TRT Blood Test: How to Read Your Results
Deciphering the numbers behind your hormonal health. A comprehensive guide to understanding Testosterone, SHBG, Free T, and safety markers in Australian pathology reports.
Note: Reference ranges vary by lab. This guide uses standard Australian units (nmol/L & pmol/L).
Check Your Eligibility for TRT Consultation
Answer 8 questions to see if you meet the basic criteria for a medical assessment. This is not a diagnosis.
What is your age?
TRT consultation requires minimum age criteria
Have you noticed changes in energy levels?
Common concern for men considering consultation
What about changes in body composition?
Physical changes despite consistent lifestyle
Changes in libido or sexual function?
Common concern prompting medical consultation
Mood or cognitive changes?
Brain fog, irritability, or low mood
Do you have any of these conditions?
Medical contraindications that may affect eligibility
Have you had testosterone levels tested before?
Previous blood work can streamline assessment
What’s your main goal for seeking consultation?
Understanding your consultation priorities
The “Reference Range” Dilemma
Why “Normal” doesn’t always mean “Optimal” or “Healthy”.
📊 The Curve is Not Your Friend
Most pathology labs in Australia calculate reference ranges based on a statistical average of the population they test—often including men who are elderly, sick, or obese. Being “in range” (e.g., the bottom 5%) means you are statistically “normal” compared to that group, but you may still be clinically symptomatic.
Key Takeaway: We treat patients, not just numbers. A result of 9.0 nmol/L might be “in range” for some labs, but potentially symptomatic for a 35-year-old male.
1. The Core Hormones
The primary markers used to assess androgen status.
Total Testosterone (TT)
Unit: nmol/L (Nanomoles per Litre)
This is the total amount of testosterone floating in your blood. However, it is a broad overview, not the full story.
- Australian Range: Typically 8.0 – 28.0 nmol/L (varies by lab).
- What it misses: It does not tell us how much hormone is actually available for your body to use (see Free T).
SHBG
Sex Hormone Binding Globulin
Think of SHBG as a “bus” that picks up testosterone. When T is on the bus, it cannot enter cells to do its job.
- High SHBG: Locks up testosterone, leading to low Free T even if Total T is normal. Common in aging, liver stress, or extreme diets.
- Low SHBG: T is metabolized too quickly. Common in obesity/insulin resistance.
Free Testosterone (cFT)
Unit: pmol/L (Picomoles per Litre)
This is the “active” fuel. It represents the ~2-3% of testosterone that is unbound and able to enter cells to build muscle, affect mood, and drive libido.
- Calculated vs Measured: Often calculated using Total T, SHBG, and Albumin (Vermeulen formula) for higher accuracy than direct testing.
- Symptom Driver: Low Free T correlates most strongly with TRT symptoms.
2. The Control Signals (Brain-Testes Loop)
Determining why levels are low: Primary vs. Secondary Hypogonadism.
Low LH + Low T: “Secondary Hypogonadism”. The brain isn’t sending the signal. Common in stress, sleep apnea, or pituitary issues.
On TRT: LH and FSH typically drop to near zero, as the body senses external testosterone and stops its own production signals.
3. Safety & Health Markers
Essential checks before and during therapy to ensure systemic health.
High: Water retention, emotional sensitivity, gynecomastia (“gyno”).
Low: Aching joints, osteoporosis, zero libido.
TRT does not cause prostate cancer, but if cancer is already present, TRT can stimulate it. Essential baseline check for men over 40-45.
Testosterone stimulates red blood cell production. If blood becomes too thick (High HCT), therapeutic phlebotomy (blood donation) or dose adjustment may be required.
Very High: Can indicate a Prolactinoma (benign pituitary tumor) which suppresses testosterone. Can also be elevated by stress or certain medications.
It is crucial to rule out thyroid dysfunction (Hypothyroidism) before assuming Testosterone is the culprit.
Baseline metabolic health. Poor liver function can elevate SHBG. Metabolic syndrome (high triglycerides, low HDL) often accompanies low testosterone.
Ensuring Accurate Results
Bad preparation leads to false diagnoses. Follow this protocol for accuracy.
The 7am – 10am Window
Testosterone levels follow a circadian rhythm, peaking in the early morning and dropping significantly by afternoon. Afternoon tests can show falsely low levels (sometimes 30% lower).
Rule: Always draw blood between 7:00 am and 10:00 am.
Fasted vs. Fed
Eating, particularly glucose/carbohydrates, can acutely lower testosterone levels for hours. High fat meals can interfere with lipid testing.
Rule: Fast for 8-12 hours prior to the draw. Water is fine and encouraged for hydration (makes drawing blood easier).
The Biotin Interference
Biotin (Vitamin B7), often found in multivitamins and hair/skin supplements, interferes with the lab assays for hormones, potentially causing falsely high Testosterone and falsely low TSH.
Rule: Stop any Biotin-containing supplements 3-5 days before your blood test.
Avoid Acute Illness
Testing while you have the flu, a fever, or immediately after extreme endurance events can temporarily crash testosterone levels.
Rule: Wait until you are fully recovered from acute illness before testing.
Common Result Profiles
Do any of these look like you?
The “Classic” Low T
- 🔻 Total T: Low (< 8-10 nmol/L)
- 🔻 Free T: Low (< 250 pmol/L)
- ↔️ SHBG: Normal
Classic deficiency. Requires investigation into LH/FSH to determine if the cause is testicular (primary) or pituitary (secondary).
The “High SHBG” Trap
- ✅ Total T: Normal/High
- 🔻 Free T: Low
- 🔺 SHBG: Very High (> 50 nmol/L)
Total T looks great, but the patient feels terrible. The SHBG is binding all the testosterone, leaving nothing active. Common in aging, hyperthyroidism, or keto/carnivore diets.
The “Metabolic” Profile
- 🔻 Total T: Low/Borderline
- 🔻 SHBG: Very Low
- 🔻 LH: Low/Normal
Often seen in men with high body fat or insulin resistance. The body clears T rapidly due to low SHBG. Weight loss is often the first line of treatment here.
Frequently Asked Questions
What is the difference between nmol/L and ng/dL?
These are different units of measurement. Australia uses nmol/L (molar units), while the USA uses ng/dL (mass units).
Conversion: 1 nmol/L ≈ 28.85 ng/dL.
Example: A result of 10 nmol/L in Australia is roughly 288 ng/dL in US terms.
My Doctor says my levels are “Normal” but I have symptoms. Why?
“Normal” is a statistical range, not a biological switch for health. If you are at the very bottom of the range (e.g., 9.0 nmol/L) and have symptoms, you may have “functional hypogonadism.” Many general practitioners are hesitant to treat borderline cases. Specialist TRT clinics assess the full clinical picture—symptoms plus bloods—rather than relying on a single number.
Why do I need to test Haematocrit/Haemoglobin?
Testosterone increases red blood cell production (erythropoiesis). If this goes unchecked, blood can become viscous (thick), increasing cardiovascular strain. This is a critical safety marker that must be monitored on TRT.
Can I just test Testosterone and nothing else?
No. Testing only Total Testosterone is like looking at the fuel gauge of a car without checking the engine (Free T), the oil (E2), or the tires (PSA/HCT). You cannot make a safe or accurate medical decision based on Total Testosterone alone.
What is a “Calculated” Free Testosterone?
Directly measuring Free T in a lab is technically difficult and often inaccurate. Most specialists prefer “Calculated Free Testosterone” (cFT), which uses your Total T, SHBG, and Albumin results to mathematically determine the amount of unbound testosterone. This is considered the gold standard for clinical assessment.
Need a Professional Analysis?
If your results are confusing or you suspect low testosterone, take our eligibility assessment to see if a consultation is right for you.
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