The bloods you actually need before starting TRT

The online-TRT market has normalised starting testosterone based on one or two numbers. In a proper assessment, the blood panel is longer, the interpretation is richer, and the decision whether to treat is better calibrated. This article lists every test that should be done before the first TRT prescription and why each one matters.

Two morning testosterone measurements

Done between 7 and 10 AM, fasted, on two separate days. This is the single most important rule. Evening readings are routinely misleading and single readings miss day-to-day variability. Two morning readings below 8 nmol/L with symptoms is definite; both between 8 and 12 with symptoms and consistent other markers is probable; both above 12 is usually not hypogonadism regardless of symptoms.

If the two readings disagree significantly (one low, one normal), we repeat. Biological variability can be over 20 percent day to day.

SHBG

Sex hormone binding globulin. Rises with age, thyroid overactivity, liver disease, anticonvulsants, oestrogens. Falls with obesity, insulin resistance, diabetes, hypothyroidism. Needed to calculate free testosterone, which is what matters biologically.

Free testosterone (calculated)

The fraction of testosterone that is not bound and can act on target tissues. Calculated from total T, SHBG, and albumin via the Vermeulen equation. A man with total T of 11 and high SHBG may have free T well below the reference range and is appropriately diagnosed as hypogonadal, while a man with the same total T but normal SHBG is not.

LH and FSH

Pituitary gonadotrophins. Distinguish primary (testicular, LH/FSH high) from secondary (pituitary, LH/FSH low) hypogonadism. The distinction changes investigation and management. Primary hypogonadism is the testes' problem; secondary is usually obesity, opioid, or less commonly a pituitary cause.

Oestradiol (E2)

Testosterone is aromatised into oestradiol in fat tissue. Baseline E2 is needed before TRT so we can track the rise and intervene if it climbs significantly. Heavier men with more adipose tissue aromatise more; some of them need an aromatase inhibitor (anastrozole low dose) if E2 rises disproportionately.

Prolactin

Catches the rare but important prolactinoma. Significantly elevated prolactin (usually over 1000 mIU/L, though context matters) triggers pituitary MRI. Missing a prolactinoma means treating the hypogonadism symptom while the tumour grows.

PSA (prostate-specific antigen)

Baseline is mandatory for men over 45 starting TRT and strongly advisable for men over 40. TRT does not cause prostate cancer but can accelerate an existing subclinical cancer. We need a baseline to interpret future changes. PSA above 4 ng/mL usually triggers urology referral before TRT. PSA 2.5 to 4 ng/mL in a man over 55 is also a trigger for specialist review.

Full blood count with haematocrit

TRT raises red cell count reliably. Haematocrit above 0.52 is a concern on TRT; above 0.54 usually prompts dose reduction or therapeutic venesection. Baseline haematocrit is needed to track change. A baseline already at 0.51 needs a slower titration and closer monitoring than one at 0.44.

Urea, electrolytes, creatinine, eGFR

Kidney function. Relevant because kidney disease affects hormone clearance and monitoring frequency. Rarely abnormal but worth a baseline.

Liver function tests

Baseline ALT, AST, GGT, alkaline phosphatase, bilirubin. Oral testosterone (undecanoate, rarely used) is hepatotoxic. Injectable and transdermal forms do not cause liver injury reliably, but baseline matters for interpretation of subsequent changes.

TSH (and T4 if indicated)

Thyroid disease overlaps clinically with hypogonadism. Hypothyroidism causes fatigue, weight gain, low libido, low mood. Treating missed hypothyroidism with TRT instead of levothyroxine is a classic error. TSH is included in every panel we run.

HbA1c and fasting glucose

Diabetes and prediabetes are both associated with secondary hypogonadism. Treating the metabolic picture often raises testosterone. Baseline HbA1c is also needed to track the modest improvement that TRT typically produces in insulin sensitivity.

Lipids

Total cholesterol, LDL, HDL, triglycerides, and increasingly ApoB. TRT modestly reduces LDL and raises HDL in hypogonadal men. Baseline is needed for interpretation and for cardiovascular risk assessment.

Vitamin D, B12, folate, ferritin

Deficiencies in any of these produce fatigue, cognitive symptoms, or mood effects that look like hypogonadism. Iron deficiency without anaemia is particularly commonly missed. Supplementing these corrects many complaints without TRT.

hs-CRP

Marker of low-grade inflammation. Elevated in metabolic disease, untreated apnoea, and active chronic illness. Useful for cardiovascular risk stratification.

Optional: pituitary-focused tests if suspicion

ACTH, morning cortisol, IGF-1, and free T4 are added if secondary hypogonadism looks likely from the initial pattern (low T with low LH/FSH). A pattern suggestive of panhypopituitarism triggers pituitary MRI and endocrinology referral.

Why a single testosterone test is insufficient

Even with a correctly taken morning reading, a single testosterone test alone does not distinguish:

- Primary vs secondary hypogonadism (needs LH/FSH) - Reversible vs irreversible causes (needs prolactin, SHBG, context) - Whether the treatment should be TRT or weight loss or apnoea treatment (needs metabolic screen, sleep history) - What baseline haematocrit is (needs FBC) - Whether prostate concern exists (needs PSA) - Whether thyroid is the actual issue (needs TSH)

A man started on TRT without these tests is being treated on incomplete information. The risks include missing a tumour, missing thyroid disease, starting treatment for the wrong condition, and running a long-term regimen without the ability to track change.

What LoveMyLife includes

Every assessment tier at LoveMyLife includes the full male hormone panel (total T, SHBG, calculated free T, LH, FSH, E2, prolactin), full metabolic panel (HbA1c, lipids including ApoB, liver function, renal function), FBC with haematocrit, PSA, TSH, and vitamin D / B12 / folate / ferritin. No separate blood charges. Results are interpreted by a GP and reviewed by our endocrinology consultant on any complex case.

The honest bottom line

A proper baseline is not about running every test available. It is about running the specific tests that change the management decision. Anyone offering TRT on less than the above is skipping information that matters. This is the difference between a prescription-mill and a clinician-led service.

Ready to start?

If this article has made you think an assessment might help, the next step is a short consultation with one of our men's health doctors.

Begin your consultation at this link. Online or in person at Westfield London.