When your GP orders a testosterone test, they typically measure one thing: total testosterone. It’s a single number on a broad reference range. If you fall anywhere within “normal,” you’re told everything is fine. But that number alone doesn’t tell the full story.
The problem with total testosterone alone
Total testosterone includes both the bound and unbound fractions of the hormone circulating in your blood. Around 98% of testosterone is bound to proteins — primarily sex hormone-binding globulin (SHBG) and albumin. Only the remaining 2% is “free” and biologically active.
Two men can have identical total testosterone levels but vastly different symptoms. One may feel sharp, energised and strong. The other may be struggling with fatigue, brain fog and low motivation. The difference often lies in how much of that testosterone is actually available for the body to use.
What a complete panel looks like
A comprehensive assessment goes well beyond a single number. At Heracles, every testosterone panel includes:
- Total testosterone — the overall circulating level
- Free testosterone — the bioavailable fraction your body can actually use
- SHBG — the binding protein that determines how much testosterone is “locked up”
- Oestradiol — because testosterone converts to oestrogen, and the ratio matters
- LH & FSH — pituitary hormones that reveal whether the issue is primary or secondary
- Prolactin, thyroid function, HbA1c — to rule out other causes of similar symptoms
Why reference ranges can mislead
NHS reference ranges for testosterone typically span 8–29 nmol/L. That’s an enormous window. A 38-year-old man sitting at 9 nmol/L is technically “normal” but may be experiencing significant symptoms. Context matters: age, symptoms, lifestyle, body composition and other biomarkers all feed into the clinical picture.
“A number on its own means very little. It’s the clinical picture — symptoms, history, and a full panel — that tells us what’s actually going on.”
What to do next
If you’ve had a testosterone test through your GP and been told your levels are “normal” but you don’t feel normal, it’s worth looking deeper. A comprehensive panel gives you and your clinician the information needed to make an informed decision — not a guess based on a single data point.
