Hormones
SHBG Levels by Age: Why Free Testosterone Falls Faster Than Total
Reviewed by a qualified clinician · analysed at UKAS-accredited UK labs (ISO 15189)
Last reviewed August 20266 min read
Every Helvy guide is written by our health editors, then checked by a qualified clinician before it goes live and re-checked as the science moves. We name clinical roles, not individuals, until each reviewer has agreed to be credited publicly. This is wellness guidance to help you understand your own data, not a diagnosis.
QUICK ANSWER
No UK lab prints an SHBG range by age for adults. Men get one adult range, roughly 17 to 78 nmol/L. What changes is the average. SHBG climbed about 1.6% a year in the Massachusetts Male Aging Study, which is why free testosterone falls faster than total testosterone.
Not sure which markers you need? Build your test →Your testosterone came back normal. You are 54, you are flat by mid-afternoon, and the report says there is nothing to see. Then you spot a second line further down. SHBG, 64 nmol/L. Nobody explained that one.
SHBG is sex hormone-binding globulin, the protein that carries testosterone around your blood. Bound testosterone is parked. Only the free fraction reaches your tissues. And SHBG is one of the few markers that genuinely shifts as you get older.
1. Is there an SHBG range for your age?
Not for adults, no. UK labs give men over 18 a single range and leave it there. Women get one split, set around the menopause. That is the whole of the age banding on a real report.
Two NHS laboratories show how much the printed figures move between sites.
| Group | Oxford University Hospitals | North Bristol |
|---|---|---|
| Men, any adult age | 17 to 78 | 13 to 90 |
| Women, reproductive years | 34 to 148 (19 to 49) | 18 to 136 (18 to 46) |
| Women, later years | 26 to 118 (over 49) | 17 to 125 (47 and over) |
Notice the disagreement. Oxford flags a man above 78. North Bristol waits until 90. Same blood, two verdicts. So read your number against the range printed beside it, never one you found online. Our guide to reference ranges explains why that gap exists.
2. What actually changes with age?
The average, not the range. The Massachusetts Male Aging Study followed men aged 40 to 70 and measured this directly. SHBG rose about 1.6% a year. Total testosterone fell about 0.8% a year.
Put those two together and the arithmetic turns awkward. More carrier protein, less hormone to carry. In the same study, free and albumin-bound testosterone fell about 2% a year. That is roughly twice the rate of the total.
So a man of 60 can hold the same total testosterone he had at 40 and still have less of it available. The total number hides the change. SHBG is where it shows up. Our testosterone levels by age guide covers the other half of the same picture.
3. Can a normal total testosterone still leave you short?
It can, and UK guidance says so plainly. The British Society for Sexual Medicine draws its practical line at a total testosterone below 12 nmol/L, or a free testosterone below 225 pmol/L, on two separate morning samples.
The same guideline is specific about when SHBG belongs in the picture. It says SHBG should be checked “where TT levels are borderline, or low to normal, particularly in obese and older men”, and that free testosterone should be measured where SHBG is known or suspected to be abnormal.
Free testosterone is rarely measured head on. It is calculated, from total testosterone, SHBG and albumin. Take SHBG out and there is no sum to do. That is why a borderline testosterone result read on its own tells you so little, and why the free fraction is the number clinicians reach for next.
4. Is age the biggest thing moving your SHBG?
Usually not, and this is the part worth carrying away. The same UK guideline is blunt about it.
“The age-related rise in SHBG does cause a fall in FT and bioavailable testosterone, but the increased rates of TD seen in older men are primarily related to an increased prevalence of obesity, T2DM and chronic illness.”
— British Society for Sexual Medicine Guidelines on Male Adult Testosterone Deficiency, 2023
FT is free testosterone. TD is testosterone deficiency. T2DM is type 2 diabetes. In plain terms: age nudges SHBG up, but weight and metabolic health move it further, and they move it down.
SHBG tends to sit higher with an overactive thyroid, with liver disease, with oral oestrogen and at low body weight. It tends to sit lower with weight carried around the middle, with an underactive thyroid and with insulin resistance.
None of that is a verdict on you. It is the reason a single SHBG reading needs the rest of your results beside it, and a qualified clinician to read the set together.
5. How does age affect SHBG in women?
Women get the one age split the labs do make. Oxford uses 34 to 148 nmol/L up to 49, then drops to 26 to 118 above it. North Bristol splits at 47 instead. The split is a nod to the menopause, not a year-by-year chart.
What moves a woman’s SHBG most is often not age at all. It is what she takes. Oral oestrogen passes through the liver first, and the liver answers by making more SHBG. One trial in the Journal of Clinical Endocrinology & Metabolism found oral estradiol raised SHBG by 67 to 171%. Transdermal estradiol did not.
So the same woman on a patch and on a tablet will not produce the same number. Low SHBG runs the other way, and often turns up alongside the markers discussed around PCOS. The main SHBG guide covers high and low readings in full.
6. Which blood test measures your SHBG?
Helvy’s Complete Male Hormones panel (£119) reports SHBG alongside total testosterone, free testosterone, the free androgen index, albumin, LH, FSH, prolactin and DHEA-S. That grouping is the point. SHBG on its own answers very little.
The Hormone Balance panel (£99) reports SHBG with FSH, LH, total testosterone and the free androgen index. Both are home finger-prick tests, processed by UKAS-accredited UK labs. Take your sample in the morning, when testosterone is at its peak.
Not sure which one fits? The build-my-test tool walks you through it, and the men’s hormones hub covers what else is worth reading alongside it.
READY TO TEST?
See the number behind your testosterone
Helvy’s home blood tests report SHBG with plain-English context, so a normal-looking total never leaves you guessing. Samples are processed by UKAS-accredited UK labs.
Frequently asked questions
What is a normal SHBG level by age in the UK?
There is no age-banded range for adults. UK labs give men over 18 one range, around 17 to 78 nmol/L at Oxford and 13 to 90 at North Bristol. Women get a single split near the menopause. Always read your result against your own lab’s printed range.
Does SHBG go up with age?
On average, yes. The Massachusetts Male Aging Study followed men aged 40 to 70 and found SHBG rose about 1.6% a year, while total testosterone fell about 0.8% a year. The line on the report does not move. The population average does.
Why does free testosterone fall faster than total testosterone?
Because two things move at once. Total testosterone drifts down while SHBG drifts up, so a larger share of what is left sits bound. In the same study, free and albumin-bound testosterone fell about 2% a year, roughly twice the rate of the total.
Is high SHBG at 60 something to worry about?
Not on its own. High SHBG means more of your testosterone is bound, so the free fraction reads lower than the total suggests. It is read alongside total and free testosterone, not by itself. Take an out-of-range result to a qualified clinician or your GP.
What lowers SHBG?
Weight carried around the middle, insulin resistance and an underactive thyroid all tend to pull SHBG down. UK guidance notes that rising rates of obesity and type 2 diabetes explain more of the picture in older men than age alone does.
Does HRT change your SHBG reading?
The route matters. A trial published in the Journal of Clinical Endocrinology & Metabolism found oral estradiol raised SHBG by 67 to 171%, while transdermal estradiol did not. Tell your clinician what you take, and how you take it.
Related guides
SHBG Blood Test UK
High and low readings, the insulin resistance link, and the full picture.
Testosterone Levels by Age
What a normal total testosterone looks like at 30, 40, 50 and beyond.
Free Testosterone Explained
Why the calculated free fraction often matters more than the total.
Borderline Testosterone
What to do when your result sits just inside the printed range.
Free Androgen Index
The ratio that puts testosterone and SHBG into one number.
Men's Hormones Hub
Every guide on testosterone, SHBG and the hormones around them.
Test for this
Keep reading