One of the most common situations we hear from men in their late forties and fifties: they've been to their GP with classic symptoms — energy down, drive down, gym performance down — and the doctor has run a blood test and said, gently, "your testosterone is in the normal range." The man goes home, feels confused, and slowly begins to convince himself that he's just getting older.

Sometimes that's true. Sometimes it isn't. The piece of the puzzle that's missing in this scenario, more often than not, is SHBG.

What SHBG actually is

SHBG stands for sex hormone-binding globulin. It's a protein, made by the liver, that circulates in your blood and binds tightly to testosterone (and oestradiol). Testosterone bound to SHBG is biologically inactive — it can't enter cells, it can't activate receptors, it can't do the things you actually want testosterone to do. It's parked.

The fraction of testosterone that isn't bound to SHBG is what's known as bioavailable testosterone, with the most active subset being free testosterone. This is typically only 1–4% of the total amount. It's the fraction that actually feels like testosterone in your body.

What goes wrong with age

Two things happen as men age, and both work in the same unfortunate direction:

  1. Total testosterone drifts down — roughly 1% per year after age 30, as we've covered elsewhere.
  2. SHBG drifts up — the liver produces more of it, partly due to age, partly due to insulin sensitivity, partly due to other shifts.

The combined effect is that free testosterone falls faster than total testosterone falls. A man whose total T dropped 15% over a decade might see his free T drop 25% or more in the same period — because his SHBG climbed at the same time.

This is why a blood test that only reports total testosterone can completely miss what's actually happening to a man's hormonal life.

The right blood panel to ask for

If you're a man over 40 with symptoms of low testosterone, the test order that actually answers the question is:

  • Total testosterone — the headline number.
  • SHBG — required to interpret the headline.
  • Free testosterone — calculated or measured directly, this is the active fraction.
  • Albumin — for accurate free T calculation.
  • Oestradiol — to check for excessive aromatisation, especially if you carry visceral fat.
  • LH and FSH — to distinguish primary (testicular) from secondary (pituitary) low T.

A good men's-health-aware doctor will run this panel without much pushing. Some GPs may need a polite conversation. Private men's-health labs in most EU countries will run it for somewhere between €80–150 — a small price for actually understanding what's happening in your body.

What SHBG numbers mean in practice

Reference ranges vary slightly by lab, but typically:

  • Below ~25 nmol/L: low SHBG. Often associated with insulin resistance, fatty liver, or excess body fat.
  • ~25–55 nmol/L: a generally healthy adult-male range.
  • Above ~70 nmol/L: elevated SHBG. Common in older men, men on certain medications, men with hyperthyroidism, or simply genetic variation.

If you're in the elevated range with normal total testosterone and low free testosterone, your problem is mostly SHBG, not production. That's a different intervention than the standard "you need TRT" answer.

What moves SHBG

The interventions that lower elevated SHBG, in rough order of impact:

  1. Improving insulin sensitivity — strength training, lower-carb periods, less alcohol, better sleep.
  2. Reducing visceral fat.
  3. Adequate protein intake — chronically low protein is associated with elevated SHBG.
  4. Adequate boron — surprisingly, a small mineral that has consistent effects on SHBG in trials.
  5. Specific botanicals — Tongkat Ali, in particular, has the most consistent evidence for SHBG modulation in middle-aged men.
A note on Testo Boost

The Tongkat Ali extract in Testo Boost is in the formula precisely because of its SHBG-modulating profile. For men whose total testosterone looks "normal" but whose free testosterone is suppressed by elevated SHBG, this is one of the few mechanisms that targets the specific problem rather than just attempting to push the total number higher.

The honest summary

If you've been told your testosterone is fine but you don't feel fine, ask for SHBG and free testosterone. The numbers are inexpensive, easy to obtain, and frequently the missing piece. Acting without them is acting blind.

Once you know your SHBG, your interventions can be targeted: lifestyle changes if it's elevated, medical follow-up if it's extremely high, and yes — supplemental support if the gap between total and free testosterone is the part of the picture that's actually broken.