What labs should I order to check testosterone?

At minimum: total testosterone, free testosterone, and SHBG. For a complete workup also order LH, FSH, prolactin, estradiol, and a comprehensive metabolic panel. Draw between 7am and 10am after a normal night's sleep, fasted is preferable. Repeat any abnormal result on a separate morning before drawing conclusions — testosterone fluctuates.

What's a normal testosterone reference range?

Most US labs use 264-916 ng/dL or 300-1000 ng/dL for total testosterone in adult men. The lower bound varies by lab and assay method (LC-MS/MS is the gold standard; immunoassay is more variable). Free testosterone reference ranges are even more lab-dependent — typically 50-200 pg/mL but check your specific lab's range.

When should I get my testosterone tested?

Between 7am and 10am, when testosterone naturally peaks in its circadian rhythm. Testing in the afternoon can show levels 20-30% lower than morning, which can make a normal man look hypogonadal. Always get bloodwork in the morning, ideally on two separate mornings before treating any abnormal result.

What other labs affect testosterone interpretation?

LH and FSH distinguish primary (testicular) from secondary (pituitary/hypothalamic) hypogonadism. Prolactin rules out a pituitary tumor. Estradiol matters because excess estrogen can mask or contribute to low-T symptoms. Vitamin D, ferritin, thyroid (TSH), and a metabolic panel are also useful context for interpreting borderline T results.

Education Published April 18, 2026

How to Read Your Testosterone Bloodwork: Total T, Free T, SHBG Explained

You asked your doctor for a testosterone test, the results came back, and now you're staring at a PDF full of numbers and abbreviations. Total T, free T, SHBG, bioavailable T. Here's what each one actually measures, what counts as normal, and why a lot of guys get waved off with results that deserve a second look.

Start With the Big Three

A decent testosterone panel has three numbers that matter: total testosterone, free testosterone, and SHBG (sex hormone-binding globulin). Some panels also include bioavailable testosterone and albumin. If your doctor only ordered total T, you're missing half the picture.

Total Testosterone

Total testosterone measures every testosterone molecule in your bloodstream, whether it's doing anything useful or not. It's reported in nanograms per deciliter (ng/dL) in the US, or nanomoles per liter (nmol/L) in most other countries. To convert: 1 nmol/L is roughly 28.8 ng/dL.

Here's the catch: most of your total testosterone is bound to proteins and biologically inactive. Roughly 40 to 50% is tightly bound to SHBG (useless to your tissues), another 45 to 55% is loosely bound to albumin, and only about 1 to 3% is truly free and floating around ready to act. The "free" plus "albumin-bound" fraction is called bioavailable testosterone, because albumin releases its grip easily.

So total T tells you the size of the tank. It does not tell you how much fuel is actually reaching the engine.

Free Testosterone

Free testosterone is the unbound fraction, the T that can actually enter cells and bind androgen receptors. This is the number that correlates most tightly with symptoms like low libido, fatigue, brain fog, and poor erections.

Two men can have the same total T (say, 500 ng/dL) and feel wildly different. One has low SHBG and plenty of free T. The other has sky-high SHBG that's locking most of it up, and his free T is in the basement. Symptoms follow free T, not total T.

Normal free testosterone reference ranges vary by lab and by assay method (more on that in a second), but a common adult male range is roughly 50 to 200 pg/mL or 9 to 30 ng/dL. Anything under about 6.5 ng/dL (65 pg/mL) is generally considered low.

A Warning About Free T Assays

Not all free T tests are created equal. The gold standard is equilibrium dialysis, often reported as "free T, direct." Most cheap panels use a calculated free T from total T, SHBG, and albumin, which is reasonably accurate. The one to avoid is the old "free T analog" immunoassay, which is notoriously unreliable and still shows up on some Quest and LabCorp panels. If your free T looks way off compared to your total T and SHBG, check which method was used.

SHBG: The Gatekeeper

SHBG (sex hormone-binding globulin) is a protein made in the liver that binds tightly to testosterone (and estrogen) in the blood. It's basically a sponge. High SHBG means more T gets soaked up and locked away. Low SHBG means more T stays free.

Normal male SHBG is usually 10 to 57 nmol/L, though optimal is probably in the 20 to 45 range. Things that push SHBG up: aging, hyperthyroidism, liver disease, chronic caloric restriction, heavy endurance training, some medications (anticonvulsants, estrogen). Things that push SHBG down: obesity, insulin resistance, type 2 diabetes, hypothyroidism, high-protein diets, androgen use.

Why it matters: if your total T is 450 ng/dL (borderline) and your SHBG is 70 nmol/L, your calculated free T is probably dismal and you will feel like garbage. If your total T is 450 and SHBG is 20, your free T is likely fine and you probably feel okay. Same total T, completely different story.

Reference Ranges by Age

Here's where things get messy. "Normal" reference ranges are built from the general population, including older and overweight men, so the bottom of the range is arguably too low. The Endocrine Society's 2018 guideline uses 300 ng/dL as the threshold for biochemical hypogonadism in adult men, and the American Urological Association (AUA) agrees with that cutoff.

Rough total testosterone ranges by decade, from pooled reference data:

20s: 400 to 1,080 ng/dL, average around 650
30s: 380 to 1,000 ng/dL, average around 600
40s: 350 to 890 ng/dL, average around 550
50s: 320 to 870 ng/dL, average around 500
60s+: 300 to 720 ng/dL, average around 430

Testosterone drops roughly 1 to 2% per year after 30. That's not an excuse, it's a baseline. For a deeper breakdown by decade see our article on testosterone levels by age.

What "Low," "Borderline," and "Optimal" Actually Mean

Low (under 300 ng/dL)

This is the Endocrine Society and AUA threshold for biochemical hypogonadism. If you have symptoms (low libido, erectile dysfunction, fatigue, depression, loss of muscle) and two morning fasting readings under 300, you meet the criteria for a clinical low T diagnosis. Worth a workup to find the cause (primary vs secondary hypogonadism).

Borderline (300 to 450 ng/dL)

This is the gray zone where most guys get dismissed. "You're in the normal range, nothing to do." Technically true. Practically, many men in this range feel symptomatic, especially if SHBG is elevated and free T is low. This is where you push for a free T, SHBG, LH, FSH, and estradiol panel instead of accepting "you're fine."

Optimal (500+ ng/dL with good free T)

Most men feel best with total T north of 500 and free T in the upper half of the range. Not a formal medical category, but a reasonable target for anyone who wants to feel good rather than just not qualify as sick.

Why Doctors Dismiss Borderline Results

Three reasons. First, the reference range includes the whole population, so being "in range" is the default bar. Second, insurance doesn't cover TRT for a 420 ng/dL result, so there's no actionable path for a standard PCP. Third, most general practitioners have 15 minutes per appointment and no specialized endocrinology training. If you're borderline and symptomatic, ask for a referral to a urologist or endocrinologist who focuses on men's hormonal health.

How to Draw Blood Correctly (Or Your Numbers Are Garbage)

Morning Only. Preferably Before 10am.

Testosterone follows a strong circadian rhythm, peaking between 7am and 10am and dropping 20 to 30% by afternoon. The Endocrine Society explicitly recommends drawing between 7am and 10am. An afternoon reading of 380 ng/dL could easily be a morning reading of 520. Do not let a lab draw you at 2pm and then tell you your T is low.

Fasted

A meal, particularly a high-carb meal, acutely lowers total testosterone by around 25% for a couple of hours. Most guidelines say fasted is ideal, though the effect is smaller than time of day. Either way: no breakfast before your draw.

Not After a Bad Night's Sleep

Even one night of short sleep (5 hours) can drop T by 10 to 15%. Don't draw the morning after a red-eye flight or a late night out. See our piece on sleep and testosterone for the full story.

Not Sick, Not Hungover, Not Post-Workout

Acute illness, alcohol within 24 hours, and recent heavy exercise all temporarily suppress testosterone. If you want a real baseline, draw on a normal day, not the Monday after a wedding weekend.

When to Re-Test

A single low or borderline reading is not a diagnosis. Both the Endocrine Society and AUA require two separate morning readings before diagnosing hypogonadism. If your first result is low or borderline, re-test in 2 to 4 weeks under the same conditions (same lab, same time, same fasting state). Variation of 15 to 20% between draws is normal.

If you're tracking progress after a lifestyle change (sleep fix, weight loss, strength training), give it at least 8 to 12 weeks before re-testing. Hormonal adaptations are slow.

What Else Should Be On the Panel

A complete hormonal workup for a symptomatic man should include:

Total testosterone (morning, fasted)
Free testosterone (equilibrium dialysis or calculated, not analog)
SHBG
LH and FSH (tells you if the problem is in the testes or the brain)
Estradiol (sensitive assay, not standard)
Prolactin (high prolactin suppresses T)
TSH and free T4 (thyroid affects SHBG and T)
Fasting glucose, insulin, HbA1c (metabolic health drives T)
Vitamin D, ferritin (both affect T)

If your doctor won't order these, services like Quest's direct-to-consumer panels, LabCorp On Demand, or Marek Health let you order them yourself for 100 to 300 dollars.

Quick Takeaways

Total T is the tank, free T is the fuel actually reaching cells. Free T correlates with how you feel.
SHBG decides how much of your total T is free. High SHBG can make a "normal" total T feel like low T.
Under 300 ng/dL is the Endocrine Society and AUA threshold for hypogonadism. 300 to 450 is the borderline zone where guys get dismissed.
Always draw morning (before 10am), fasted, rested. Afternoon draws are useless for diagnosis.
Never diagnose off one reading. Re-test 2 to 4 weeks later under the same conditions.

Not medical advice. If your labs are abnormal, see an endocrinologist or urologist.