Lab test glossary · Hormones
Testosterone: what it means
Also known as: total testosterone, free testosterone
Testosterone is the primary male sex hormone (also important in women); low levels can contribute to fatigue, low libido, and changes in mood and body composition.
What it measures
Testosterone drives male sexual development and also plays a role in muscle, bone, mood, and libido in everyone. Tests report total testosterone and sometimes free testosterone (the unbound, active portion). Levels swing through the day and are highest in the morning, so timing of the draw matters a lot.
Typical range
Ranges vary widely by age, sex, and assay. Adult men are often roughly 300–1,000 ng/dL total, but 'low' is defined together with symptoms and usually confirmed on a repeat morning test.
Reference ranges differ between labs and are printed on your own report — always read your result against that range, not a general one.
What a high result can mean
- Testosterone supplementation or replacement therapy
- Certain adrenal or testicular conditions
A high value is a starting point for a conversation, not a diagnosis — many causes are benign or temporary.
What a low result can mean
- Aging, obesity, or poor sleep
- Pituitary or testicular problems
- Some medications and chronic illness
Why the trend matters
Because testosterone fluctuates hour to hour and day to day, a morning-drawn trend is far more reliable than any single number.
When to talk to your doctor
Symptoms of low testosterone plus a low morning level are worth discussing with your doctor, who will usually confirm before acting.
Frequently asked questions
What is a normal testosterone level?
Ranges vary widely by age, sex, and assay; adult men are often roughly 300–1,000 ng/dL total, but 'low' is defined together with symptoms and usually confirmed on a repeat morning test.
What are the symptoms of low testosterone?
Low libido, fatigue, low mood, and changes in muscle or body composition can accompany low testosterone — but these are nonspecific, so they're interpreted alongside a properly-timed blood level.
Why should testosterone be tested in the morning?
Testosterone follows a daily rhythm and peaks in the morning, so a morning draw gives the most reliable and comparable result.
This page is general education about a common lab test — it isn’t medical advice and can’t interpret your specific result. What a value means depends on your history, symptoms, and the rest of your labs, which is a conversation for you and your clinician.