SHBG for Men Over 40: The Executive's Guide to the Hormone Binding Protein That Decides How Much Testosterone You Can Actually Use
Your total testosterone came back at 550 ng/dL. Your GP nodded. Yet you still wake up flat, train hard with nothing to show for it, and feel mentally blunt by 3pm. The number on the page lied — not because the lab was wrong, but because nobody told you about SHBG for men over 40. This is the protein that decides how much of your testosterone is actually doing anything, and after 40 it climbs about 1% every year — quietly turning a "normal" result into a useless one.
What SHBG Actually Is
SHBG — sex hormone-binding globulin — is a protein your liver makes that latches onto sex hormones and pulls them out of active circulation. Roughly 98% of the testosterone in your bloodstream is bound. Most of that is held tightly by SHBG. Only the unbound fraction — your free testosterone — can enter cells and do work.
Think of total testosterone as cash in a bank account. SHBG is the lock-up period. If most of your cash is in a 10-year fixed deposit, your spending power right now is small — even if the total balance looks healthy. That's why two men with identical total testosterone can present completely differently. One trains well, sleeps deep, and runs his company at pace. The other can't get out of bed.
Why SHBG Matters More After 40
SHBG drifts upward with age. The published data shows median SHBG rising from around 21 nmol/L in younger men to around 45 nmol/L in older men — roughly a 1% climb per year. Stack that on top of the gradual fall in total testosterone most men see after 40, and the gap between what your blood test reports and what your body can actually use widens every year.
This is the exact mechanism that catches out executives. You optimise your training, dial in your sleep, sort your nutrition — and your total testosterone still sits in the 500s. You feel like the protocol isn't working. The protocol is fine. Your free fraction is being eaten by rising SHBG, and nobody is measuring it.
If you've read free testosterone vs total testosterone for men over 40, this is the missing piece. SHBG is the variable that decides the relationship between the two.
The Optimal SHBG Range for Men Over 40
Standard lab reference range for adult men is 10–57 nmol/L. That range is too wide to be useful — it includes both metabolically sick men and overstressed lean men.
The functional sweet spot for most men over 40 sits between 20 and 35 nmol/L. Inside that band you typically see healthy free testosterone, stable energy, normal libido, and good body composition response to training. Outside it, something is usually wrong.
- Below 20 nmol/L — almost always a metabolic flag. Insulin resistance, visceral fat, fatty liver.
- Above 40 nmol/L — usually a stress, undernutrition, alcohol, thyroid, or medication signal.
- Above 50 nmol/L — your free testosterone is almost certainly suppressed regardless of total.
A single SHBG number tells you very little on its own. Always read it next to total testosterone, free testosterone, fasting insulin, and a liver panel.
What High SHBG Means in an Executive
High SHBG is the more common pattern in lean, hard-charging men over 40 who eat clean, train hard, and drink "moderately." The drivers:
- Chronic under-eating — particularly low carbohydrate intake on training days
- Excessive endurance training without adequate recovery
- Daily alcohol — even at one or two drinks
- Hyperthyroidism or subclinical thyroid issues
- Liver stress — fatty liver, NAFLD, hepatitis
- Certain medications — statins, anticonvulsants, some hormonal treatments
- Growth hormone decline
- Ageing itself
The classic executive presentation: 47, lean, runs 40km a week, drinks two glasses of red most nights, eats mostly chicken and salad. Total T sits at 580. Free T is rock bottom. He thinks he needs TRT. He doesn't. He needs to eat more carbs, train less, drink less, and re-test in 90 days.
For the alcohol piece specifically, see alcohol and testosterone in men over 40.
What Low SHBG Means in an Executive
Low SHBG is the metabolic pattern. It's the executive who's gained 12kg of soft mass in five years, sleeps badly, snores, and runs his blood pressure on the high side. The drivers:
- Insulin resistance — the dominant cause
- Visceral fat and metabolic syndrome
- Non-alcoholic fatty liver disease
- Hypothyroidism
- Anabolic steroid use — past or present
- Very high carbohydrate intake from refined sources
When SHBG is low and total testosterone looks normal, free testosterone can look misleadingly fine — but the underlying picture is metabolic decline, and free T will collapse within a few years if nothing changes. Low SHBG is a longevity flag long before it's a hormone flag. Pair the reading with fasting insulin for men over 40 and visceral fat in men over 40 and the picture becomes obvious.
How to Lower High SHBG Without TRT
If your SHBG sits in the 50s or 60s and your free testosterone is suppressed, the leverage points are clear before you ever consider exogenous testosterone.
- Eat more carbohydrate, particularly on training days. Most lean, high-SHBG executives are unknowingly running a chronic energy deficit. Add 100–150g of starchy carbs around training.
- Cap alcohol. Two drinks twice a week, not two drinks daily. Liver load drives SHBG.
- Resistance train hard, three to four sessions a week. Heavy compound lifts blunt SHBG.
- Cut excess endurance volume. If you're running 50+ km a week and feel flat, that's the problem.
- Check thyroid. TSH, free T3, free T4. Subclinical hyperthyroidism is a common hidden driver.
- Boron 6–10mg daily. Small but consistent evidence base for modestly lowering SHBG.
- Get protein right — not too low, not extreme. Aim for 1.6–2.0 g/kg.
Re-test SHBG, total T, and free T at 90 days. If the protocol is right, you'll see SHBG drop into the 30s and free testosterone rise — without touching exogenous hormones.
How to Raise Low SHBG Without Drugs
Low SHBG is harder to "treat" in isolation because it's a symptom of metabolic disease. You don't raise SHBG — you fix the underlying picture and SHBG comes back to normal.
The core moves: drop visceral fat, restore insulin sensitivity, sort sleep, eliminate the alcohol drip, build muscle. Strength training, Zone 2 cardio, and reducing refined carbohydrate intake do more for low SHBG than any supplement on the market.
How to Test SHBG Properly
Don't test SHBG in isolation. Order it as part of a panel that includes:
- Total testosterone
- Free testosterone (calculated or direct)
- Albumin
- Fasting insulin and HbA1c
- TSH, free T3, free T4
- ALT, AST, GGT (liver)
- Lipids and ApoB
Draw blood between 7am and 9am, fasted, on a day you haven't trained hard. Repeat in 90 days if you're running a protocol. One reading is a data point. Two readings is a trend.
FAQ
Can you have normal total testosterone and still feel low T? Yes — and high SHBG is the most common reason. If your total testosterone is in the 500s and you feel symptomatic, get SHBG and free testosterone tested.
Does TRT fix high SHBG? TRT lowers SHBG in most men. But starting TRT to mask a high-SHBG picture caused by undernutrition or overtraining is treating the symptom, not the cause. Fix the inputs first.
Does intermittent fasting raise SHBG? Prolonged or aggressive fasting can. If you're a lean man over 40 with high SHBG already, daily 18-hour fasts are usually the wrong protocol.
Is high SHBG dangerous? Not directly. The risk is what it represents — a suppressed free testosterone, often combined with underfueling — and what that does to your training response, mood, libido, and cognition over years.
How fast can SHBG change? Meaningfully in 8–12 weeks if the inputs change. Don't re-test sooner than 90 days unless you've had a major medication or thyroid change.
The Bottom Line
After 40, total testosterone is the wrong number to optimise around. SHBG is the silent variable that decides whether your testosterone is doing anything for you, and it drifts the wrong way every year you don't pay attention to it. Get the panel right. Read SHBG against the rest of your bloods. Then make the boring changes — protein, carbs, alcohol, sleep, lifting — that move the number back where it should be.
If you're done guessing at your bloods and want a programme that actually reads them in context — diet, training, sleep, recovery, hormones — that's the Optimization Programme. Book a consultation and we'll start with your numbers.