Testosterone: what it is, what it tells you and when it’s tested

Testosterone is the main male hormone. In men the testicles make it; in women the ovaries and adrenal glands make much smaller amounts. It matters for sex drive, muscle, bone and energy.

When it’s tested

In men, doctors order it when there are symptoms: lower sex drive, erection problems, tiredness that does not go away, less strength. In women, they mostly order it for excess hair, acne or irregular periods.

It is not a routine test for people who feel well. One result alone is not enough for a diagnosis: it takes symptoms and, if it is low, a second morning test.

That is why Rosa does not test it. Instead it looks at things that often go hand in hand with low testosterone: blood sugar, HbA1c and insulin.

What it tells you, and what it does not

Total testosterone is all of it in your blood. Nearly all of it is bound to blood proteins, mainly SHBG, and so does not act. The part that works is free testosterone.

So a normal total with a high SHBG can hide too little free testosterone. And a low total with a low SHBG is sometimes not a real problem.

A low result does not tell you why on its own. To see whether the problem is in the testicles or the pituitary gland, your doctor looks at other hormones too.

That is why it is read together with other tests:

• SHBG: It is used to work out free testosterone
• LH: It shows whether the problem is in the testicles or the pituitary
• Prolactin: If it is high, it can lower testosterone
• HbA1c: Diabetes often lowers testosterone

Normal testosterone levels

The lab decides what is normal, and it is very different for men and women. In women the levels are much lower. Your report may use ng/mL, nmol/L or ng/dL: always check the unit before comparing numbers.

In men, Italian guidelines call a total testosterone of 12 nmol/L or less low, about 3.5 ng/mL. For calculated free testosterone, below 220 pmol/L.

Testosterone is highest in the morning and falls during the day. The test is done before 10 am, fasting. If it is low, it is repeated on another day before anyone talks about a diagnosis.

If your testosterone is low or high

• Low testosterone: In men, weight, diabetes, sleep or medicines are often behind it. It needs a second test to confirm it.
• High testosterone: In women the most common cause is polycystic ovary syndrome. In men it often comes from testosterone or steroids taken from outside. Talk to your doctor.

What can skew the result

Testosterone changes a lot with the time of day and your health. It helps to know this before your blood test.

• The time of the test: It is higher in the morning. An afternoon test can give a low result even when all is well.
• Eating: A meal before the test can lower it a little. That is why it is done fasting.
• A recent illness: Fever, flu or a hospital stay lowers it for a while. It is best measured when you are well.
• Medicines and hormones: Opioids, high-dose steroids such as prednisone, anabolic steroids and the pill change the result. Tell your doctor, and do not stop them on your own.

When to worry

Talk to your doctor if:

• You are a man with lower sex drive, erection problems or fewer morning erections.
• Your testosterone is low on two morning tests.
• You are a woman with excess hair, acne or irregular periods.
• You are a woman and the symptoms came on fast, over a few months, with a deeper voice or hair loss: see your doctor soon.
• You have headaches that do not go away or changes in your vision: see your doctor soon.

Frequently asked questions

What are normal testosterone levels in men? It depends on the lab and the unit. Italian guidelines call a total of 12 nmol/L or less low, about 3.5 ng/mL, confirmed on two morning tests.

What is the difference between total and free testosterone? Total is all of it in your blood. Free is the small part not bound to proteins, the part that acts. Your doctor works it out from the total and SHBG.

What time should a testosterone test be done? In the morning, before 10 am, and fasting. Later in the day the level falls.

Should women have their testosterone tested? It is tested when there are signs of too many androgens, such as excess hair, acne or irregular periods. Mostly it helps find out whether there is polycystic ovary syndrome.

Does Rosa test testosterone? No. Rosa measures blood sugar, HbA1c and insulin, which say a lot about the metabolism linked to testosterone. If your doctor wants testosterone, they order it separately.

Sources

• Isidori and colleagues, adult and late-onset male hypogonadism: the clinical practice guidelines of the Italian Society of Andrology and Sexual Medicine (SIAMS) and the Italian Society of Endocrinology (SIE). Journal of Endocrinological Investigation, 2022. PMID 36018454
• Bhasin and colleagues, testosterone therapy in men with hypogonadism: an Endocrine Society clinical practice guideline. Journal of Clinical Endocrinology and Metabolism, 2018. PMID 29562364
• Teede and colleagues, recommendations from the 2023 international evidence-based guideline for the assessment and management of polycystic ovary syndrome. Journal of Clinical Endocrinology and Metabolism, 2023. PMID 37580314