Starting TRT isn't a one-off blood test followed by a prescription. Done properly, it involves a structured baseline panel, a confirmation blood test at least two weeks later, then ongoing monitoring throughout treatment. Here's what each test means and why it matters.
Before Starting TRT: The Baseline Panel
| Test | What It Shows | Why It's Needed |
|---|---|---|
| Total testosterone (8–11am, fasted) | Your circulating testosterone level | Diagnosis — must be low on two separate tests to confirm hypogonadism |
| SHBG | Binding protein that determines free fraction | High SHBG can suppress free T despite normal total T |
| Free testosterone (calculated) | Biologically active fraction | The number that correlates with symptoms |
| LH + FSH | Pituitary signalling hormones | Low LH + low T = secondary hypogonadism (pituitary origin); high LH + low T = primary (testicular) |
| Oestradiol | Oestrogen level | Baseline before treatment; guides aromatase inhibitor need during TRT |
| Prolactin | Pituitary hormone | High prolactin suppresses LH and testosterone — must exclude before starting TRT |
| Full blood count (FBC) | Haemoglobin, haematocrit, red cell count | TRT increases red cell production — baseline haematocrit needed |
| PSA | Prostate specific antigen | Contraindication check — TRT is not initiated with elevated PSA |
| Liver function tests (LFTs) | Liver enzyme panel | Baseline safety check, particularly relevant for oral testosterone |
| Lipid profile | Cholesterol panel | TRT affects HDL — baseline allows monitoring of cardiovascular risk |
| HbA1c + glucose | Blood sugar | TRT improves insulin sensitivity — important baseline for diabetic patients |
| Thyroid (TSH) | Thyroid function | Hypothyroidism causes similar symptoms and must be excluded |
During TRT: What to Monitor and How Often
Once treatment is established, monitoring is required at regular intervals:
| Test | Frequency | What to Watch For |
|---|---|---|
| Total + free testosterone | 6 weeks after starting; then 3–6 monthly | Target: total T 15–25 nmol/L (trough for injections) |
| Haematocrit (Hct) | 3–6 monthly | Hct >54%: TRT dose reduction or dose interval adjustment needed |
| Oestradiol | 6 weeks; then 6 monthly | Elevations cause water retention, gynaecomastia, mood changes |
| PSA | Annually (over 45); 3 monthly initially if baseline was borderline | Rise >1.4 ng/mL over 12 months warrants urology referral |
| LFTs | 6 monthly | Usually stable on injectable; more relevant with gel or oral forms |
| Lipids | Annually | TRT can lower HDL — monitor cardiovascular risk markers |
| Full blood count | 6 monthly | Tracks haemoglobin rise and confirms haematocrit within safe limits |
When to Test: Trough vs Midpoint
For injectable testosterone, always test at trough — immediately before your next injection is due. This gives the lowest point of your cycle and confirms that your levels are therapeutic rather than excessive. Testing at peak (day 2–3 post-injection) will give a misleadingly high result and risks dose increases that aren't needed.
TRT Monitoring at Lambert Medical Practice
Our TRT clinic manages your full monitoring schedule — baseline, 6-week review, and ongoing tests — with same-week results and GP interpretation.
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