Testosterone, decoded.

The editorial TLDR.

What testosterone actually is.

Testosterone is an androgen — a class of steroid hormones produced in both sexes, just in very different amounts. In women, roughly 25% of circulating testosterone comes directly from the ovaries, 25% from the adrenal glands, and the remaining 50% from peripheral conversion of precursor hormones (chiefly DHEA and androstenedione) in fat, skin and other tissues. That distribution matters: it means a woman's testosterone reflects ovarian, adrenal and metabolic health all at once.

Like other steroid hormones, most testosterone in the bloodstream travels bound to carrier proteins — primarily sex hormone binding globulin (SHBG) and, more loosely, albumin. Only the small unbound fraction — the "free" testosterone — can leave the bloodstream and act on cells. That's why two women with identical total testosterone numbers can feel very differently in their bodies if their SHBG levels diverge. A high SHBG ties up more testosterone; a low SHBG releases more free hormone into circulation.

"Total testosterone tells you how much is in the bloodstream. Free testosterone tells you how much is actually available to act."

Testosterone is then converted, in tissues that need it, into either dihydrotestosterone (DHT — more potent, drives androgenic effects on skin and hair) or estradiol (via the enzyme aromatase, in fat tissue and elsewhere). This is why the same testosterone molecule can show up clinically as anything from acne and unwanted hair growth, to mood stability, to bone density support — depending on what the body does with it downstream.

U.S. labs typically measure testosterone in one of two ways. Standard immunoassays are fast and inexpensive but can be unreliable at the low end of the female range — which is exactly where most women's results sit. Liquid chromatography–mass spectrometry (LC-MS/MS) is the more accurate gold-standard method, and is the one most endocrinologists prefer when the result actually matters clinically. It's worth asking which assay your lab uses.

Why testosterone matters for women.

The narrative most women have absorbed is that testosterone is the hormone men have and estrogen is the hormone women have. That framing is wrong in both directions — and clinically, it means a lot of women's symptoms get filed under estrogen or "stress" when testosterone is part of the picture.

PCOS and androgen excess in the reproductive years. Polycystic ovary syndrome affects an estimated one in ten U.S. women of reproductive age. Elevated total or free testosterone — often paired with elevated DHEA-S, low SHBG, and elevated fasting insulin — is one of the lab signatures clinicians look for. Symptomatically: irregular or absent cycles, acne along the jawline, hair thinning at the crown, hair growth on the chin or upper lip, and difficulty losing weight. None of these is diagnostic on its own; PCOS is a clinical diagnosis that uses labs as one input.

Low libido, mood and motivation across decades. Multiple studies — including those informing the Global Consensus Position Statement on the use of testosterone therapy for women — suggest that low testosterone in women is associated with reduced libido, lower mood, less motivation, and reduced sense of well-being. The evidence is strongest for hypoactive sexual desire disorder in postmenopausal women, where careful testosterone replacement is now an internationally accepted clinical option. The conversation in the U.S. is still catching up; many primary-care providers will not have raised it.

Perimenopause and menopause. Ovarian testosterone production declines gradually from the late thirties onward — not as sharply as estrogen, but meaningfully. By the time many women reach the menopause transition, their testosterone is roughly half its peak reproductive-age value. The libido, motivation and energy changes that show up in the late forties and fifties are not only an estrogen story; they are often a testosterone story too.

Bone density and lean mass. Androgens support bone formation and lean muscle maintenance. The relationship between testosterone and bone mineral density in women is less direct than estrogen's, but persistently very low testosterone alongside low estradiol can compound risk over time.

Hormonal contraception and SHBG. Combined oral contraception raises SHBG, sometimes substantially — which means even a "normal" total testosterone may translate into a much lower free testosterone. Many women report libido and mood shifts on the pill that resolve months after stopping; a measured SHBG and free testosterone is one way to make sense of the pattern.

What the ranges generally mean.

U.S. labs typically report total testosterone in nanograms per deciliter (ng/dL) and free testosterone in picograms per milliliter (pg/mL). Reference bands vary by laboratory and by assay; the broad shapes below are common for non-pregnant adult women.

Illustrative ranges, not diagnostic. Reference ranges vary by laboratory, assay, age, cycle phase and menopausal status. Always discuss your specific result with a qualified healthcare provider.

What may drive testosterone low or high.

The patterns below come up most often when total or free testosterone reads outside the comfortable zone in U.S. women.

What may drive testosterone low.

• Perimenopause and menopause. Ovarian production declines gradually through the late thirties and forties. By the menopause transition, total testosterone is often roughly half its peak.
• Surgical menopause (oophorectomy). Removal of one or both ovaries can drop testosterone abruptly. Many women report libido and mood changes that resolve only when this is addressed clinically.
• Combined oral contraception. Estrogen-containing contraception raises SHBG, which lowers free testosterone. Some women feel this; many don't.
• Chronic stress and HPA axis suppression. Sustained high cortisol can suppress adrenal androgen production over time.
• Pituitary or hypothalamic patterns. Less common but worth ruling out — particularly with very low testosterone, low estradiol, and absent or irregular cycles.
• Adrenal insufficiency. The adrenal glands produce a meaningful share of female testosterone via DHEA precursors. Adrenal under-function shows up in testosterone too.

What may drive testosterone elevated.

• Polycystic ovary syndrome (PCOS). The most common cause of mildly elevated testosterone in U.S. women of reproductive age. Often paired with low SHBG, elevated DHEA-S and elevated fasting insulin.
• Congenital adrenal hyperplasia (non-classic). A less common but clinically important cause of androgen excess. Typically distinguished with a 17-hydroxyprogesterone test.
• Insulin resistance. High insulin drives ovarian androgen production and lowers SHBG, both of which raise free testosterone. The metabolic and reproductive systems are tightly linked.
• Cushing's syndrome. Excess cortisol patterns can co-occur with androgen excess.
• Androgen-secreting tumors. Rare, but worth ruling out with very high or rapidly rising testosterone, particularly with rapid-onset virilization symptoms.
• Exogenous androgens. Some over-the-counter and compounded testosterone products — sometimes used off-label for libido or athletic performance — can push levels well above the female reference range.

Your provider will guide the conversation based on your full medical context. The point of these questions is to make sure the testosterone conversation actually happens — and that the numbers get read together rather than in isolation.

When to test, and how it's measured.

The testosterone test is a standard venous blood draw, typically bundled with SHBG and (often) DHEA-S, free testosterone and estradiol. No fasting is required for testosterone itself, though many women's-health panels pair it with markers that do require fasting (insulin, lipids).

Timing matters in two ways. First, time of day: testosterone peaks in the early morning and falls through the day. A morning draw, ideally before 10 a.m., gives the most interpretable number. Second, cycle day: testosterone shifts modestly across the cycle, with a mild peak around ovulation, but the swing is smaller than estradiol or progesterone. A cycle-day-3 draw is conventional if estradiol and FSH are being measured in the same panel; otherwise, day of cycle matters less for testosterone in isolation.

If you're on combined oral contraception or hormonal therapy, mention it on the requisition — both can shift SHBG and therefore free testosterone. Biotin supplementation can also interfere with some immunoassays; the conventional advice is to pause biotin for at least 48 hours before any hormonal panel.

Direct-to-consumer at-home tests — Function Health, LetsGetChecked, Quest Direct and others — include testosterone in most of their comprehensive women's panels. They're useful for a baseline; they don't replace the conversation about what to do with the result. For the trade-offs across services, see our guide to at-home blood tests for women.

Related biomarkers worth understanding.

Testosterone rarely sits alone in a thoughtful workup. The markers below come up most often alongside it.

• SHBG — sex hormone binding globulin. Determines how much testosterone is free versus bound. The single most useful number to read alongside testosterone.
• DHEA-S — the main adrenal androgen precursor. Helps distinguish ovarian from adrenal contributions to elevated androgens.
• Estradiol — testosterone aromatizes into estradiol in fat tissue and elsewhere. The two move together in many clinical patterns.
• Fasting insulin — insulin resistance is one of the most common drivers of elevated free testosterone in U.S. women. Worth pairing.
• Cortisol — chronic stress patterns can suppress adrenal androgen output and reshape the testosterone landscape.
• Progesterone — the third leg of the reproductive-hormone read. Often informative alongside testosterone in cycle workups.