There’s no single age when every woman should get her hormones checked. Hormone testing is driven by symptoms, not by a birthday. If you’re experiencing irregular periods, unexplained weight changes, difficulty getting pregnant, severe fatigue, or new symptoms that don’t have an obvious explanation, those are the signals that warrant a closer look at your hormone levels. The timing also matters: when in your menstrual cycle you get tested, whether you’re on birth control, and what specific concern you’re investigating all change which tests are useful and when they’ll be accurate.
Symptoms That Warrant Hormone Testing
The most common reason to check hormones is a noticeable change in how your body is functioning. Irregular periods, including cycles that are unusually long, short, heavy, or absent altogether, are one of the clearest signals. Several hormones work together to regulate your cycle, so a disruption in any one of them can throw things off. Conditions like polycystic ovary syndrome (PCOS) and thyroid disorders are frequent culprits.
Other symptoms that point toward a hormonal issue include persistent acne or excess facial and body hair (signs of elevated androgens), unexplained weight gain, chronic fatigue, hair thinning, mood changes that feel disproportionate, night sweats, vaginal dryness, and low sex drive. Excess cortisol and low thyroid hormones can both contribute to weight gain that doesn’t respond to diet and exercise changes. None of these symptoms are diagnostic on their own, but a cluster of them, especially when they’re new and persistent, gives your provider a reason to order bloodwork.
Trying to Get Pregnant
If you’ve been trying to conceive for 12 months without success (or 6 months if you’re over 35), a fertility evaluation typically includes hormone testing. Hormonal imbalances are the leading cause of infertility in women, often because they interfere with ovulation.
A standard fertility workup checks several hormones. FSH and estradiol, measured together on cycle days 2 through 4, help distinguish between different causes of missed or absent periods. High FSH with low estradiol suggests the ovaries are struggling to respond, while normal or low FSH with low estradiol points to a signaling problem from the brain. Anti-Müllerian hormone (AMH), which gives an estimate of your remaining egg supply, can be drawn on any day of your cycle. Thyroid-stimulating hormone (TSH) is also part of the standard panel because untreated thyroid problems can impair fertility even when everything else looks normal.
Progesterone testing comes later in the cycle, typically between days 17 and 21. A level above 3 ng/mL is considered strong evidence that you ovulated that month. If your periods are irregular or absent and your FSH and estradiol are normal, your provider will likely screen for PCOS, which is diagnosed when at least two of these three criteria are present: irregular or absent ovulation, signs of excess androgens (either visible symptoms or elevated testosterone on bloodwork), and a characteristic appearance of the ovaries on ultrasound.
Perimenopause and Menopause
This is where hormone testing gets less straightforward. If you’re in your 40s and experiencing hot flashes, sleep disruption, irregular periods, or mood shifts, you might expect a blood test to confirm you’re in perimenopause. In reality, routine hormone testing during the menopausal transition is not recommended for most women. Ovarian function fluctuates so dramatically during this phase that a single blood draw can look completely normal one week and abnormal the next. Current guidelines recommend managing perimenopausal symptoms based on their frequency and severity rather than chasing lab values.
Hormone testing becomes more useful once periods have stopped entirely. An FSH level of 30 IU/L or higher, combined with 12 consecutive months without a period, is generally considered confirmation of menopause. But even then, many providers will make the diagnosis based on age and symptoms alone without ordering bloodwork.
Where testing does help in this age group is ruling out other conditions that mimic perimenopause. Thyroid disorders are especially common in women over 40 and can cause fatigue, weight changes, mood swings, and cycle irregularities that look identical to early menopause. A TSH test can separate the two quickly.
When in Your Cycle to Test
Hormone levels shift throughout your menstrual cycle, so the day you get your blood drawn matters. Testing on the wrong day can produce results that look abnormal when they’re actually fine, or normal when something is genuinely off.
For baseline reproductive hormones like FSH and estradiol, the early follicular phase (days 2 through 4 of your cycle, counting from the first day of your period) gives the most reliable snapshot. Estradiol correlates best with your overall levels when measured around days 9 through 11, but for fertility purposes, the early-cycle reading paired with FSH is more clinically useful. Progesterone should be tested during the second half of your cycle, ideally around day 20 or 21, when it peaks after ovulation.
Some hormones don’t depend on cycle timing. AMH, TSH, prolactin, and testosterone can all be drawn at any point. If you’re not sure where you are in your cycle because your periods are irregular, your provider can still test these and may draw the cycle-dependent hormones at whatever point you come in, then repeat them later if needed.
Testing on Hormonal Birth Control
If you’re on the combined pill, a patch, or a ring, your FSH, LH, estradiol, and progesterone levels will be suppressed by design. That’s how these methods prevent pregnancy. Testing these hormones while on combined contraception won’t tell you anything useful about your natural baseline, and the concept of a “day 21 progesterone” doesn’t apply because you’re not ovulating.
You can still get meaningful results for thyroid function, prolactin, testosterone, and general health markers while on hormonal birth control. But if your provider needs to see your natural ovarian hormone levels, you’ll need to be off the pill for a cycle or more first. Estrogen-containing contraceptives also raise the proteins that carry thyroid hormones in your blood, which can make total thyroid levels look artificially high. In this case, your provider should order TSH along with free T4 rather than total T4 to get an accurate picture.
Blood Tests vs. Other Methods
Standard blood draws remain the default for hormone testing. They’re well-validated, widely available, and covered by insurance. The main limitation is that a blood sample captures a single moment in time, and some hormones (cortisol especially) fluctuate throughout the day.
Saliva testing is sometimes marketed as a more convenient alternative, and it does have a niche role. It’s useful for measuring the cortisol awakening response, a pattern of cortisol release in the first 30 minutes after waking that can’t be captured by blood or urine. But saliva doesn’t accurately represent the production rates of most other cortisol-related compounds.
Dried urine testing collects multiple samples over 24 hours and provides an integrated picture of hormone production throughout the day. It avoids the inconvenience of the traditional 24-hour urine jug, which studies have found to be inaccurate over 30% of the time due to incomplete collection. Dried urine strips are more practical, but this method is less commonly used in conventional medical settings and may not be covered by insurance.
How to Prepare for Hormone Blood Work
Most hormone panels don’t require fasting, though your provider may ask you to fast if they’re also checking metabolic markers like blood sugar or insulin at the same time. What does matter, and what many people don’t realize, is biotin. If you take a biotin supplement at doses above 1 mg per day (common in hair, skin, and nail formulas), it can interfere with a wide range of hormone assays. Depending on the lab’s testing platform, biotin can produce falsely high or falsely low results for thyroid hormones, FSH, LH, estradiol, progesterone, testosterone, and cortisol. Stop taking biotin at least 48 hours before your blood draw.
Cortisol testing typically requires a morning draw, since levels are highest shortly after waking and drop throughout the day. For other hormones, morning appointments are generally preferred but not always required. If your provider doesn’t specify timing, ask whether the specific tests they’ve ordered are time-sensitive.