Total testosterone ng/dL to nmol/L Converter

Testosterone in two units: the short answer

To convert total testosterone from ng/dL to nmol/L, multiply by 0.0347 (or divide by 28.84). To convert nmol/L back to ng/dL, multiply by 28.84. A level of 300 ng/dL is therefore about 10.4 nmol/L, and 12 nmol/L is about 346 ng/dL. The converter above handles both directions and shows how a value compares with the harmonized adult male reference range.

Testosterone results are especially hard to compare across borders because the numbers differ so much between units – a healthy man might read "550" in the United States and "19" in the UK for the same blood level. Treatment decisions also hinge on thresholds that guidelines express in one unit or the other, so a correct conversion matters. This guide covers how the test works, the conversion, normal ranges for men and women, the many factors that change a result, and when a result needs medical attention.

What a total testosterone test measures

Testosterone is the main androgen (male sex hormone). In men it is made mostly by the testes, in women by the ovaries and adrenal glands in much smaller quantities. In the blood it circulates in three forms:

• Bound tightly to sex hormone-binding globulin (SHBG) – roughly 40–60% in men. This fraction is not readily available to tissues.
• Bound loosely to albumin – roughly 40–50%. It can detach easily, so it is partly available.
• Free (unbound) – only about 1–3%. This is the biologically active fraction.

A total testosterone test measures all three together. It is the first-line test in almost every guideline. When SHBG is unusually high or low – for example with obesity, ageing, liver disease or thyroid disorders – total testosterone can be misleading, and clinicians may also measure SHBG and calculate or measure free testosterone. Free testosterone uses different units (pg/mL or pmol/L, sometimes ng/dL) and has its own converter on this site.

How the test is performed

Most laboratories use automated immunoassays. These are reliable in the normal male range but can be inaccurate at the low concentrations found in women and children, where liquid chromatography–tandem mass spectrometry (LC-MS/MS) is preferred. The US CDC runs a Hormone Standardization Program to bring assays into line with a reference method, which has reduced – but not eliminated – differences between laboratories.

ng/dL and nmol/L explained

ng/dL (nanograms per deciliter) is a mass concentration used in the United States and some other countries. Some laboratories report in ng/mL, which is 100 times smaller numerically: 5.0 ng/mL equals 500 ng/dL. Always check whether the "d" is there.

nmol/L (nanomoles per liter) is the SI unit, used in the UK, Europe, Australia, Canada and elsewhere.

Why the factor is 0.0347

Testosterone has a molar mass of 288.4 g/mol. One nanomole therefore weighs 288.4 ng. A concentration of 1 ng/dL is 10 ng per liter, which is 10 ÷ 288.4 = 0.03467 nmol/L. The reverse factor is 288.4 ÷ 10 = 28.84.

How to convert testosterone step by step

1. Confirm the unit: ng/dL, ng/mL or nmol/L.
2. If the result is in ng/mL, multiply by 100 to get ng/dL first.
3. From ng/dL, multiply by 0.0347 to get nmol/L.
4. From nmol/L, multiply by 28.84 to get ng/dL.
5. Round nmol/L to one decimal place and ng/dL to the nearest whole number.

Worked examples

• 264 ng/dL × 0.0347 = 9.2 nmol/L – the lower limit of the harmonized range for men aged 19–39.
• 300 ng/dL × 0.0347 = 10.4 nmol/L – the threshold used in the American Urological Association guideline.
• 916 ng/dL × 0.0347 = 31.8 nmol/L – the upper limit of the harmonized range.
• 8 nmol/L × 28.84 = 231 ng/dL.
• 12 nmol/L × 28.84 = 346 ng/dL – the level below which European guidance considers testosterone deficiency possible.
• 1.8 nmol/L × 28.84 = 52 ng/dL – within the typical range for women.
• 4.5 ng/mL = 450 ng/dL × 0.0347 = 15.6 nmol/L.

Mental shortcut

Divide ng/dL by 30 for a quick nmol/L estimate (slightly low), or multiply nmol/L by 29. For 600 ng/dL: 600 ÷ 30 = 20, versus the exact 20.8 nmol/L.

Testosterone conversion chart

Normal testosterone ranges

Men

In 2017, a study using CDC-standardized LC-MS/MS measurements in four large cohorts defined a harmonized reference range for healthy, non-obese men aged 19–39 of 264–916 ng/dL (9.2–31.8 nmol/L). Many US laboratories have adopted this range or something close to it. Older laboratory ranges, often starting around 250–300 ng/dL, are still in use, so your report's own range is the most relevant one.

Clinical thresholds for diagnosing low testosterone (male hypogonadism) differ slightly between guidelines:

• The American Urological Association (AUA) uses a total testosterone below 300 ng/dL (10.4 nmol/L) on two separate early-morning measurements, together with symptoms.
• The Endocrine Society recommends diagnosing hypogonadism only in men with consistent symptoms and unequivocally and consistently low morning levels, using the laboratory's harmonized lower limit (about 264 ng/dL, 9.2 nmol/L).
• The European Association of Urology suggests that a total testosterone below about 12 nmol/L (346 ng/dL) with symptoms may justify further assessment, and levels below 8 nmol/L (231 ng/dL) more clearly indicate deficiency.

Testosterone levels in men fall slowly with age – on average around 1% per year after 40 – but much of the drop seen in older men is linked to obesity and illness rather than age itself.

Women

Typical ranges for adult women are roughly 15–70 ng/dL (0.5–2.4 nmol/L), although laboratories vary considerably, and immunoassays are less accurate at these levels. Testosterone is lower after menopause, mostly because ovarian and adrenal production fall. In women, testosterone is mainly measured when there are signs of androgen excess – excess hair growth, acne, irregular periods – which most often point to polycystic ovary syndrome (PCOS). A level above about 150–200 ng/dL (5.2–6.9 nmol/L) in a woman is uncommon even in PCOS and should prompt a search for an androgen-secreting tumour or other cause.

Children and adolescents

Before puberty, levels are very low (usually below 20 ng/dL, 0.7 nmol/L) in both sexes. In boys, levels rise steeply through puberty to adult values by about age 17. Paediatric results should always be interpreted against age- and puberty-specific ranges from the laboratory.

Symptoms of low testosterone

Low testosterone causes symptoms that overlap with many other conditions, which is why guidelines require both symptoms and confirmed low levels before diagnosis. The symptoms most specific to testosterone deficiency in men are:

• reduced sexual desire and activity
• fewer spontaneous or morning erections, and erectile dysfunction
• breast discomfort or enlargement (gynecomastia)
• loss of body hair and reduced need to shave
• very small or shrinking testes
• low-trauma fractures or reduced bone density
• hot flushes and sweats with very low levels

Less specific symptoms include fatigue, low mood, poor concentration, reduced muscle strength and increased body fat. These are common and have many causes, so on their own they are not enough to diagnose testosterone deficiency.

Primary and secondary hypogonadism

When a low testosterone result is confirmed, the next step is usually to measure luteinizing hormone (LH) and follicle-stimulating hormone (FSH), which are released by the pituitary gland and stimulate the testes.

• Primary hypogonadism (testicular failure): testosterone is low and LH and FSH are high, because the pituitary is pushing hard on testes that cannot respond. Causes include Klinefelter syndrome, previous mumps orchitis, testicular injury, chemotherapy or radiotherapy.
• Secondary hypogonadism (pituitary or hypothalamic): testosterone is low with low or inappropriately normal LH and FSH. Causes include obesity, opioid or steroid use, high prolactin, pituitary tumours, severe illness and iron overload. Some causes, such as obesity and opioid use, are reversible.

This distinction matters because it changes the further tests (for example prolactin, iron studies or pituitary MRI) and the treatment options, especially for men who wish to preserve fertility – testosterone therapy suppresses sperm production.

Testosterone and polycystic ovary syndrome

In women, the most common reason for a raised testosterone is PCOS. Under the international evidence-based PCOS guideline, biochemical androgen excess is one of the diagnostic features, and calculated free testosterone or the free androgen index is preferred over total testosterone because it is more sensitive. Total testosterone in PCOS is usually only mildly raised – often in the range of about 50–150 ng/dL (1.7–5.2 nmol/L). Hormonal contraceptives raise SHBG and lower testosterone, so results taken on the pill may hide androgen excess.

What affects testosterone results

• Time of day. Testosterone peaks in the early morning and can be 20–30% lower by late afternoon in younger men. Guidelines recommend testing between about 7 and 10 a.m. (or within three hours of waking for shift workers).
• Food. Eating, particularly a glucose load, can temporarily lower testosterone. A fasting morning sample is preferred.
• Acute illness, sleep deprivation and intense training all lower levels temporarily. Testing should be delayed until recovery.
• Obesity lowers SHBG and total testosterone; weight loss often raises it.
• Medicines – opioids, glucocorticoids, anabolic steroids (after stopping), and drugs that reduce testosterone production all lower levels. Testosterone therapy itself raises them, and the timing of the sample relative to the dose matters.
• SHBG changes – raised by ageing, hyperthyroidism, liver disease and some anticonvulsants; lowered by obesity, type 2 diabetes, hypothyroidism and nephrotic syndrome.
• Biotin supplements can interfere with some immunoassays. Stop high-dose biotin for at least 48–72 hours before testing unless your doctor says otherwise.

Because of this variability, no guideline diagnoses low testosterone from a single result: a low value should be confirmed with a repeat fasting morning sample.

Monitoring testosterone therapy

For men on testosterone treatment, guidelines usually aim for levels in the mid-normal range – roughly 400–700 ng/dL (14–24 nmol/L), measured at a point that depends on the preparation (for example, midway between injections, or several hours after applying a gel). Hematocrit and, in older men, prostate markers are monitored alongside testosterone.

Comparing results from different laboratories

If you have results from two laboratories – for example one in the US and one in Europe – convert them into the same unit before deciding whether your level has changed. Then consider three further points:

1. Method. A result from an immunoassay and one from LC-MS/MS may differ by 10–20% at normal male levels and by much more at female levels. Many reports state the method in small print.
2. Reference range. A laboratory still using an older range (for example 300–1,000 ng/dL) and one using the harmonized range (264–916 ng/dL) may flag the same number differently. The range belongs to the laboratory, not to the unit.
3. Sample conditions. A fasting 8 a.m. sample and a non-fasting 4 p.m. sample are not comparable even in the same laboratory.

A practical example: a man has 11.0 nmol/L from a UK laboratory in the afternoon and 410 ng/dL from a US laboratory in the morning. Converted, these are 317 ng/dL and 14.2 nmol/L. The apparent "rise" of almost 30% is mostly explained by the time of day, not by a real change.

When to see a doctor

See a doctor if you are a man with symptoms such as reduced sexual desire, erectile problems, loss of morning erections, low energy, loss of muscle or breast enlargement, especially if a morning testosterone is below about 300 ng/dL (10.4 nmol/L). Very low levels, under about 150 ng/dL (5.2 nmol/L), merit investigation of the pituitary gland. Women with rapidly worsening excess hair, a deepening voice or levels well above the female range need prompt assessment. Anyone using non-prescribed testosterone or anabolic steroids should discuss blood monitoring with a clinician.