Blood Tests on Testosterone Replacement Therapy
The complete TRT monitoring panel — testosterone levels, haematocrit, PSA, oestradiol, and lipids — with Australian reference ranges and a clear monitoring schedule.
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The Quick Answer
Testosterone replacement therapy (TRT) is increasingly prescribed for Australian men with confirmed hypogonadism — low testosterone with symptoms such as fatigue, low libido, mood changes, reduced muscle mass, and erectile dysfunction. Available forms in Australia include injections (Sustanon 250, Primoteston Depot, Reandron 1000), gels (Testogel, Axiron), and cream (compounded).
Regular blood monitoring is not optional — it is a condition of ongoing prescribing in Australia. The most critical safety test is haematocrit: testosterone stimulates red cell production and can thicken the blood to dangerous levels. Prostate monitoring (PSA) and hormonal balance (oestradiol, SHBG) are equally important for long-term safety and treatment optimisation.
How TRT Affects Your Blood Tests
Testosterone has receptors in almost every tissue. When you replace testosterone exogenously, you see changes across multiple systems that are visible in blood tests. Some changes are the intended therapeutic benefit (rising testosterone, improving HbA1c, falling triglycerides). Others are side effects that need monitoring (rising haematocrit, rising oestradiol, changing PSA).
The most important concept for TRT blood tests is trough timing. For injectable testosterone, your levels peak 24-48 hours after injection and fall to their lowest point (the trough) just before the next injection. Blood tests for hormone levels must always be taken at the trough to give a consistent, comparable reading. Testing at peak gives falsely high results and leads to unnecessary dose reductions.
For testosterone gels and creams, test first thing in the morning before applying the daily dose. For long-acting injections like Reandron 1000 (given every 10-14 weeks), the trough is typically 7-10 days before the next scheduled injection.
Key Blood Tests to Monitor on TRT
Australian reference ranges from RCPA guidelines and Endocrine Society of Australia recommendations. Therapeutic targets on TRT differ from population reference ranges — your prescriber will set your personal targets.
Total testosterone
Confirm you are in the therapeutic range. Time the blood test as a trough — just before your next injection or gel application. Peak levels (24-48h after injection) are less meaningful. Levels above 30 nmol/L at trough suggest the dose needs reducing.
Free testosterone
Active fraction not bound to SHBG or albumin. Useful when total testosterone looks normal but symptoms persist. Low SHBG (common in obesity, type 2 diabetes, metabolic syndrome) inflates free T relative to total T.
SHBG (sex hormone binding globulin)
Determines how much free testosterone is available. Low SHBG means more free testosterone available, which may cause haematocrit and oestradiol to rise faster. High SHBG may mean you need a higher total testosterone dose to achieve adequate free T levels.
Oestradiol (E2)
Monitor aromatisation of testosterone to oestrogen. Some oestradiol is beneficial — essential for bone density, libido, and cardiovascular health in men. Symptomatic high E2 (breast tenderness, water retention, emotional lability) with levels consistently above 250 pmol/L may need management.
Haematocrit and haemoglobin
Detect polycythaemia — the most serious TRT safety concern. Testosterone stimulates erythropoietin and red cell production. HCT above 0.54 significantly increases stroke and clotting risk. This test must be done every 3 months in the first year. If elevated: reduce dose, increase injection frequency (to reduce peak levels), or therapeutic venesection.
PSA (prostate-specific antigen)
Prostate cancer surveillance — mandatory before and during TRT. Baseline PSA is compulsory before starting TRT in all men over 40. A PSA rise of more than 1.4 ng/mL in 12 months, or more than 0.4 ng/mL in 6 months, warrants urgent urological referral regardless of absolute level.
LH and FSH
Confirm hypothalamic-pituitary axis suppression. On exogenous testosterone, LH and FSH should be suppressed to near-undetectable levels. Persistently elevated LH suggests the dose may be insufficient or the patient is not using their medication as prescribed.
Prolactin
Rule out prolactinoma as cause of low testosterone. Check at baseline to exclude a prolactinoma (pituitary adenoma) as the cause of hypogonadism. High prolactin causes low testosterone, low libido, and can cause gynaecomastia. Prolactinomas are treated with dopamine agonists, not TRT.
Lipid panel (total, LDL, HDL, triglycerides)
Testosterone can reduce HDL (the protective cholesterol). Testosterone, particularly oral and high-dose injectable forms, can reduce HDL cholesterol by 10-20%. Injectable testosterone has a milder effect on lipids than oral methyltestosterone (which is not used in Australia). Annual lipid monitoring is recommended.
HbA1c and fasting glucose
TRT improves insulin sensitivity in hypogonadal men. Hypogonadism is associated with metabolic syndrome and type 2 diabetes. TRT often improves insulin sensitivity and HbA1c over 6-12 months as muscle mass and body composition improve. Useful to track the metabolic benefits of treatment.
Full blood count (FBC)
Complete picture beyond haematocrit alone. Includes haematocrit, haemoglobin, red cell count, and white cell count. The full picture helps differentiate polycythaemia from other causes of a high haematocrit such as dehydration or lung disease.
Side Effects and Their Blood Test Links
Understanding which symptoms correspond to which blood test abnormalities helps you have a more productive conversation with your prescribing doctor.
Polycythaemia (thick blood)
The most serious TRT risk. Haematocrit above 0.54 significantly increases the risk of stroke, DVT, and pulmonary embolism. Must be monitored every 3 months in the first year. Managed by reducing dose, increasing injection frequency, or therapeutic venesection.
Acne and oily skin
Testosterone stimulates sebaceous glands. Common in the first 3-6 months, especially when doses are supraphysiological. Usually improves with dose reduction or gel formulation (steadier levels). Topical retinoids or antibiotics can help if severe.
Testicular atrophy
The testes produce testosterone themselves. When exogenous testosterone suppresses LH and FSH, the testes receive no stimulus and shrink over months. This is expected and does not affect sexual function, but does affect fertility. hCG co-administration can preserve testicular size and some fertility.
Gynaecomastia (breast tissue)
Caused by high oestradiol from aromatisation of testosterone, or from a high oestradiol-to-testosterone ratio. Tender breast tissue under the nipple is the classic presentation. Oestradiol level and dose adjustment should be checked. Rarely requires surgical management.
Mood changes and aggression
Supraphysiological testosterone levels (well above the normal range) can cause irritability, mood swings, and in some men increased aggression. Trough levels consistently above 30 nmol/L should prompt dose review. Low oestradiol can also cause mood depression in men on TRT.
Sleep apnoea worsening
Testosterone can worsen obstructive sleep apnoea. If you snore loudly, wake feeling unrefreshed, or your partner notices breathing pauses during sleep, seek assessment. Untreated sleep apnoea also raises haematocrit independently of TRT.
Red Flags — When to Seek Urgent Help
These findings or symptoms require same-day or emergency review — do not wait for your routine follow-up appointment:
Haematocrit above 0.54 (54%)
This is a hard stop. At this level, blood is dangerously viscous and the risk of stroke, pulmonary embolism, and deep vein thrombosis is substantially elevated. TRT should be paused and therapeutic venesection considered. Do not delay.
Leg pain, calf swelling, or redness
Classic signs of deep vein thrombosis (DVT). Go to emergency. TRT-associated polycythaemia significantly raises DVT risk. You will need an urgent D-dimer, Doppler ultrasound, and anticoagulation assessment.
Sudden shortness of breath or chest pain
May indicate pulmonary embolism from a dislodged DVT. This is a medical emergency. Call 000 immediately. Do not drive yourself to hospital.
Rapidly rising PSA
A rise of more than 1.4 ng/mL in 12 months, or more than 0.4 ng/mL in any 6-month period, warrants urgent urological referral. Do not wait for your next routine appointment.
Severe mood disturbance or aggression
Supraphysiological testosterone or very low oestradiol can both cause significant mood disturbance. Check trough testosterone, oestradiol, and consider dose reduction. Seek GP review urgently if mood changes are severe or putting relationships at risk.
Persistent testicular pain or new lump
Testicular atrophy on TRT is expected, but pain or a new lump in the testes warrants urgent scrotal ultrasound to exclude testicular cancer, which is unrelated to TRT but affects the same age group.
TRT Monitoring Schedule
Based on Endocrine Society of Australia and Urological Society of Australia guidelines. Your GP or endocrinologist may adjust this schedule based on your individual risk profile.
Baseline before starting TRT
Full hormone panel (two early morning total testosterone, LH, FSH, prolactin, SHBG, oestradiol), full blood count, lipid panel, HbA1c, LFTs, kidney function, and PSA. Two low testosterone readings on separate mornings are required to diagnose hypogonadism in Australia.
Six weeks after starting (trough level)
Total testosterone, free testosterone, haematocrit, and haemoglobin. This confirms you are in the therapeutic range and checks for early polycythaemia. Time the test as a trough: immediately before your next injection, or first thing in the morning for daily gels.
Three months (full safety panel)
Full panel: testosterone trough and free T, oestradiol, haematocrit, FBC, PSA, lipid panel, LFTs. This is the critical safety checkpoint. Dose adjustments are commonly made based on trough levels, haematocrit, and PSA at this visit.
Six months
Testosterone trough, haematocrit, PSA, oestradiol. Focus on safety. If all stable and within target ranges, discuss with your doctor whether 6-monthly monitoring is appropriate going forward.
Annually (comprehensive)
Full panel including lipids, HbA1c, LFTs, kidney function, FBC, PSA, testosterone, oestradiol, SHBG. Annual digital rectal examination and PSA interpretation per urology guidance. Review whether TRT is still indicated and whether the dose remains appropriate.
After any dose change
Restart the 6-week trough check after any dose adjustment. Haematocrit should be re-checked at 3 months after any change that increases the dose. PSA should be re-checked at 3-6 months after dose changes.
Lifestyle Strategies to Optimise TRT Safety
Donate blood or therapeutic venesection
SafetyIf haematocrit is rising towards 0.52-0.53, regular blood donation (if eligible) can help keep it in range. Australian Red Cross accepts donors from people on TRT. Therapeutic venesection can be arranged through your GP or haematologist if donation is not possible.
Resistance training
ExerciseTRT and resistance exercise have a synergistic effect on lean muscle mass. 3-4 sessions per week of compound lifts (squats, deadlifts, rows, presses) maximises the body composition benefits of treatment and improves insulin sensitivity.
Maintain a healthy body weight
MetabolicBody fat contains aromatase enzyme, which converts testosterone to oestradiol. Reducing body fat lowers oestradiol, reduces SHBG, and often allows lower TRT doses to achieve the same free testosterone levels.
Sleep apnoea screening and treatment
SafetyUntreated obstructive sleep apnoea independently raises haematocrit and erythropoietin. If you are snoring or waking unrefreshed, get a sleep study. CPAP treatment reduces haematocrit and also improves testosterone levels naturally.
Alcohol moderation
LifestyleAlcohol increases oestradiol levels (by inhibiting aromatase clearance), raises triglycerides, reduces testosterone, and impairs recovery from exercise. Reducing alcohol to below NHMRC guidelines helps optimise your hormonal environment.
Stay well hydrated
SafetyDehydration concentrates the blood and can artificially elevate haematocrit readings. Ensure adequate daily fluid intake especially in summer or after exercise before having your blood test, and note this to your GP if haematocrit is borderline.
Sources and reference ranges
Adult reference ranges on this page follow the AACB and RCPA harmonised reference intervals unless stated otherwise; the range printed on your own report always takes precedence because laboratories differ.
Blood Tests on Testosterone Replacement Therapy (TRT) — Frequently Asked Questions
What blood tests do I need on TRT?
The core TRT monitoring panel includes: total testosterone and free testosterone (to confirm you are in the therapeutic range), oestradiol (E2, because testosterone converts to oestrogen), haematocrit and haemoglobin (to detect dangerous blood thickening), PSA (prostate-specific antigen, for prostate cancer screening), SHBG (sex hormone binding globulin), LH and FSH (suppressed on TRT, confirming axis shut-down), full lipid panel, and HbA1c. In Australia most GPs also check LFTs and kidney function annually.
How often should I have blood tests on TRT?
Australian Endocrine Society guidelines recommend: baseline before starting, repeat at 6 weeks (first trough level check), then at 3 months (full panel including haematocrit and PSA), then 6-monthly for the first year, then every 6-12 months once stable. Haematocrit must be checked every 3 months in the first year. If your dose is changed, restart the 6-week trough check.
What is a dangerous haematocrit level on TRT?
A haematocrit above 0.54 (54%) is considered dangerous and typically triggers a pause in TRT or a therapeutic venesection (blood donation or therapeutic bleed). Above this level, blood viscosity increases the risk of stroke, deep vein thrombosis (DVT), and pulmonary embolism. Most Australian clinicians aim to keep haematocrit below 0.50-0.52. Report symptoms of blood clots (leg pain and swelling, shortness of breath, chest pain) urgently.
What testosterone level should I aim for on TRT?
Most Australian endocrinologists aim for a trough testosterone (just before your next injection or application) in the mid-normal adult male range: roughly 15-25 nmol/L for injections, or 10-20 nmol/L for gels. Peak levels (24-48 hours after a Sustanon or testosterone enanthate injection) can reach 40-50 nmol/L and are less clinically meaningful than the trough. Levels above 30 nmol/L at trough suggest the dose is too high.
Does TRT cause high oestrogen and do I need to treat it?
Testosterone aromatises (converts) to oestradiol (E2) in fat tissue, so oestradiol often rises on TRT. Mildly elevated oestradiol is normal and may even be beneficial for bone density, libido, and mood. Symptomatic high oestradiol (nipple tenderness, water retention, mood swings) with a level consistently above 200-250 pmol/L may warrant discussion of an aromatase inhibitor with your prescribing doctor. Do not use AI drugs without medical supervision.
Does TRT increase prostate cancer risk?
Current evidence suggests TRT does not cause prostate cancer, but it can stimulate growth of pre-existing prostate cancer. A baseline PSA before starting TRT is mandatory in all men over 40 in Australia. PSA should be repeated at 3 months and then annually. A rapidly rising PSA (more than 1.4 ng/mL rise in 12 months, or a rise of 0.4 ng/mL in 6 months) warrants urological referral regardless of the absolute value.
Will TRT make me infertile?
Yes, TRT suppresses your own testosterone production by shutting down the hypothalamic-pituitary-gonadal axis. This drastically reduces sperm production and can cause infertility. LH and FSH will be suppressed to near-zero on TRT. If fertility is important to you, discuss alternatives with your urologist — options include hCG (human chorionic gonadotrophin) injections, which stimulate the testes directly while preserving some sperm production.
Related Reading
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This page provides general educational information about TRT blood test monitoring. It is not a substitute for professional medical advice. TRT requires a valid prescription and ongoing medical supervision in Australia. Always consult your prescribing doctor about your individual monitoring schedule and results. SmarterBlood does not provide medical care.