What the value means
Testosterone is reported in nmol/L and fluctuates during the day – it is usually highest in the morning. Laboratories use different ranges for men, often roughly 8–30 nmol/L, and include older men in them, so a value “just within normal” may not be optimal for a 30-year-old. What matters is how the result fits with symptoms such as fatigue, lower libido or muscle loss. In women the values are much lower and are assessed differently.
Possible causes
- Timing of the draw – an afternoon draw, testing after a night shift or during illness can push the value down.
- Sleep – persistently short sleep or untreated sleep apnoea demonstrably lower testosterone.
- Excess weight and insulin resistance – visceral fat and high insulin are among the most common causes of low testosterone in young men.
- Energy deficit and overtraining – strict diets, very low body fat and heavy training without recovery suppress hormone production.
- Medication and substances – opioids, some psychiatric drugs, alcohol and especially past anabolic steroid use can suppress production for a long time.
- Medical conditions – disorders of the testes or pituitary, high prolactin or iron overload need to be ruled out by a doctor.
What you can do
- Repeat the test – in the morning between 7 and 10 a.m., fasting, after a good night’s sleep; add SHBG, free testosterone, LH, FSH and prolactin.
- Sleep 7–9 hours – keep a regular schedule; if you snore and feel sleepy during the day, consider a sleep assessment.
- Strength training and movement – two to three strength sessions a week and daily walking support insulin sensitivity and hormones.
- Body weight – in people with excess weight, even modest weight loss usually raises testosterone.
- Diet and alcohol – enough protein, zinc and vitamin D from food, less alcohol; “testosterone booster” supplements mostly have weak evidence.
When to see a doctor
See a doctor (GP, endocrinologist or urologist) if the low value is confirmed on repeat testing, or if you have marked symptoms, fertility problems, shrinking testes or breast enlargement. Do not take testosterone or other hormones on your own – they can suppress fertility. Do not stop any medication you take without talking to your doctor.