What Blood Tests You Actually Need Before Starting TRT

The Test That Gets Ordered Wrong Most Often

Ask any primary care clinician how they screen for low testosterone and the answer is almost always "I order a total testosterone." Ask when, and the answer too often includes "whenever the patient comes in." Ask whether they also check LH, and you usually get a blank stare.

This is how men get misdiagnosed — or correctly diagnosed for the wrong reason. Testosterone varies by time of day, by SHBG, by recent illness, and by whether you slept the night before. A single number, without context, is almost meaningless.

Here's what a legitimate workup actually looks like.

The Core Panel

Every defensible TRT workup should include these, at minimum:

1. Total Testosterone (×2)

The headline number. Measured between 7-10 a.m. Two readings on separate days are required per Endocrine Society guidelines. A single low reading is not a diagnosis.

Typical reference range: 300-1000 ng/dL (adult males)

Clinical hypogonadism threshold: two morning readings below 300 ng/dL

2. Free Testosterone

The bioavailable fraction — the testosterone not bound to SHBG or albumin. This is what actually acts on your tissues. Can be measured directly (equilibrium dialysis is the gold standard, usually only available at reference labs) or calculated from total T + SHBG + albumin.

Typical reference range: 5-21 ng/dL (varies by assay)

3. SHBG (Sex Hormone-Binding Globulin)

The protein that binds testosterone in blood, making it inactive. High SHBG reduces free T; low SHBG increases it. Important because total T alone can be misleading in both directions.

Typical reference range: 10-80 nmol/L

• High SHBG causes: aging, hyperthyroidism, liver disease, oral estrogens, cirrhosis
• Low SHBG causes: obesity, insulin resistance, type 2 diabetes, hypothyroidism

4. LH (Luteinizing Hormone)

The pituitary signal that tells the testes to make testosterone. This is the single most important test after total T.

• High LH + low T = primary hypogonadism (testicular problem; rare but changes the treatment conversation)
• Low or inappropriately normal LH + low T = secondary hypogonadism (pituitary/hypothalamic problem; the most common form, and the form that responds well to SERMs like enclomiphene)

5. FSH (Follicle-Stimulating Hormone)

The other pituitary signal, primarily relevant for spermatogenesis. Usually moves with LH; when it doesn't (FSH elevated, LH normal), it can suggest selective testicular damage.

6. Estradiol (Sensitive Assay)

Estradiol matters in men too — it's involved in bone, mood, libido, and sleep. Must be ordered as a "sensitive" or "ultra-sensitive" assay (LC-MS/MS); the standard immunoassay is unreliable at male-range concentrations.

Typical target on TRT: 20-40 pg/mL

Too high: emotional lability, nipple sensitivity, water retention

Too low: joint pain, low libido, poor sleep

7. Prolactin

Rules out pituitary adenoma (prolactinoma), which can suppress gonadotropins and cause secondary hypogonadism. Dramatic elevation (>100 ng/mL) warrants pituitary MRI.

8. TSH (and Free T4 if TSH is abnormal)

Thyroid dysfunction mimics low testosterone (fatigue, weight gain, mood changes). Must be ruled out before attributing symptoms to hormones.

9. Complete Blood Count (CBC)

Baseline for future monitoring, especially hematocrit — TRT commonly raises hematocrit and elevated values are the most common reason for dose adjustment.

Hematocrit caution zone on TRT: >52%

Action threshold: >54%

10. Comprehensive Metabolic Panel (CMP)

Screens for kidney, liver, and glucose abnormalities. Establishes baseline before starting a medication that touches all three systems.

11. PSA (if age 40+ or family history of prostate cancer)

TRT doesn't cause prostate cancer, but it can accelerate growth of an existing one. Baseline PSA is non-negotiable above 40. PSA velocity matters more than absolute value for monitoring.

Optional But Useful Additions

These are worth adding if budget allows or if clinical context points to them:

• A1C — long-term glucose control; insulin resistance is a common cause of low T
• Lipid panel — baseline for cardiovascular monitoring
• Vitamin D (25-OH) — deficiency is an independent driver of low T
• Ferritin — picks up hemochromatosis and iron-deficiency anemia
• IGF-1 — growth hormone status; low in some forms of hypopituitarism
• Cortisol (AM) — rules out adrenal insufficiency when fatigue is severe
• Urine metanephrines — only if clinical context suggests pheochromocytoma

What a Normal Lab Report Actually Looks Like

A 35-year-old man with clear low T might see:

• Total testosterone (AM): 248 → 262 ng/dL (two draws) — low
• Free testosterone: 5.2 ng/dL — low
• SHBG: 38 nmol/L — normal
• LH: 3.1 IU/L — inappropriately normal (should be high if primary)
• FSH: 2.8 IU/L — inappropriately normal
• Estradiol: 18 pg/mL — low
• Prolactin: 8 ng/mL — normal
• TSH: 2.1 — normal
• Hematocrit: 44% — normal
• PSA: 0.8 ng/mL — normal (for age)

Interpretation: secondary hypogonadism (LH/FSH inappropriately low for the T level). Good candidate for enclomiphene trial before committing to TRT.

Compare to a 60-year-old with the same total T:

• Total testosterone: 260 ng/dL
• LH: 12.4 IU/L — elevated
• FSH: 14.8 IU/L — elevated

Interpretation: primary (testicular) hypogonadism. SERMs won't help. TRT is the primary treatment option.

Same number, completely different treatment path. That's why LH and FSH matter.

Common Mistakes and Red Flags

• Afternoon blood draws — automatically low. Always morning.
• Single reading diagnosis — get two.
• Skipping LH/FSH — corner-cutting.
• Immunoassay estradiol — unreliable in men; demand LC-MS/MS.
• Clinics that prescribe without bloodwork — actively dangerous.
• "My T is 850 but I feel bad" — look at free T and SHBG; you may have normal total but low free.
• "My T is 380 but my SHBG is 12" — you probably have low free T despite the "normal" total.

What to Do With Borderline Results

Total T between 300 and 400 with symptoms is the most common — and most difficult — zone. The calculus:

• 3+ persistent symptoms + borderline T: treatment is defensible
• 1-2 symptoms + borderline T: repeat panel in 3 months, attempt lifestyle first (weight, sleep, training, alcohol reduction)
• Asymptomatic + borderline T: no intervention; recheck annually

A doctor who prescribes TRT to an asymptomatic man with T of 380 isn't practicing evidence-based medicine. A doctor who refuses to consider treatment for a symptomatic man with T of 295 despite a clear syndrome isn't either. The nuance lives in the middle.

Where to Get the Panel

Options:

• Your primary care physician — covered by insurance with proper coding (symptoms-based). Can order the full panel; sometimes LH/FSH need to be specifically requested.
• Online TRT clinic onboarding — PeterMD, Hone, Marek, etc. bundle an initial panel. Quality varies; make sure LH/FSH and sensitive estradiol are included.
• Direct-to-consumer labs (Quest Direct, LetsGetChecked, Marek Health labs): $100-250 cash-pay for a comprehensive panel. Useful for a second opinion or if your PCP declines to order.

Bottom Line

A real TRT workup is 10-11 tests, not one. Two morning total testosterone readings, free T, SHBG, LH, FSH, sensitive estradiol, prolactin, TSH, CBC, CMP, and PSA. Anything less leaves diagnostic information on the table and makes it easier to end up on the wrong treatment for your actual physiology. Expect to pay $100-250 out of pocket if uninsured; most online clinics bundle the panel at cost as part of onboarding.

Take your results with you to any clinician conversation. A doctor who won't look at LH isn't a doctor you want prescribing a lifelong controlled substance.

Sources

1. Bhasin S et al. "Testosterone Therapy in Men With Hypogonadism: An Endocrine Society Clinical Practice Guideline." J Clin Endocrinol Metab, 2018.
2. Mulhall JP et al. "Evaluation and Management of Testosterone Deficiency: AUA Guideline." J Urol, 2018.
3. Rosner W et al. "Position Statement: Utility, Limitations, and Pitfalls in Measuring Testosterone." J Clin Endocrinol Metab, 2007.
4. Handelsman DJ. "Mass Spectrometry, Immunoassay and Valid Steroid Measurements in Reproductive Medicine." J Clin Endocrinol Metab, 2014.
5. Lunenfeld B et al. "Recommendations on the Diagnosis, Treatment, and Monitoring of Hypogonadism in Men." Aging Male, 2021.