Blood work is not optional on TRT — it is how you know whether the therapy is working, whether it is safe to continue, and whether anything needs adjusting. This is a complete guide to which panels to run, when to run them, and what each marker tells you.
Testosterone replacement changes multiple biological systems simultaneously. It affects haematocrit (red blood cell production), oestradiol levels (through aromatisation), lipid profiles, liver enzymes, and the HPT axis. Running TRT without monitoring is equivalent to taking any potent prescription medication without follow-up — possible, but not advisable.
The monitoring protocol exists not because TRT is inherently dangerous but because individual responses vary significantly. Some men aromatise testosterone to oestradiol aggressively. Some have haematocrit responses that require dosage adjustment. Some develop erythrocytosis. These are all manageable — but only if identified through regular testing.
Before beginning TRT, the following baseline measurements are essential:
Total testosterone (morning, fasted) — your starting point for everything. LH and FSH — establishes whether hypogonadism is primary or secondary and provides baseline. SHBG — determines free testosterone calculation. Oestradiol (sensitive assay) — baseline aromatisation rate. Full blood count including haematocrit — critical safety baseline. PSA (prostate-specific antigen, males over 40) — safety screen. Metabolic panel including liver enzymes. Thyroid panel — to rule out thyroid as cause of symptoms. Lipid panel.
Weeks 6-8: First follow-up. Total testosterone (trough — test just before next injection for injections, or any time for gels), haematocrit, oestradiol. This confirms whether the dose is achieving target levels and flags early haematocrit rise.
Months 3-4: Comprehensive panel. Repeat full baseline minus LH/FSH. Assess whether dose needs adjustment based on levels, symptoms and haematocrit.
Every 6 months thereafter: Full monitoring panel. Once stable, monitoring can often move to annual for haematocrit if levels have been consistently normal.
PSA: Annually for men over 40 on TRT.
Target total testosterone on TRT varies by individual response and symptoms but is typically 15-30 nmol/L for injections (measured at trough). Higher is not necessarily better.
Oestradiol: Should remain in range (typically 100-180 pmol/L on sensitive assay). High oestradiol causes water retention, mood changes and reduced libido. Low oestradiol (from over-use of aromatase inhibitors) causes joint pain, low mood and reduced bone density.
Haematocrit: Should remain below 54%. Above this level, blood viscosity increases significantly and cardiovascular risk rises. Haematocrit above 52% warrants dose reduction or therapeutic phlebotomy consideration.
SHBG: Affects how much testosterone is free and bioavailable. Low SHBG men often do better with more frequent, smaller injections. High SHBG men may need higher total testosterone to achieve adequate free testosterone.
Private blood testing without a GP referral is available across the UK. Most providers offer TRT-specific panels. Pricing varies — expect to pay £80-200 for a comprehensive panel depending on provider and number of markers. Testing at a clinic draw is preferable to home finger-prick for hormonal panels, particularly oestradiol, which is sensitive to collection method.
Many private TRT clinics include monitoring bloods as part of their service package. If self-managing, budgeting for quarterly testing is reasonable.
The full TRT blood work calendar — showing exactly when to test and what each marker should confirm at each point — is available inside the platform. The TRT Companion Protocol entry covers the complete monitoring schedule alongside the peptide additions used by men on TRT to support long-term health during therapy.
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Full TRT blood work calendar, gonadorelin protocol and peptide companion guide — available to members.