Total Testosterone

If you're a man with a fading sex drive, flat energy, or muscle that won't come back, total testosterone is the number that tells you whether low hormones could be part of the story. If you're a woman with irregular periods, acne, or hair growing where you don't want it, it's one of the first checks for too much male hormone. In both cases it's a routine blood test you can order yourself.

In large studies, men with low testosterone have weaker bones, less muscle, and higher death rates, though researchers still disagree about how much of that the hormone itself causes. The way it's measured also matters. This version of the test uses an immunoassay, which reads adult male levels reasonably well but gets less accurate at the low levels found in women, children, and some men who are seriously ill.

What the Number Includes

Testosterone is a steroid hormone your body builds from cholesterol. In men it comes mostly from the testes, which make it in response to a pituitary signal called luteinizing hormone (LH), with a small amount from the adrenal glands. In women it comes from direct ovarian and adrenal production plus conversion of precursor hormones in tissues such as fat and liver; many reviews estimate that conversion supplies about half and the rest is split between the ovaries and adrenal glands.

Very little floats freely in the blood. About 43% to 45% is held tightly by sex hormone-binding globulin (SHBG). About 50% to 55% is held loosely by albumin. Albumin is the most common protein in blood. Only 1% to 4% is free. The free and loosely held portions are the ones your tissues can use.

A total testosterone test adds all three portions together, so anything that changes SHBG changes the total even if the usable amount stays the same. Obesity and insulin resistance lower SHBG, which means the total can look low while free testosterone is normal. In many older men SHBG goes up, so a total inside the expected range can hide a free level that's too low.

How Well the Immunoassay Reads Your Level

An immunoassay uses antibodies that latch onto testosterone, along with a labeled tracer that competes for the same antibodies, and the analyzer turns the tracer's signal into a concentration. For adult men it does a reasonable job. In a study of 3,174 European men, an automated immunoassay caught 75 of every 100 men whose level was low by mass spectrometry, the more precise reference method, and correctly cleared about 96 of every 100 men whose level was not low. In another comparison, more than 60% of automated results in adult men came within 20% of the mass spectrometry value.

Different analyzers often disagree. On samples from the same men, some platforms read about 90 ng/dL low on average and others read nearly 100 ng/dL high, and one research cohort saw reported values jump 11% when it switched manufacturers. A European survey found wide variation in the lab cutoffs used for men, and fewer than half of labs required fasting morning samples.

Accuracy falls off most in people with low levels or unusual blood chemistry. When ten immunoassays were checked against mass spectrometry, none was reliable enough for the very low concentrations found in children and women. The three groups below show how large the errors can get.

Sources: Martínez-Escribano et al.; Jansen et al.; Ankarberg-Lindgren et al.

What this means for you: if you're an adult man without obesity or kidney failure, an immunoassay result is a reasonable first check. If you're a woman, carry a lot of extra weight, are on dialysis, or are on hormone-blocking treatment for prostate cancer, where immunoassays also fall short near the treatment goal, treat the result as a screen. Confirm it with SHBG and free testosterone, or with a mass spectrometry test.

Low Testosterone in Men

Doctors call low testosterone plus matching symptoms male hypogonadism. The usual symptoms are low libido, erectile problems, loss of muscle, anemia, and thinning bones. In a Swedish cohort of 657 men, lower total testosterone went with a heavier burden of sexual symptoms, and that held whichever lab method was used.

Neither the symptoms nor the number settles the question alone. The symptoms have many possible causes, and a single reading varies enough that it can mislead you. A diagnosis needs both pieces to agree, which is why a borderline result calls for a second test and a few follow-up tests rather than a prescription.

Mortality and Heart Disease

Large cohort studies keep finding that men with lower testosterone die sooner. In about 149,000 middle-aged and older UK men, lower testosterone went with higher death rates from all causes and from cancer. In the EPIC-Norfolk study in England, men with higher testosterone had lower death rates from heart disease and from all causes. A German cohort of 1,954 men aged 20 to 79 found that low testosterone predicted more deaths, including from heart disease and cancer, and a California study of 794 older men followed for about 20 years found the same even after accounting for standard risk factors and existing illness.

Studies that pool many cohorts are less consistent. A 2024 analysis that combined individual data from many cohorts found higher all-cause mortality in men with low testosterone, and a 2018 meta-analysis concluded low testosterone marks higher cardiovascular risk. A 2021 meta-analysis of community-dwelling men found no significant link with heart disease deaths or overall deaths, and a 2010 analysis found no link in middle-aged men. These cohorts used a mix of lab methods, so their findings tell you which direction risk runs, and their absolute numbers don't carry over to your immunoassay result.

Two more findings help explain the disagreement. In 5,786 middle-aged and older Chinese men, both low and high testosterone went with greater cardiovascular risk, and low testosterone tracked with high blood pressure. A genetic study of 625,650 people couldn't show that testosterone itself causes most of the diseases it's linked to, apart from sex-specific conditions. Taken together, these suggest low testosterone works mainly as a sign of overall health. Obesity, chronic illness, and other problems push it down, so a low number in observational data partly reflects whatever else is going wrong. That's why cohorts link it to earlier death while pooled and genetic analyses can't pin down that the hormone is the cause.

In practice, if your result is low, look for the reason behind it. Check your weight, blood sugar, kidney function, and medications before you assume the testes are the problem, and before you conclude that raising the number will lower your risk.

Diabetes, Kidney Disease, and Metabolic Health

British sexual medicine guidelines link testosterone deficiency in men with higher rates of type 2 diabetes and chronic kidney disease. Testosterone falls as kidney disease gets more advanced. In 2,419 men with moderate to advanced kidney disease, those with low total testosterone had higher mortality. Genetic evidence suggests the link with diabetes probably runs from poor metabolic health to low testosterone more than the other way around.

Because of these links, the American Urological Association recommends checking testosterone in men with type 2 diabetes, unexplained bone loss, chronic opioid use, past radiation to the testes, or pituitary disease. If you have diabetes or obesity, remember that your SHBG is probably low too. Order SHBG and free testosterone along with the total, because the total alone may overstate how low you are.

Androgen Excess in Women

Testosterone matters in women for reproduction, bone, muscle, heart health, and brain function, though there isn't one agreed standard range for women. High testosterone is one lab sign used in polycystic ovary syndrome (PCOS), along with symptoms and ovulation pattern. PCOS is a common hormone condition that causes irregular ovulation, excess hair, acne, and fertility problems. Very high levels can point to an androgen-secreting tumor of the ovary or adrenal gland, and immunoassays usually pick up those larger elevations.

For diagnosing PCOS, total testosterone caught about 74 of every 100 women who had it and correctly cleared about 86 of every 100 who didn't, across 23 studies. Direct immunoassays tend to overread women's low levels and vary enough that mass spectrometry is preferred when the result will guide a diagnosis or treatment. In 906 infertile women with PCOS, mass spectrometry did a better job identifying the women at real risk of poor fertility outcomes. If your immunoassay result comes back high, confirm it with mass spectrometry before you act on it.

Why a Single Reading Can Fool You

Testosterone follows a daily rhythm, responds to meals and illness, and depends on SHBG, so when and how your blood is drawn changes the result. These are the most common ways a single reading ends up misleading:

• Time of day and food: levels peak in the early morning and fall through the afternoon, with larger percentage swings in younger men and smaller swings with age. Glucose and food also lower testosterone, so an afternoon or after-breakfast draw can read low.
• Recent illness or surgery: acute medical illness can push testosterone down in up to 62% of patients, and surgery or a hospital stay can do the same. Wait until you've fully recovered before testing.
• A hard workout: moderate or intense exercise raises testosterone for a short time, and across 48 studies the rise was gone within about 30 minutes. Don't train right before your draw.
• Unusual binding proteins or blood chemistry: obesity, aging, HIV, and kidney failure change SHBG or the makeup of the blood, so the total can be misleading. In men with HIV, the total missed more than 70% of true deficiency.
• Look-alike hormones at low levels: the antibodies in an immunoassay can also pick up other steroids that resemble testosterone. This matters most when the true level is low, as in women, children, and men on hormone-blocking treatment.

Some medications change the number without meaning your testes are failing:

• Glucocorticoids (prednisone-type steroids): high cortisol levels suppress testosterone output from the testes within hours, so a reading taken during a course of these drugs doesn't show your usual baseline.
• Metformin: in a one-month randomized trial in 70 newly diagnosed men with type 2 diabetes, metformin lowered total testosterone by about 66 ng/dL regardless of how well blood sugar was controlled. Keep this in mind before you read a lower result after starting metformin as a new problem.
• Statins: men taking statins have had lower testosterone in observational studies. Those studies can't prove the drug is the cause, so treat this as context for a borderline result, not a reason to stop a heart-protective medicine.
• High-dose biotin: many automated immunoassays rely on a biotin-based chemistry, and biotin supplements can throw the result off in either direction. Pause high-dose biotin before your draw.

Tracking Your Trend

Testosterone varies a lot within the same person. In healthy men, day-to-day variation runs about 16% to 18.7%. In a group of 121 men sampled within four hours of waking, a man's true average could plausibly fall anywhere from 65% to 153% of any single reading.

That variation has real consequences. Up to half of men labeled low on a first test come back normal on the next one. In the 121-man group, only 40% of men whose first result was clearly low stayed in that category averaged over six visits, and 20% averaged out of the low range. For a change between two morning draws to mean more than normal fluctuation, it has to be larger than about 52%.

So read one result as a starting point. Confirm any low reading with a second fasting draw between 7 and 10 a.m. Get a baseline, retest in 3 to 6 months if you're losing weight, changing medications, or starting treatment, and then test at least once a year. Use the same lab each time, since a change of analyzer alone can shift the number by 11%.

If you're on testosterone therapy, time your draws relative to your dose. With a daily gel, 70% of men had adequate levels 2 hours after applying it but only 36.7% at 23 hours, so draw at the same point in your dosing cycle every time.

What to Do With an Unexpected Result

Once a second morning draw has confirmed the result, the next step depends on the pattern:

• Low total in a man: add SHBG, free testosterone, LH, and follicle-stimulating hormone (FSH). FSH is another pituitary signal, and it helps drive sperm production. Get free testosterone by equilibrium dialysis or calculated from total testosterone, SHBG, and albumin, because direct analog free testosterone kits are unreliable. Total testosterone also flags some men wrongly: in 3,672 men, a common low cutoff caught 91 of every 100 men whose calculated free testosterone was low, but it also flagged about a quarter of men whose free level was fine.
• Low total with high LH: the testes themselves aren't responding to the signal, which is called primary hypogonadism. A urologist or endocrinologist can work out the cause.
• Low total with low or normal LH: the problem probably starts in the pituitary or brain. Check prolactin and see an endocrinologist, since pituitary disease is one of the causes worth ruling out.
• Low total, low SHBG, normal free testosterone, and extra weight: this is the obesity pattern, and significant weight loss usually reverses it. If you're thinking about testosterone therapy and still want children, settle that question first, because guidelines advise against starting therapy if you're planning a family.
• High total in a woman: confirm it with mass spectrometry, then add SHBG, DHEA sulfate, LH, and FSH. DHEA sulfate is made by the adrenal glands and helps show whether they're the source. A very high or fast-rising level, especially with a deepening voice or other signs of masculinization, needs prompt imaging and an endocrinologist.