Testosterone numbers and what they actually mean

A total testosterone result on its own is the least useful number in men's health. It is quoted in reviews as if it is the answer. It is, at best, the opening question. A thorough male hormone panel has six or seven components, and the interplay between them is what drives clinical decisions. This article explains each one in plain terms and why a single result is never enough to act on.

Total testosterone

Total testosterone is the sum of free testosterone, albumin-bound testosterone, and SHBG-bound testosterone. UK labs usually report it in nmol/L with a reference range somewhere around 8 to 30, though the upper end varies. Guidelines (BSSM, Endocrine Society) typically use two thresholds: above 12 nmol/L is usually reassuring, below 8 nmol/L is concerning, and the 8 to 12 zone needs free testosterone plus clinical judgement.

Total testosterone has a strong diurnal pattern. It peaks between 7 and 10 AM and is substantially lower by late afternoon. A reliable measurement is taken before 11 AM, ideally fasting. Evening tests are routinely misleading, and we sometimes see men diagnosed on an evening reading that would have been clearly normal in the morning.

SHBG (sex hormone binding globulin)

SHBG is the protein that binds and effectively inactivates most circulating testosterone. It rises with age, with thyroid overactivity, with liver disease, with some medications (anticonvulsants, oestrogens, androgen blockers). It falls with obesity, insulin resistance, diabetes, hypothyroidism, and corticosteroids.

Why it matters: if your SHBG is high, much of your total testosterone is locked up and unavailable. A man with total T of 11 and SHBG of 70 has less bioavailable hormone than a man with total T of 9 and SHBG of 30. Diagnosing hypogonadism on total testosterone alone misses this entirely.

Free testosterone

Free testosterone is the fraction that is not bound to anything and can act on target tissues. It is the biologically active pool. UK labs rarely measure it directly (the direct assay is technically difficult); we usually calculate it from total testosterone, SHBG, and albumin using the Vermeulen equation.

Reference ranges for calculated free T are roughly 225 to 650 pmol/L, though your lab's range will be printed on the report. Free testosterone below roughly 220 pmol/L with consistent symptoms is a strong pointer to hypogonadism, even if total T is borderline.

LH and FSH

Luteinising hormone (LH) and follicle stimulating hormone (FSH) are pituitary hormones that drive testicular function. LH stimulates testosterone production; FSH supports sperm production. Their pattern tells us where the problem is.

Primary (testicular) hypogonadism: testosterone is low, LH and FSH are high. The testes are failing and the pituitary is shouting at them to work harder. Causes include Klinefelter syndrome, mumps orchitis, vasectomy complications, chemotherapy, testicular injury, haemochromatosis.

Secondary (hypothalamic-pituitary) hypogonadism: testosterone is low, LH and FSH are low or inappropriately normal. The signal from the brain is not reaching the testes. Causes include obesity (the most common), opioid use, pituitary tumour, hyperprolactinaemia, severe chronic illness, head injury.

The distinction matters because investigation, management, and sometimes prognosis differ. Secondary hypogonadism from obesity or opioids is often fully reversible. Primary hypogonadism is generally not.

Oestradiol (E2)

Testosterone is aromatised into oestradiol in fat tissue, muscle, and brain. Men need oestradiol for bone health, libido (yes, libido), and mood. Too little is a problem. Too much, particularly with heavy body fat, causes gynaecomastia, water retention, and low mood.

We measure E2 at baseline and monitor it on TRT. In larger men with higher body fat, E2 can rise disproportionately on testosterone replacement and sometimes needs management with an aromatase inhibitor (anastrozole) in low dose.

Prolactin

Prolactin is the catch-for-the-rare-cause marker. A prolactin-secreting pituitary tumour (prolactinoma) suppresses LH and FSH and produces secondary hypogonadism. Missing a prolactinoma and giving TRT treats the downstream effect while the tumour grows. We always measure prolactin in initial hypogonadism workup, and any significantly elevated reading (typically over 1000 mIU/L) triggers pituitary MRI.

Why one blood test is never enough

Testosterone varies day to day by 15 to 20 percent even when measured at the same time in the morning. A single reading that is slightly below range might be within range on a repeat. A single reading that is mid-range might be below range next week. Guidelines require two separate morning tests for diagnosis.

We also check that the blood draw was done correctly. Repeated tourniquet use can shift SHBG. Recent acute illness, severe sleep deprivation, or alcohol binge within 48 hours distort results. Severe stress (bereavement, acute infection) suppresses testosterone for weeks.

What a good hormone panel looks like

At LoveMyLife, a full male hormone panel includes: total testosterone, SHBG, calculated free testosterone, LH, FSH, oestradiol, prolactin, plus TSH, fasting glucose, HbA1c, and full blood count. The cost is £149 as a standalone panel or included in both our online and in-person assessment tiers. Results come back with a written clinical interpretation, not just lab numbers and a reference range.

The honest bottom line

Testosterone numbers are interesting but meaningless on their own. A proper hormone panel, two readings taken correctly, and a clinician who understands the interplay is what tells you whether you have a problem and what to do about it.

Ready to start?

If this article has made you think an assessment might help, the next step is a short consultation with one of our men's health doctors.

Begin your consultation at this link. Online or in person at Westfield London.