Your fertility isn’t a single number, but you can get a surprisingly clear picture by combining a few key indicators: your age, your cycle patterns, hormone levels, and lifestyle factors. Some of these you can track at home starting today, while others require a blood test or clinic visit. Here’s how to piece together what your body is telling you.
Age Is the Strongest Single Predictor
No other factor affects fertility as much as age, particularly for women. A woman in her early to mid-20s has a 25 to 30% chance of conceiving in any given month. By 40, that drops to around 5% per cycle. The decline isn’t sudden. It’s a gradual slope that steepens after 35, driven by both a shrinking egg supply and a higher rate of chromosomal abnormalities in remaining eggs.
Male fertility also declines with age, though more slowly. Sperm quality, including motility and DNA integrity, tends to decrease after the mid-40s. Age alone doesn’t determine your fertility, but it sets the baseline that everything else modifies.
What Your Menstrual Cycle Reveals
Regular cycles between 21 and 35 days are a strong signal that you’re ovulating consistently. Irregular, very long, or absent periods suggest ovulation may not be happening reliably, which directly reduces your chances of conceiving in any given month.
You can get more specific by tracking two things at home. First, basal body temperature: your resting temperature rises by about half a degree after ovulation and stays elevated until your next period. Charting this over two or three cycles shows whether you’re ovulating and roughly when. Second, cervical mucus changes throughout your cycle in a predictable pattern. It starts dry or sticky after your period, becomes creamy, then watery, and finally stretchy and slippery like raw egg whites. That egg-white consistency marks your most fertile window, typically one to two days before ovulation.
If you see both a temperature shift and egg-white mucus each cycle, you have good evidence that ovulation is happening. If you never notice the egg-white stage or your temperature chart is flat, that’s worth investigating further.
Hormone Tests That Measure Egg Supply
The most useful blood test for estimating your remaining egg supply is AMH (anti-Müllerian hormone). Unlike most fertility hormones, AMH stays relatively stable throughout your cycle, so it can be drawn on any day. General ranges to know:
- Average: 1.0 to 3.0 ng/mL
- Low: Under 1.0 ng/mL
- Severely low: 0.4 ng/mL or below
AMH declines naturally with age. At 25, a typical level is around 3.0 ng/mL. By 35, it drops to roughly 1.5 ng/mL, and by 40 it’s around 1.0 ng/mL. A result that’s low for your age suggests a smaller-than-expected egg reserve, while an unusually high result can sometimes point to polycystic ovary syndrome (PCOS).
An important caveat: AMH tells you about egg quantity, not egg quality. A 28-year-old with a low AMH may still have excellent egg quality, while a 42-year-old with a normal AMH still faces age-related quality decline. It’s one piece of the puzzle, not the whole picture.
Confirming That You Ovulate
Home ovulation predictor kits detect a surge in luteinizing hormone (LH), which triggers egg release. A positive result means ovulation is likely within 12 to 36 hours. These kits work well for most people, but if your cycles are irregular or you have a condition like PCOS that causes chronically elevated LH, the results can be unreliable.
The most definitive confirmation is a blood progesterone test, drawn about seven days after suspected ovulation. Progesterone rises sharply after the egg is released, and levels in the range of 2 to 25 ng/mL during this phase confirm that ovulation occurred. Your doctor can order this as a simple, single blood draw.
At-Home Fertility Kits: What They Can and Can’t Do
Several mail-order kits now test hormones like AMH, FSH, and others from a finger-prick blood sample. Many advertise 99% accuracy, but that number comes from controlled lab conditions. In practice, results can be less reliable. If your hormone levels fall outside typical ranges (which is exactly the scenario you’d want to catch), these tests become less accurate than advertised.
At-home FSH tests, for example, measure whether your body is working harder than normal to stimulate your ovaries. A high reading can suggest a lower egg reserve, but as fertility specialists note, these readings alone don’t provide enough information to understand what’s really happening with your eggs. They can cause unnecessary worry or offer false reassurance. Use at-home kits as a screening tool, not a diagnosis. Abnormal results should always be followed up with clinical testing.
How Male Fertility Is Assessed
Fertility is a two-person equation in about half of all cases where couples struggle to conceive. A semen analysis is the standard test, and it’s straightforward: a sample is collected and examined under a microscope. The World Health Organization’s current reference values set the bar at a sperm concentration of at least 16 million per milliliter, total motility (the percentage of sperm that are moving) of at least 42%, and normal shape in at least 4% of sperm.
Falling below any of these thresholds doesn’t mean conception is impossible, but it does reduce the odds per cycle. Results can fluctuate based on recent illness, heat exposure, stress, and the time since last ejaculation, so a single abnormal result is usually repeated before drawing conclusions.
Lifestyle Factors That Shift the Odds
Weight has a measurable impact on conception rates. A BMI under 18.5 is associated with difficulty getting pregnant, largely because low body fat can disrupt ovulation. On the higher end, excess weight increases estrogen production and can similarly interfere with regular ovulation. Reaching a BMI in the 19 to 24 range, when possible, removes one variable from the equation.
Smoking accelerates egg loss and reduces sperm quality. Heavy alcohol intake suppresses reproductive hormones in both sexes. Chronic stress raises cortisol, which can delay or prevent ovulation. None of these factors are absolute barriers, but each one nudges monthly conception odds downward. The encouraging flip side: improving any of them can nudge odds back up, sometimes within a few months.
When to Get a Professional Evaluation
The American Society for Reproductive Medicine recommends that women under 35 who have been trying for 12 months without success get a formal fertility evaluation. For women 35 and older, that timeline shortens to 6 months. For women over 40, earlier evaluation is reasonable given the steeper decline in monthly odds.
These timelines assume no known red flags. If you already have a condition linked to infertility, such as endometriosis, PCOS, a history of pelvic infections, or very irregular periods, testing should start right away rather than waiting out the clock. The same applies if a male partner has a known issue like undescended testicles or prior chemotherapy.
A standard workup for women typically includes AMH and other hormone levels, an imaging study to check whether the fallopian tubes are open, and an ultrasound to look at ovarian follicle count. For men, it starts with a semen analysis. Together, these tests identify a cause in the majority of cases and help determine what, if anything, to do next.