Before spending anything on a supplement, it is worth knowing whether you have a problem. That question has an answer, and it costs less than a month of most products in this category.
What to ask for
| Marker | What it tells you |
|---|---|
| Total testosterone | The headline figure, bound and unbound combined. The standard first-line test. |
| Free testosterone | The biologically active fraction, typically 1 to 3% of total. Can be low while total looks normal. |
| SHBG | The binding protein. Explains a mismatch between total and free. |
| LH and FSH | Pituitary signals. Distinguish a testicular problem from a pituitary one. |
Total testosterone alone is the most commonly ordered and the least informative in isolation. A man with elevated SHBG can present with a total figure in the middle of the reference range and a free fraction at the bottom of it.
Timing changes the result
Testosterone follows a circadian rhythm, peaking in the early morning and declining through the day. Clinical guidance is to sample in the morning, ideally before 10am, in a fasted state.1
Levels also vary between days in the same individual, which is why guidelines recommend confirming a low result with a second measurement on a separate morning before making any diagnosis. Acute illness, poor sleep the night before and recent intense exercise all move the number.
The single most common mistake
One afternoon test, taken after a bad night, interpreted as a diagnosis. It is not one. It is a data point with wide error bars.
Reading the number
Reference ranges vary between laboratories and assays, which is why comparing a result against a range you found online is unreliable. Broadly, the Endocrine Society considers a total testosterone consistently below roughly 300 ng/dL, combined with symptoms, as the threshold at which hypogonadism is considered.2
Two qualifications matter. A number in the reference range does not mean optimal for that individual, and a number below it without symptoms does not automatically require treatment. The diagnosis is the combination of a consistently low measurement and a compatible clinical picture.
Where supplements sit in this
If measurements are consistently low and symptoms are present, that is a medical matter and warrants a physician rather than a supplement. Clinically low testosterone has causes that need identifying, some of which are serious.
The category we review addresses a different situation: men whose levels are within range but at the lower end, with correctable deficiencies or lifestyle factors. That is a legitimate space for nutritional support, and a much narrower claim than most marketing makes. Our comparative review is written for that reader.
References
- 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.
- Mulhall JP, Trost LW, Brannigan RE, et al. Evaluation and management of testosterone deficiency: AUA guideline. Journal of Urology. 2018;200(2):423-432.