Testosterone: symptoms, blood values and what affects your level

Testosterone drives your energy, libido, muscle and mood. From age 30 it drops by roughly 1 to 2 percent a year, but your lifestyle often weighs more than your age. Below you will read which symptoms matter, which blood values say something, and what really affects your level.

Honestly? Symptoms alone tell you little. Your blood values tell the story.

What is testosterone and what does it do?

Testosterone is your main androgenic hormone. It plays a role in libido, muscle mass, bone density, red blood cell production and mental drive. Men make it mostly in the testes, driven by LH and FSH from the pituitary. Women make smaller amounts in the ovaries and adrenal glands.

Most of your testosterone is bound to proteins and is not directly active. Only the free fraction can actually be used by your tissues. That is exactly why a single number can put you on the wrong track.

Your body keeps the hormone in a feedback loop. When testosterone drops, your pituitary sends more LH to push production. That loop explains why two men with the same total testosterone can still have very different stories.

What are the symptoms of low testosterone?

Low testosterone can show up as ongoing fatigue, lower sex drive, trouble building muscle, more belly fat, irritability and poor concentration. These complaints are not very specific. Sleep loss, stress, and a shortage of iron or vitamin D often produce the same picture.

That makes it hard to pin down low testosterone on feel alone. What you notice as an energy dip could just as easily come from your sleep.

In practice we see athletes notice it mostly in their recovery: sessions feel heavier, progress stalls and motivation sinks. To learn which complaints fit a low level and which values go with them, read low testosterone symptoms in men.

What affects your testosterone?

Your level depends on age, sleep, body fat, resistance training, alcohol and chronic stress. Sleep is the most underrated factor. One week of sleeping five hours a night lowered testosterone in young, healthy men by 10 to 15 percent (Leproult and Van Cauter, 2011).

A high body-fat percentage matters too. Fat tissue converts testosterone into estradiol through the enzyme aromatase, shifting the balance. Chronic stress keeps your cortisol high, and cortisol and testosterone often move in opposite directions.

The decline with age is real, but slow (Travison et al., 2007). For most men under fifty, sleep, training and body composition are the dials you can actually turn. How to do that without empty promises is covered in increasing testosterone naturally.

Which blood values say something about your testosterone?

One value is rarely enough. A solid hormone picture combines your total testosterone with the free fraction, the binding protein SHBG, the signalling hormone LH and estradiol. Together they show whether a low or high number actually carries clinical meaning.

This is the five-marker reading guide we give athletes:

• Total testosterone: your starting point, the sum of bound and free testosterone. A first impression, but it lacks context on its own.
• Free testosterone: the small, active fraction (roughly 1 to 3 percent). This is the form your tissues use, and often the value that explains complaints better.
• SHBG: the protein that binds testosterone. A high SHBG can make a normal total testosterone work out low for your body.
• LH: the signal from your pituitary. It helps tell whether low testosterone sits in the testes or in the signalling.
• Estradiol: a form of estrogen that men need too. Too much or too little can cause complaints, and it belongs in the assessment alongside the rest.

The deeper explanation of total versus free testosterone is in free testosterone and SHBG. To understand estradiol better, read estrogen in men.

How do you get your testosterone tested?

Testosterone is best measured in the morning, because your level peaks then and falls during the day. A single reading also says less than two readings on different days. A hormone panel measures several values at once, so you keep the context.

You can have your values measured with the General Hormones panel. If you already use testosterone therapy, the TRT Monitoring panel makes more sense. The practical side, from timing to preparation, is in how to test testosterone.

Keep reading in this series

This overview is your starting point. To go deeper on one part, these articles take it further:

• Increasing testosterone naturally: what sleep, training and body composition really do.
• Low testosterone in men: symptoms and the matching blood values.
• Testing testosterone: how, where and when.
• Free testosterone and SHBG: what your values really mean.
• Testosterone and muscle mass: the link with resistance training.
• Estrogen in men: the balance with testosterone.
• Understanding your testosterone values: how to read your numbers.
• TRT monitoring: which values you track during therapy.

My advice? Do not start with a supplement, start with a measurement. One morning draw with a full hormone panel gives you a baseline you can test every later choice against.

References

1. Travison TG, Araujo AB, O'Donnell AB, et al. A population-level decline in serum testosterone levels in American men. Journal of Clinical Endocrinology and Metabolism. 2007;92(1):196-202. PMID: 17062768.
2. Leproult R, Van Cauter E. Effect of 1 week of sleep restriction on testosterone levels in young healthy men. JAMA. 2011;305(21):2173-2174. PMID: 21632481.
3. Wu FCW, Tajar A, Beynon JM, et al. Identification of late-onset hypogonadism in middle-aged and elderly men. New England Journal of Medicine. 2010;363(2):123-135. PMID: 20554979.
4. Bhasin S, Brito JP, Cunningham GR, et al. Testosterone therapy in men with hypogonadism: an Endocrine Society clinical practice guideline. Journal of Clinical Endocrinology and Metabolism. 2018;103(5):1715-1744. PMID: 29562364.

Disclaimer

Every blood test result includes a professional assessment by a BIG-registered doctor. This article gives general information and is not a substitute for medical advice. A blood test is a tool to enter the conversation with your GP better informed, not a diagnosis in itself. For treatment decisions, discuss your results with your GP.