Free vs. Total Testosterone: Which Number Actually Matters?
You get your testosterone checked.
Your total testosterone is 550 ng/dL.
You’re told:
“Your testosterone is normal.”
But you’re exhausted.
Your sex drive has dropped. Erections aren’t what they used to be. You’re struggling to maintain muscle. Recovery feels slower. Motivation is down.
Then someone finally checks your free testosterone.
It’s low.
So which number is correct?
Both of them may be.
And that is exactly why understanding the difference between total testosterone and free testosterone matters.
For many men, a total testosterone level gives us a useful first look at androgen status. But it does not tell the entire story—especially when a protein called sex hormone-binding globulin, or SHBG, is unusually high or low.
In those situations, two men can have essentially the same total testosterone level but very different amounts of testosterone available to their tissues.
This is one reason I rarely view testosterone as a single number and neither should you (or your doctor).
Understanding testosterone levels males more sense within a broader context of testosterone and hormone health.
What Is Total Testosterone?
Total testosterone represents essentially all of the testosterone circulating in your blood at the time the sample is taken.
But nearly all of that testosterone is attached to proteins.
Circulating testosterone exists primarily in three forms:
Testosterone tightly bound to SHBG
Testosterone more loosely bound to albumin
A small amount of completely unbound, or free, testosterone
Depending on the population and methodology used, only roughly 1–4% of circulating testosterone is free.
So when your laboratory reports:
Total testosterone: 600 ng/dL
that does not mean all 600 ng/dL is freely available to interact with androgen receptors.
Total testosterone is essentially the size of the entire testosterone pool.
The important next question is:
How much of that pool is actually available?
What Is Free Testosterone?
Free testosterone is testosterone that is not bound to SHBG or albumin.
It represents only a small fraction of circulating testosterone, but it is particularly important when trying to understand a man’s androgen status.
Testosterone bound tightly to SHBG is considerably less available for immediate tissue action. Testosterone bound loosely to albumin can dissociate relatively easily and is often grouped with free testosterone under the term bioavailable testosterone.
An easy way to think about it:
Total testosterone = all the money in the account.
Free testosterone = the money you can readily spend.
You could technically have a large account balance while having surprisingly little accessible cash.
That is where SHBG enters the picture.
SHBG: The Number That Often Explains the Confusion
Sex hormone-binding globulin SHBG is a protein produced primarily by the liver.
It binds testosterone with relatively high affinity.
That means changes in SHBG can substantially change the relationship between your total testosterone and your free testosterone.
This can create several very different-looking hormonal profiles.
Man A
Total testosterone: 550 ng/dL
SHBG: 25 nmol/L
Free testosterone: healthy
Man B
Total testosterone: 550 ng/dL
SHBG: 90 nmol/L
Free testosterone: low
On paper, both men have exactly the same total testosterone.
Physiologically, their hormonal environments may be quite different.
Current European Association of Urology guidance specifically recommends measuring SHBG and calculating free testosterone when conditions that alter SHBG may be present.
The Endocrine Society likewise recommends assessing free testosterone when SHBG-altering conditions exist or when total testosterone sits near the lower end of the reference range.
This isn’t fringe hormone medicine.
It is standard endocrine physiology.
Can You Have Normal Total Testosterone but Low Free Testosterone?
Yes.
And this is one of the most important clinical scenarios to understand.
Imagine a man with:
Total testosterone: 575 ng/dL
If the laboratory reference range is approximately 300–1,000 ng/dL, somebody looking only at total testosterone might immediately say:
“Your testosterone is fine.”
But now imagine:
SHBG: 105 nmol/L
His total testosterone may look reassuring partly because a large amount of testosterone is being carried by SHBG.
His free testosterone could still be low.
That doesn’t automatically mean he needs testosterone therapy.
It means his evaluation is incomplete if the clinician ignores the discrepancy.
Symptoms, repeat measurements, SHBG, free testosterone, LH, FSH, prolactin, thyroid function, medications, metabolic health and other factors may all become relevant.
High SHBG: When Total Testosterone Can Look Better Than the Clinical Picture
When SHBG rises, more testosterone becomes bound.
Total testosterone may consequently appear relatively preserved—or sometimes quite high—while free testosterone falls.
Conditions associated with higher SHBG include:
Aging
Hyperthyroidism
Certain liver diseases
Estrogen exposure
Certain anticonvulsants
Some other medications and medical conditions
The 2026 European Association of Urology guideline specifically lists aging, hyperthyroidism, hepatic disease, smoking, HIV/AIDS, estrogen exposure, thyroid hormone and anticonvulsants among factors that may raise SHBG.
This is precisely why a total testosterone level cannot always be interpreted in isolation.
Low SHBG Can Create the Opposite Problem
The opposite scenario occurs when SHBG is low.
Imagine:
Total testosterone: 310 ng/dL
SHBG: 10 nmol/L
Free testosterone: relatively preserved
Looking only at the total testosterone could make this man appear significantly testosterone deficient.
But low SHBG means less testosterone is tied up by SHBG.
His available testosterone may therefore be considerably better than the total testosterone suggests.
Low SHBG is commonly seen with conditions such as:
Obesity
Insulin resistance
Type 2 diabetes/metabolic syndrome
Hypothyroidism
Nonalcoholic fatty liver disease
Glucocorticoid exposure
Androgen exposure
Certain other metabolic conditions
The EAU specifically recommends incorporating SHBG and free testosterone into assessment in these situations.
This creates an important clinical distinction:
A low total testosterone does not always mean the same thing physiologically.
Obesity Is a Great Example
Obesity can make testosterone interpretation especially complicated.
Men with obesity frequently have lower SHBG.
When SHBG falls, total testosterone can also fall—even when free testosterone is less dramatically reduced.
The Society for Endocrinology has specifically highlighted this situation, noting that men with obesity can have a mildly low total testosterone while relatively preserved androgenicity because SHBG is also low.
This matters because the appropriate first treatment for some men may not necessarily be testosterone.
It could include addressing:
Weight
Insulin resistance
Sleep apnea
Poor sleep
Alcohol
Medications
Nutrition
Physical inactivity
Other metabolic disease
There is an important difference between optimizing testosterone physiology and simply prescribing testosterone.
High SHBG Can Be Just as Important
Now consider the opposite patient.
He’s lean.
Active.
Maybe 45 years old.
His total testosterone is 620 ng/dL.
Everyone keeps telling him his hormones look great.
But his SHBG is 95 nmol/L.
His free testosterone is substantially lower than expected.
That result deserves more investigation.
Why is the SHBG high?
Does he have thyroid disease?
Liver abnormalities?
Medication effects?
Age-related changes?
Nutritional issues?
Is the laboratory measurement reliable?
Are his symptoms actually compatible with androgen deficiency?
That is a much better clinical discussion than simply declaring:
“620 is normal.”
Does Free Testosterone Matter More Than Total Testosterone?
This is where the discussion requires some nuance.
You will occasionally see claims online such as:
“Total testosterone doesn’t matter. Only free testosterone matters.”
I would not go that far.
Total testosterone remains the standard initial measurement in most major guidelines.
The Endocrine Society recommends diagnosing hypogonadism only in men who have compatible symptoms plus consistently low testosterone concentrations, with repeat morning testing. Free testosterone is incorporated when appropriate—particularly when SHBG abnormalities could distort interpretation.
Similarly, current EAU guidance still uses total testosterone as a central part of diagnosis while recommending free testosterone assessment when SHBG is altered.
So this should not become:
Total vs. free testosterone.
It should become:
Total + free testosterone + SHBG + symptoms + clinical context.
That is a much more useful framework.
Why Doctors Usually Start With Total Testosterone
There are several reasons.
Total testosterone assays are:
Widely available
Better standardized
Familiar to clinicians
Supported by decades of research
Incorporated into major guidelines
Easier to interpret across large populations
Testosterone also varies considerably from day to day.
Levels can be influenced by:
Time of day
Sleep
Acute illness
Food intake
Calorie restriction
Training stress
Medications
Weight changes
This is why testosterone deficiency generally should not be diagnosed from a random single blood draw.
The Endocrine Society recommends repeating morning fasting total testosterone measurements on separate occasions when evaluating suspected hypogonadism.
How Should Free Testosterone Be Measured?
This gets surprisingly complicated.
There isn’t one universally interchangeable “free testosterone” test.
Equilibrium Dialysis
Equilibrium dialysis is generally considered the reference or gold-standard approach for directly measuring free testosterone.
It physically separates free testosterone from protein-bound testosterone.
The downside?
It is technically demanding and not routinely available through every laboratory.
Calculated Free Testosterone
Because equilibrium dialysis is difficult to perform routinely, clinicians often calculate free testosterone using measurements including:
Total testosterone
SHBG
Albumin
Different mathematical models exist.
Calculated free testosterone isn’t perfect, but it can be clinically useful—particularly when SHBG is unusually high or low.
The Endocrine Society specifically recognizes either equilibrium-dialysis measurement or calculation using total testosterone, SHBG and albumin when free testosterone assessment is indicated.
Be Careful Comparing Free Testosterone Numbers Between Laboratories
This is extremely important.
You may see one laboratory report free testosterone as:
8.7 ng/dL
another as:
87 pg/mL
and another using an entirely different reference interval.
Different assays and calculation techniques may produce different values.
That’s why Googling:
“What should my free testosterone be?”
and comparing your result to a random number posted online can be misleading.
The method matters.
The units matter.
The laboratory matters.
The reference population matters.
And the clinical context still matters.
What Is a Normal Free Testosterone Level?
There is no single universally applicable free-testosterone cutoff that should be applied blindly to every laboratory.
The EAU notes limited evidence supporting approximately 220 pmol/L 6\.4 ng/dL as a possible free-testosterone threshold in appropriate clinical settings, while emphasizing the importance of SHBG and proper testosterone assessment.
But that number should not become another simplistic diagnostic line.
A laboratory value should be interpreted using the method and reference range of the laboratory that generated it.
More importantly:
Low testosterone is a clinical diagnosis—not merely a laboratory diagnosis.
What About a Total Testosterone of 300–400?
This is where free testosterone becomes particularly useful.
A testosterone level in the 300-400 range can be especially difficult to interpret without looking at age, symptoms, SHBG, and free testosterone.
A total testosterone of:
305
340
375
410
may not tell us enough by itself.
Suppose two 35-year-old men both have a total testosterone of 375 ng/dL.
One has:
SHBG: 12
The other has:
SHBG: 70
Their free testosterone levels could be dramatically different.
Their underlying physiology may be different.
And the appropriate evaluation may be different.
This is why the question:
“Is 350 testosterone normal?”
isn’t nearly as simple as it sounds.
Symptoms Still Matter
Neither total nor free testosterone should be interpreted without asking how the patient actually feels.
Symptoms potentially associated with testosterone deficiency can include:
Reduced libido
Fewer spontaneous or morning erections
Erectile dysfunction
Reduced energy
Reduced exercise performance
Loss of muscle or strength
Increased body fat
Reduced motivation
Mood changes
Difficulty concentrating
Reduced bone density
Anemia in some men
But here’s the problem:
Almost none of those symptoms belongs exclusively to testosterone deficiency.
Fatigue can come from sleep apnea.
Poor libido can come from depression.
ED can be vascular.
Poor gym performance can result from inadequate sleep or calories.
Brain fog can have dozens of causes.
That is why symptoms alone don’t diagnose low testosterone either.
The diagnosis requires combining the clinical picture with appropriate laboratory testing.
Testosterone Is a System, Not a Number
When I evaluate a man with possible testosterone deficiency, I don’t want to know only his testosterone level.
I want to understand his androgen physiology.
Depending on the situation, that may mean evaluating:
Total testosterone
Free testosterone
SHBG
LH
FSH
Estradiol
Prolactin
Thyroid function
CBC/hematocrit
Metabolic health
Sleep
Medications
Fertility goals
Symptoms
LH and FSH are particularly useful because they help answer a different question:
Why is testosterone low?
Is the testicle failing to produce adequate testosterone despite strong stimulation?
Or is the pituitary/hypothalamic signal itself inadequate?
Major guidelines recommend LH—and often FSH depending on the context—as part of distinguishing primary from secondary hypogonadism.
That distinction can matter tremendously.
Example 1: Normal Total Testosterone, Low Free Testosterone
Consider:
Total testosterone: 610 ng/dL
SHBG: 95 nmol/L
Free testosterone: low
Symptoms: low libido, reduced morning erections, fatigue
A simplistic interpretation:
“610 is great. You’re normal.”
A more complete interpretation:
His total testosterone does not necessarily reflect the amount of testosterone available outside the SHBG-bound pool.
Next steps might include evaluating why SHBG is elevated, confirming the measurements, assessing symptoms and looking for alternative explanations.
That does not automatically mean he needs TRT.
However, it does NOT automatically mean he is NOT a TRT candidate either.
It means he deserves a real evaluation.
Example 2: Low Total Testosterone, Reasonable Free Testosterone
Now consider:
Total testosterone: 315 ng/dL
SHBG: 11 nmol/L
Free testosterone: preserved
BMI: 34
Insulin resistance present
The total testosterone looks low.
But extremely low SHBG may be contributing significantly to that result.
Before labeling this man permanently hypogonadal, I would want to understand his:
Weight
Metabolic health
Sleep
Sleep apnea risk
Medications
Alcohol intake
Nutrition
Repeat morning testosterone levels
LH/FSH
Treating the underlying metabolic environment may significantly change his testosterone physiology.
Example 3: Both Total and Free Testosterone Are Low
Consider:
Total testosterone: 225 ng/dL
Free testosterone: low
SHBG: normal
Symptoms: reduced libido, ED, fatigue
Repeat morning level: similarly low
Now the biochemical picture is considerably more convincing.
The next questions become:
Why is it low?
Is this primary or secondary hypogonadism?
Are there reversible causes?
Does he want future fertility?
Are there contraindications to testosterone therapy?
What treatment approach makes sense?
That is how testosterone medicine should work.
Not:
Low number → testosterone prescription.
And not:
Number above 300 → you’re fine.
Can You Have Low Free Testosterone With No Symptoms?
Absolutely, although I don’t personally see that very often.
Lab abnormalities should not automatically become diseases.
Someone can have a free testosterone value near or even below a laboratory reference range and feel completely well.
The Endocrine Society explicitly emphasizes that the diagnosis of hypogonadism requires both compatible symptoms/signs and consistently low testosterone concentrations.
Treat the patient.
Understand the labs.
Don’t treat an isolated number.
Can You Have Symptoms With Normal Free Testosterone?
Yes.
And this may be even more important.
Suppose someone has:
Total testosterone: 650
Free testosterone: excellent
Normal SHBG
but feels tired, unmotivated and has erectile dysfunction.
Testosterone should not automatically become the explanation.
You may need to look at:
Sleep apnea
Cardiovascular disease
Blood pressure
Diabetes
Depression/anxiety
Medication side effects
Thyroid dysfunction
Relationship factors
Overtraining
Under-fueling
Alcohol
Other medical disease
Testosterone is important.
But not every male symptom is caused by testosterone.
So Which Testosterone Number Matters Most?
If you’re looking for one magic number, you’re asking the wrong question.
Total testosterone tells us:
How much testosterone is circulating overall.
SHBG tells us:
How much of that testosterone may be tightly bound.
Free testosterone helps tell us:
How much testosterone remains unbound and potentially available.
LH and FSH help tell us:
Why testosterone may be low.
Symptoms tell us:
Whether the laboratory findings are clinically meaningful.
The most useful answer usually comes from putting those pieces together.
The Bigger Problem With Testosterone Testing
Unfortunately, many men experience one of two extremes.
Extreme #1: Testosterone is ignored
A man has symptoms.
One total testosterone level comes back at 340.
He is told:
“That’s normal.”
No repeat measurement.
No SHBG.
No free testosterone.
No LH.
No fertility discussion.
No explanation.
Extreme #2: Testosterone is oversimplified
A man sees an online clinic.
His testosterone is 450.
He checks several boxes on a symptom questionnaire.
He receives testosterone.
No meaningful investigation into the cause.
No real discussion of fertility.
No consideration of other medical issues.
Neither approach represents good men’s health care.
The goal should be an accurate diagnosis followed by an individualized discussion of options.
The Bottom Line: Free vs. Total Testosterone
Total testosterone is important.
Free testosterone is important.
SHBG is important.
But none should automatically be interpreted alone.
For many men, total testosterone provides a perfectly reasonable starting point.
For others—particularly men with borderline testosterone levels or unusually high or low SHBG—free testosterone can significantly change how the laboratory picture is interpreted.
So if you’ve been told:
“Your testosterone is normal.”
but you still have significant symptoms, the next question may not necessarily be:
“How do I raise my testosterone?”
It may be:
“Do we actually understand my testosterone physiology yet?”
That is a much better place to start.
Think Your Testosterone Numbers Don’t Tell the Whole Story?
At Fit & Fine Health, we look beyond a single testosterone value.
Our men’s health evaluation can include assessment of total testosterone, free testosterone, SHBG and other important markers to better understand why you feel the way you do, rather than treating a laboratory number in isolation.
Start Your Men’s Health Assessment
David Hall, MD, CWC
Founder, Fit & Fine Health
This article is intended for general educational purposes and is not individualized medical advice. Testosterone symptoms can overlap with many other medical conditions. Diagnosis and treatment decisions should be made with a qualified healthcare professional after appropriate evaluation.