Testosterone: when low is low, and when a result is misleading

Why the first result is often wrong

Testosterone follows a daily rhythm, peaking in the early morning and falling through the day. It drops after a meal, during illness, after poor sleep and with alcohol. A sample taken at 15:00 after lunch will read low in many healthy men. Guidelines are clear: measure between 07:00 and 11:00, fasting, and repeat on a separate day before drawing any conclusion.

What else is measured

• SHBG (sex hormone-binding globulin), which binds most testosterone; the free fraction is what matters, and SHBG changes with age, weight and thyroid status
• LH and FSH, which show whether the signal from the pituitary is normal
• Prolactin, because a raised level can suppress testosterone and has its own causes
• Oestradiol, particularly in men carrying extra weight
• Full blood count, PSA, liver function and lipids as a baseline before any treatment is discussed

The symptoms that count

Low energy, low mood and low libido are common and non-specific. Loss of morning erections, reduced muscle mass despite training, increased body fat, and reduced shaving frequency are more suggestive. Treatment is considered when symptoms and repeated low results line up, not on a number alone.

Causes worth finding

Obesity, sleep apnoea, type 2 diabetes, some medications including opioids and anabolic steroid use, and pituitary conditions. Several of these are treatable without hormone replacement, and treating them may restore testosterone on its own.

If treatment is appropriate

Replacement is a long-term commitment with monitoring of blood count, PSA and symptoms. It is not a performance supplement, and it suppresses natural production and fertility, which matters for men who may want children.

In practice

A men's hormonal assessment at the clinic is done at the right time of day, repeated where needed, and reviewed with you in writing. See also Erectile dysfunction is often the first sign of something else.