs) detect a surge in luteinizing hormone in your urine. This hormone spikes right before ovulation, and the egg is typically released 28 to 36 hours after the surge begins. That makes OPKs useful for timing, but they also serve as a fertility signal: if you’re getting positive results, your brain is sending the right hormonal trigger for ovulation.
A positive OPK doesn’t guarantee the egg was actually released, since occasionally the body can surge without ovulating. But consistent positive results cycle after cycle, especially combined with a temperature shift afterward, give you high confidence that ovulation is happening.
Blood Tests That Measure Fertility
If you want a clearer picture, a few blood tests can quantify your reproductive health. These are typically ordered by a doctor as part of a fertility workup.
Progesterone is drawn about a week after ovulation (often called a “day 21” test, though the timing depends on your cycle length). A level above 10 ng/mL confirms that ovulation occurred and your body is producing enough progesterone to support a pregnancy. Below that threshold suggests you either didn’t ovulate that cycle or your hormonal support was inadequate.
FSH (follicle-stimulating hormone) is tested early in your cycle, usually day 2 or 3. This hormone tells your ovaries to develop an egg. Levels below 15 mIU/mL are associated with better fertility outcomes. Between 15 and 25, chances decline, and above 25, per-cycle pregnancy rates drop significantly. High FSH can indicate your ovaries are working harder to produce eggs, which often reflects a smaller remaining egg supply.
AMH (anti-Müllerian hormone) estimates your ovarian reserve, meaning how many eggs you have left. Unlike FSH, AMH can be drawn on any day of your cycle. In a large study of nearly 23,000 women, the median AMH at age 25 was 3.3 ng/mL, dropping to 1.4 ng/mL by age 35 and 0.5 ng/mL by age 40. Levels below 1.2 ng/mL are considered diminished ovarian reserve. By age 35, nearly half of women fall below that threshold.
AMH tells you about egg quantity, not egg quality. A low AMH doesn’t mean you can’t get pregnant, but it may mean you have less time and fewer cycles to work with.
Structural Tests for Blockages
Even if your hormones are perfect, a physical blockage can prevent pregnancy. A hysterosalpingogram (HSG) is an X-ray-based test where dye is injected into the uterus and fallopian tubes. If the dye flows freely through both tubes and spills out the ends, the pathway is open. If it stops, there’s a blockage.
The HSG also reveals uterine shape abnormalities (such as a septum dividing the uterine cavity or a bicornuate uterus) and can detect fibroids, polyps, or adhesions. This test is typically part of a formal fertility evaluation rather than something done proactively, but it provides information that no blood test or at-home method can.
Male Fertility Matters Equally
About half of fertility problems involve male factors, so a semen analysis is a critical part of any fertility assessment. The World Health Organization’s current standards set the lower limits for normal results at 39 million total sperm per ejaculate, 42% total motility (meaning sperm that are moving), and 4% normal morphology (meaning sperm shaped correctly). Below these thresholds, conception is still possible but becomes less likely per cycle.
A semen analysis is relatively simple: a sample is collected and examined in a lab, with results usually available within a few days. Because sperm production takes about three months, results can fluctuate based on recent illness, heat exposure, or lifestyle factors. A single abnormal result is often followed up with a repeat test.
How Age Affects Your Per-Cycle Odds
Fertility declines with age, but the decline is more gradual than many people expect until the late 30s. A large North American study tracked per-cycle conception rates and found that compared to women aged 21 to 24, fecundability (the chance of conceiving in any given cycle) was only about 12% lower for women aged 28 to 30, and 18% lower for women aged 34 to 36. The drop becomes steeper after 37: women aged 37 to 39 had 40% lower per-cycle odds, and women aged 40 to 45 had 60% lower odds.
In cumulative terms, about 79% of women aged 25 to 27 conceived within 12 cycles of trying, compared to 75% of women aged 34 to 36 and roughly 56% of women aged 40 to 45. Age matters, but it’s not a cliff at 35. The real acceleration happens closer to 38 or 39.
When to Get a Professional Evaluation
The American Society for Reproductive Medicine recommends a fertility evaluation if you’ve been having regular unprotected sex for 12 months without conceiving and you’re under 35. If you’re 35 or older, that timeline shortens to 6 months. For women over 40, earlier evaluation is warranted given the steeper decline in per-cycle odds.
Certain signs justify evaluation sooner regardless of age: cycles shorter than 21 days or longer than 40 days, no periods at all, a history of pelvic infections, endometriosis, or prior surgeries involving the reproductive organs. For male partners, a history of undescended testes, prior chemotherapy, or known hormonal issues also warrants earlier testing.