What Blood Tests Do You Need
Before Starting TRT?

Blood work is the foundation of responsible TRT. It determines whether you actually have low testosterone, identifies what's causing it, establishes baseline values for safety monitoring, and reveals other health issues that could affect treatment. Without comprehensive blood work, prescribing testosterone is guesswork — and the quality of your lab panel directly determines the quality of your care.

The problem is that most providers — both primary care physicians and telehealth companies — order woefully incomplete panels. A typical PCP might check total testosterone and a basic metabolic panel: 4 to 7 markers total. Most telehealth companies aren't much better. At Revive Low T Clinic, our initial panel includes 51 analytes, and each one is there for a specific clinical reason. Here's a breakdown of what we test and why.

The Hormone Panel

Total Testosterone

The headline number. Total testosterone measures all the testosterone in your blood — both the bound portion (attached to proteins) and the unbound (free) portion. Most labs define the "normal" reference range as 264 to 916 ng/dL, though many men become symptomatic when levels fall below 400 to 450 ng/dL. It must be drawn fasting, in the morning (before 10 AM), and confirmed on a second draw if initially low. This test alone is insufficient for diagnosis because it doesn't tell you how much testosterone is actually bioavailable.

Free Testosterone

This is arguably more important than total testosterone. Only about 2 to 3 percent of your testosterone circulates freely (unbound) — and this is the fraction that can bind to androgen receptors and produce biological effects. A man can have a total testosterone of 500 ng/dL but a low free testosterone if his SHBG is elevated — which would explain why he still has symptoms despite "normal" total T. Many providers skip this test, which means they're missing the most clinically relevant part of the picture.

Sex Hormone-Binding Globulin (SHBG)

SHBG is a protein produced by the liver that binds testosterone and makes it unavailable for tissue use. High SHBG effectively lowers your bioavailable testosterone even when total T looks adequate. SHBG increases with age, hyperthyroidism, liver disease, and certain medications. It decreases with obesity, hypothyroidism, and insulin resistance. Knowing your SHBG level helps your physician interpret your total testosterone value and predict how you'll respond to treatment.

Estradiol (E2)

Estradiol is the primary estrogen in men, produced when testosterone is converted by the aromatase enzyme. Baseline estradiol is important because elevated levels can cause symptoms that mimic or accompany low T — including water retention, mood changes, gynecomastia (breast tissue growth), and sexual dysfunction. On TRT, estradiol monitoring is essential because increasing testosterone levels also increases the substrate available for aromatization. If estradiol rises too high, side effects can occur even with optimal testosterone levels. Your physician uses this number to determine whether estradiol management is needed as part of your protocol.

Luteinizing Hormone (LH)

LH is produced by the pituitary gland and signals the testes to produce testosterone. This marker is critical for determining the cause of low testosterone. High LH with low testosterone (primary hypogonadism) suggests the testes are failing to respond to the brain's signal — often due to testicular damage, genetic conditions, or aging. Low LH with low testosterone (secondary hypogonadism) suggests the pituitary isn't sending the signal properly — which can be caused by pituitary tumors, medications, obesity, or other factors. The distinction affects treatment decisions and may prompt additional workup.

Follicle-Stimulating Hormone (FSH)

FSH, like LH, comes from the pituitary gland. It's primarily responsible for stimulating sperm production. Elevated FSH with low testosterone can indicate primary testicular failure. FSH is also important for fertility discussions — it helps assess baseline reproductive function before starting TRT, which suppresses both LH and FSH.

Prolactin

Prolactin is a pituitary hormone that, when elevated in men, can suppress testosterone production and cause sexual dysfunction, breast tissue changes, and other symptoms. Elevated prolactin can indicate a pituitary adenoma (a benign tumor) — a rare but important finding that would change the treatment approach entirely. This is one of the markers that most basic panels skip, and it's one of the most important to catch.

DHEA-S

DHEA-S is an adrenal hormone that serves as a precursor to both testosterone and estrogen. Low DHEA-S, which is common in men over 40, can contribute to fatigue, low libido, and poor immune function independently of testosterone levels. It also provides information about adrenal function. Some patients benefit from DHEA supplementation alongside TRT.

Cortisol

Cortisol is your primary stress hormone. Chronically elevated cortisol suppresses testosterone production (it directly competes with testosterone at the receptor level) and promotes visceral fat storage, muscle breakdown, and inflammation. Knowing your cortisol level helps determine whether chronic stress is contributing to your low testosterone and informs recommendations about stress management as part of your treatment plan.

The Metabolic Panel

Comprehensive Metabolic Panel (CMP)

The CMP covers 14 markers including glucose, calcium, sodium, potassium, carbon dioxide, chloride, BUN, creatinine, albumin, total protein, ALP, ALT, AST, and bilirubin. This panel provides a snapshot of your kidney function, liver function, blood sugar, and electrolyte balance. Liver function (ALT, AST) is particularly important as a baseline before starting TRT, since the liver plays a role in testosterone metabolism and SHBG production. Kidney function markers ensure your body can properly process and excrete metabolic byproducts.

Fasting Glucose and HbA1c

These two tests together give a complete picture of blood sugar regulation. Fasting glucose shows your blood sugar at the moment of the draw, while HbA1c reflects your average blood sugar over the past 2 to 3 months. This matters for TRT because low testosterone and insulin resistance form a bidirectional relationship — each makes the other worse. Many men with low T also have prediabetes or undiagnosed diabetes, and TRT can improve insulin sensitivity. Tracking these markers shows whether TRT is having the expected metabolic benefit.

Lipid Panel

Total cholesterol, LDL, HDL, and triglycerides. These are standard cardiovascular risk markers that provide a baseline and allow us to track any changes during TRT. Testosterone generally has favorable effects on lipids — reducing total cholesterol and triglycerides — but individual responses vary, and monitoring ensures your cardiovascular risk profile is trending in the right direction.

The Safety Panel

Complete Blood Count (CBC)

The CBC includes hemoglobin, hematocrit, red blood cell count, white blood cell count, and platelets. The most critical marker here for TRT is hematocrit — the percentage of your blood volume occupied by red blood cells. Testosterone stimulates red blood cell production, and if hematocrit rises too high (above 52 to 54%), blood becomes more viscous and the risk of blood clots increases. Your baseline hematocrit establishes the starting point from which we monitor for changes. Men who start with an already-elevated hematocrit may need closer monitoring or modified dosing.

PSA (Prostate-Specific Antigen)

PSA is a protein produced by the prostate gland. While TRT does not cause prostate cancer, PSA monitoring is standard practice for all men over 40 — and it's essential as a baseline before starting TRT. We track PSA trends over time: a stable PSA that stays within normal limits is reassuring, while a rapid rise (greater than 1.4 ng/mL in 12 months) or an absolute value above 4.0 ng/mL warrants urological referral for further evaluation.

Iron Studies (Ferritin, TIBC, Serum Iron)

Iron studies reveal whether you have iron deficiency (which can cause fatigue that mimics low T) or iron overload (hemochromatosis, which can actually cause low testosterone by damaging the pituitary gland and testes). Hemochromatosis is one of the most common genetic conditions in men of Northern European descent, and it's an often-overlooked cause of hypogonadism. If iron overload is present, it needs to be treated — and treating it may improve testosterone levels independently.

The Thyroid Panel

TSH, Free T4, Free T3

Thyroid dysfunction is one of the most common mimics of low testosterone symptoms. An underactive thyroid (hypothyroidism) causes fatigue, weight gain, brain fog, depression, low libido, and poor exercise tolerance — the same symptoms that bring men to a TRT clinic. If thyroid dysfunction is the underlying cause, treating it may resolve symptoms without the need for TRT. If both low testosterone and thyroid dysfunction are present, both need to be addressed. Skipping the thyroid panel means potentially missing a treatable condition.

Additional Markers

Vitamin D (25-hydroxyvitamin D)

Vitamin D deficiency is extremely common in the Pacific Northwest (Seattle sees limited sunlight for much of the year) and is associated with lower testosterone levels, poor immune function, depression, and decreased bone density. Multiple studies have shown a positive correlation between vitamin D levels and testosterone — men with adequate vitamin D tend to have higher testosterone levels. Supplementing vitamin D when deficient can modestly improve testosterone and provides independent health benefits.

Vitamin B12 and Folate

B12 deficiency causes fatigue, brain fog, and mood changes — symptoms that overlap with low T. It's particularly common in men taking metformin (a diabetes medication) or proton pump inhibitors, and in men with dietary restrictions. Identifying and correcting B12 deficiency ensures that these symptoms are properly attributed and treated.

C-Reactive Protein (CRP)

CRP is a marker of systemic inflammation. Chronic inflammation is associated with lower testosterone levels, increased cardiovascular risk, insulin resistance, and accelerated aging. A high CRP prompts investigation into inflammatory sources and provides context for the overall clinical picture. TRT has been shown to reduce CRP in some studies, and tracking this marker over time helps assess your overall inflammatory burden.

Why This Level of Testing Matters

The difference between a 4-marker panel and a 51-marker panel isn't just thoroughness for its own sake — it's the difference between treating a number and treating a patient. A comprehensive panel reveals whether your low testosterone is primary or secondary, whether reversible causes exist, whether other conditions need attention, and what monitoring baselines to establish. It allows your physician to design a treatment protocol that's truly individualized rather than one-size-fits-all.

At Revive, the 51-analyte panel is included in your first visit ($99). We draw labs in-house at our Seattle, Kirkland, and Federal Way locations — no separate lab appointment, no additional cost. Results are typically available within 3 to 5 business days, at which point your physician reviews them in detail and discusses your treatment options. This is the standard of care we believe every man considering TRT deserves. Learn more about our lab testing process or book your first visit.