The bloodwork guide.
The labs people on TRT, GLP-1, or peptide protocols tend to track: what each marker actually measures, why it's followed, what timing does to the numbers, and how to read the difference between a reference range and what's optimal for you. This explains markers. It does not interpret your specific results. That's your clinician's job.
Reviewed June 1, 2026
- Bloodwork turns a protocol from guesswork into something measurable and comparable over time.
- When you draw changes the number: trough vs peak for testosterone, fasting vs fed for metabolic markers. Consistency matters more than any single value.
- Reference ranges are population statistics, not personal targets. They tell you where 95% of a healthy reference population falls, not where you should be.
- The goal of tracking labs is the trend over time, not chasing a single out-of-range value.
Why timing transforms your results.
The same person can have testosterone levels that differ by 50–100% depending on when they draw: trough (just before the next injection) vs peak (24–48 hours after). Metabolic markers like insulin and triglycerides change significantly with fasting status. Testosterone itself varies by up to 30% from early morning (natural peak, approximately 6–10 AM) to late afternoon. These aren't errors. They're real physiological variation that needs to be controlled to make trend data meaningful.
Testosterone: total, free, and SHBG.
Total testosterone measures all circulating testosterone: bound to SHBG (sex hormone-binding globulin), bound to albumin, and unbound. The assay method matters: immunoassay (the older, more common method) has meaningful cross-reactivity with other steroids and can be inaccurate in ranges outside the normal male reference, particularly at low or high values. Liquid chromatography–tandem mass spectrometry (LC-MS/MS) is the gold-standard method, used by reference labs and most academic centres. It is more accurate across the range and should be requested if precision matters.
- 01Total testosterone. The standard clinical measure. Reference range approximately 300–1,000 ng/dL in adult men (varies by assay and lab; ±10–20% lab-to-lab variation is normal). Morning draw essential for consistency.
- 02Free testosterone. The unbound, biologically active fraction: roughly 1–3% of total. The gold standard method is equilibrium dialysis; direct free testosterone immunoassays are less reliable. Calculated free testosterone (from total T, SHBG, albumin) is widely used but has its own limitations. Most useful when total T is borderline and SHBG is suspected to be abnormal.
- 03SHBG (sex hormone-binding globulin). The binding protein that determines how much testosterone is free vs bound. SHBG is elevated by age, liver disease, and oestrogen; suppressed by obesity, insulin resistance, and androgens. High SHBG means less free testosterone despite normal total T; low SHBG means more free T with lower total T. Understanding SHBG explains why the same total T reads very differently across people.
Reference ranges are population-based, not individual optima. They represent the range containing 95% of a reference “healthy” population, which includes people with undiagnosed conditions, sedentary people, people across wide age ranges, and people who have never felt well or felt optimally well. “Within range” does not mean “optimal for you.” A trend from one value to another, tracked consistently over months, is more informative than where a single draw falls relative to a printed range.
Estradiol: why the assay type matters.
Estradiol (E2) in men is a functional hormone, essential for bone health, cardiovascular protection, mood, and erectile function, not just a problem marker. When it's tracked, the assay choice makes a large practical difference.
- 01Standard immunoassay (LC/IA). Lower detection limit approximately 15 pg/mL. Can't reliably detect low E2. If you're on an aromatase inhibitor that suppresses E2 below 15, you'll get a result that says “low” but not how low. Not specific to estradiol either: it can cross-react with other oestrogens.
- 02Sensitive / LC-MS/MS assay. Lower detection limit approximately 1–5 pg/mL. Detects true low E2. Recommended for men on TRT or AI, and postmenopausal women. Request the “sensitive estradiol” or “LC-MS/MS estradiol” specifically. It's not the default.
- 01Symptoms associated with high E2 in men: gynecomastia (breast tissue growth), water retention, mood changes, and in some men reduced libido or erectile dysfunction. Not universal. Many men feel fine with E2 values that would be flagged as high by a printed range.
- 02Symptoms associated with low E2 in men: joint pain, reduced bone mineral density over time, mood changes including depression, and in some men erectile dysfunction. These risks are often underappreciated in communities that focus on “crashing E2.”
Complete blood count (CBC): hematocrit and beyond.
The CBC reports the three main cell lineages in blood: red blood cells, white blood cells, and platelets. On TRT, the primary concern is erythrocytosis (elevated red blood cells), but the white cell differential and platelet count also provide clinical information.
- 01Hematocrit (Hct). Percentage of blood volume occupied by RBCs. The key TRT safety marker. Reference: 38–50% in men. Endocrine Society guideline threshold for TRT modification: >54%.
- 02Haemoglobin (Hgb). The oxygen-carrying protein inside RBCs. Rises with hematocrit. Reported in g/dL; rises with TRT similarly to Hct.
- 03WBC differential. Breaks down white blood cells by type (neutrophils, lymphocytes, monocytes, eosinophils, basophils). TRT has minimal effect on WBC count. Markedly elevated eosinophils (>1,500/µL) warrant investigation for allergic or parasitic disease; elevated basophils are associated with myeloproliferative conditions.
- 04Platelets. Clotting cells. Not directly affected by TRT but important context for cardiovascular risk assessment alongside an elevated hematocrit.
Lipid panel.
The standard lipid panel reports total cholesterol, LDL-C, HDL-C, triglycerides, and calculated VLDL. Fasting vs non-fasting affects triglycerides most significantly (typical rise of 20–30 mg/dL non-fasting), while LDL and HDL are less affected. The 2016 EAS/EFLM consensus and ACC/AHA guidelines now endorse non-fasting lipid panels for screening, but fasting remains standard for baseline and treatment-monitoring purposes.
- 01HDL cholesterol. Modest reduction of approximately 2–6 mg/dL at therapeutic TRT doses. Mechanism: upregulation of hepatic lipase and SR-B1 receptor. Effect is dose-dependent and route-dependent: injectable testosterone (with higher peaks) tends to produce slightly larger HDL reductions than transdermal. Supraphysiological doses (bodybuilding range) can suppress HDL by 50% or more.
- 02LDL cholesterol. Effects are small and inconsistent across studies: some meta-analyses find modest reduction (~2 mg/dL), others find no significant change. Not typically the primary lipid concern on TRT.
- 03Triglycerides. The most consistently positive lipid finding: meta-analyses show TRT reduces triglycerides by approximately 28–31 mg/dL on average, linked to improved insulin sensitivity and reduced visceral fat. The magnitude of benefit is larger in men with baseline metabolic dysfunction.
- 04Oral testosterone undecanoate worst-case. Oral TU (Jatenzo/Tlando) shows the worst lipid profile: HDL reduction ~14% vs ~3% for transdermal, LDL increase ~6%, triglycerides increase ~13%. 17-alpha-alkylated oral androgens (methyltestosterone, now rare) are hepatotoxic and produce severe lipid changes. Injectable and transdermal formulations do not carry these risks.
Metabolic markers.
- 01Fasting glucose. Blood glucose after 8–12 hours of fasting. Reference: 70–99 mg/dL normal, 100–125 mg/dL pre-diabetes, ≥126 mg/dL diabetes by ADA criteria. Central for GLP-1 monitoring (primary therapeutic target) and for GH-secretagogue protocols (GH is counter-regulatory to insulin and can worsen insulin sensitivity).
- 02HbA1c (glycated haemoglobin). The average blood glucose over the prior 2–3 months, expressed as a percentage. Reference: below 5.7% normal, 5.7–6.4% pre-diabetes, ≥6.5% diabetes. Not affected by fasting; can be drawn any time. The standard tracking marker for GLP-1 therapy efficacy in diabetes.
- 03Fasting insulin and HOMA-IR. Fasting insulin reflects insulin resistance. HOMA-IR (homeostatic model assessment of insulin resistance) = (fasting glucose mg/dL × fasting insulin µIU/mL) ÷ 405. Higher values indicate more insulin resistance. Useful for tracking metabolic response to interventions like GLP-1 therapy, diet, or exercise. Reference ranges are not uniformly standardised across labs.
Liver and kidney function.
- 01AST and ALT (liver enzymes). Released when liver cells are damaged. Injectable and transdermal testosterone are not typically hepatotoxic at therapeutic doses. Liver enzyme elevations on TRT are uncommon. 17α-alkylated oral steroids (methyltestosterone, now rarely used) were hepatotoxic and are the historical reason liver enzymes are included in TRT monitoring. Persist in the panel as a precautionary baseline.
- 02GGT (gamma-glutamyl transferase). Elevated by liver stress, alcohol, and bile duct problems. A non-specific marker; often elevated in the metabolic syndrome regardless of TRT.
- 03BUN and creatinine / eGFR (kidney function). Testosterone at therapeutic doses has minimal direct kidney effect. eGFR (estimated glomerular filtration rate, calculated from creatinine) is essential for GLP-1 users. GI side effects causing dehydration can impair kidney function, and GLP-1 dosing may be adjusted in chronic kidney disease. Important baseline for anyone over 50 or with metabolic risk factors.
Thyroid panel.
Thyroid hormones regulate metabolic rate, body composition, mood, cholesterol, and cardiovascular function. Undiagnosed thyroid dysfunction mimics many of the symptoms that drive people to explore TRT or peptides. The panel has nuance: knowing which markers to use and what they actually tell you changes the clinical picture.
- 01TSH (thyroid-stimulating hormone). The most sensitive screening marker. TSH is inversely correlated with thyroid hormone levels: a small drop in free T4 causes a disproportionately large TSH rise (roughly log-linear). Reference range: 0.4–4.0 mIU/L on most lab reports, though some guidelines suggest the upper normal limit may be closer to 2.5 mIU/L based on studies excluding people with subclinical disease.
- 02Free T4. T4 is the primary thyroid secretory product but biologically a prohormone; peripheral deiodination converts it to the active T3. Free T4 (the unbound, bioavailable fraction) reflects thyroid gland output. Normal FT4 + high TSH = subclinical hypothyroidism (gland is failing, pituitary compensating).
- 03Free T3. The biologically active form, with approximately 15× higher receptor affinity than T4. About 80% is produced by peripheral conversion of T4 (via deiodinase enzymes), not directly from the thyroid. Low FT3 with normal FT4 indicates poor T4-to-T3 conversion, caused by selenium/zinc deficiency, chronic stress, liver dysfunction, or a DIO2 gene polymorphism present in 12–36% of people.
- 04Reverse T3 (rT3). An inactive metabolite of T4, produced when the body prioritises shutting down metabolism (severe illness, extreme caloric restriction, chronic stress). The Endocrine Society and ATA do not include rT3 in standard thyroid assessment. Useful primarily for differentiating euthyroid sick syndrome from true hypothyroidism in critical illness. Widely tested by functional medicine practitioners despite limited guideline support.
- 05Thyroid antibodies (TPO, TgAb). Markers of autoimmune thyroid disease (Hashimoto's). Elevated in 90–95% of Hashimoto's patients. Present in approximately 10–15% of the general population, many of whom are currently euthyroid but at elevated risk of future hypothyroidism. Test when TSH is abnormal or symptoms suggest autoimmune cause.
Inflammation markers: hs-CRP.
High-sensitivity C-reactive protein (hs-CRP) measures the same protein as standard CRP but at a much lower detection threshold, sensitive enough to stratify cardiovascular risk in people without active inflammation. Standard CRP is useful for detecting acute illness; hs-CRP is useful for assessing chronic low-grade inflammatory burden.
- 01<1.0 mg/L: Low cardiovascular risk.
- 021.0–3.0 mg/L: Intermediate cardiovascular risk.
- 03>3.0 mg/L: High cardiovascular risk.
- 04>10 mg/L: Likely acute inflammation or infection. Repeat after the acute process resolves before using for CV risk assessment.
- 05Units warning. hs-CRP is reported in mg/L; standard CRP in mg/dL. Misreading units creates a 10× error in either direction. Always check the unit on the lab report.
The JUPITER trial (Ridker et al., 2008 NEJM, n=17,802) demonstrated that statin therapy in people with LDL <130 mg/dL but hs-CRP ≥2.0 mg/L reduced major cardiovascular events by 44%. This established hs-CRP as an actionable marker beyond the lipid panel and was incorporated into the 2019 ACC/AHA guidelines as a “risk enhancer” for statin decision-making. The Reynolds Risk Score, which adds hs-CRP and family history to the Framingham model, reclassifies approximately 20% of intermediate-risk individuals into higher or lower risk groups with better calibration.
Reference ranges are not optimal ranges.
This is possibly the most important concept in interpreting labs. A reference range is a statistical range covering 95% of a reference population, usually described as “healthy adults” but in practice including a wide spectrum of age, fitness, diet, and undiagnosed conditions. Being “in range” means you're not in the 5% most extreme. It says nothing about whether your number is the best it can be for you, or whether a number at the high end of normal is meaningfully different from one at the low end. The same lab value means different things at different ages, body compositions, and in different clinical contexts.
Protocol-specific panels.
- 01Baseline (before starting): Total testosterone (two morning draws; Endocrine Society requires confirmation), free testosterone, SHBG, LH, FSH (to distinguish primary vs secondary hypogonadism), estradiol (sensitive assay), PSA (men over 40), CBC with hematocrit, lipid panel, CMP (comprehensive metabolic panel), TSH.
- 023 months: Total testosterone (trough draw), CBC with hematocrit, PSA. Enough to catch erythrocytosis early and confirm therapeutic range.
- 036 months: Total testosterone, free testosterone, estradiol (if symptomatic), CBC, PSA, lipid panel, CMP.
- 04Annually (if stable): Full repeat of the above.
- 01Baseline: HbA1c, fasting glucose, fasting insulin, lipid panel, CMP (kidney and liver function), CBC, TSH.
- 023–6 months: HbA1c, fasting glucose, lipid panel, kidney function (eGFR; GI side effects and dehydration risk). Lipase/amylase if abdominal symptoms.
- 03Annually: Full panel repeat. Thyroid (TSH, and calcitonin if nodular thyroid disease or symptoms) per label guidance.
- 01Baseline: IGF-1 (reflects cumulative GH exposure), fasting glucose, HbA1c, fasting insulin, TSH, free T4, free T3 (thyroid, see above), CMP, CBC.
- 024–8 weeks: IGF-1 (check protocol is producing response), fasting glucose.
- 033 months and every 3–6 months: IGF-1, fasting glucose, HbA1c, thyroid panel. MK-677 specifically produces the most sustained IGF-1 elevation and highest insulin resistance risk, so more frequent glucose monitoring is warranted.
FAQ.
What bloodwork should I get on TRT?
Baseline before starting: total testosterone (twice, morning draws), free testosterone, SHBG, LH/FSH, estradiol (sensitive assay), PSA (men 40+), CBC, lipid panel, CMP, TSH. Follow-up at 3 months: testosterone trough, CBC with hematocrit, PSA. At 6 months and annually: full panel. Your clinician will set the exact panel. This is a general framework.
Why is it called 'trough' testosterone?
For injectable testosterone, the trough is the lowest point in the dosing cycle, measured just before the next injection. Because testosterone levels drop significantly between injections (a 2-fold difference between peak and trough is common with weekly injection), consistently drawing at the same point in the cycle (trough is standard) makes values comparable over time.
Why does my lab show a different reference range than my friend's?
Reference ranges are set by each lab based on their assay and their reference population. Lab-to-lab variation of 10–20% for testosterone is normal. Comparing your testosterone result from Lab A to a result from Lab B is not meaningful. Always compare results from the same lab, same assay, drawn at the same time of day and same point in your injection cycle.
What does high estradiol actually feel like?
It varies considerably between people. Some men with elevated estradiol feel nothing; others experience gynecomastia (breast tissue growth), water retention, mood changes, or reduced libido. Some men report these symptoms with estradiol levels that others tolerate fine. Symptoms in context of a clinical picture matter more than a number alone.
Should I request free testosterone or total testosterone?
Both are clinically useful. Total testosterone is the standard first-line measure. Free testosterone adds information when total is borderline or when SHBG is suspected to be abnormal (e.g., in obesity, which suppresses SHBG, making free T higher than total T implies). Request both if available, and specify the equilibrium dialysis free T method for the most accurate measurement.
Do GLP-1 drugs affect liver enzymes?
GLP-1 drugs can improve liver enzyme levels in people with fatty liver disease (NAFLD/NASH): reduced hepatic fat from weight loss and improved insulin sensitivity typically brings AST and ALT down. They don't cause liver enzyme elevation in routine use. Baseline liver function is checked before starting to establish a reference point.
What is IGF-1 and when should I check it?
IGF-1 (insulin-like growth factor 1) is produced by the liver in response to growth hormone signalling. It reflects cumulative GH exposure much better than a single GH measurement (which is pulsatile). Relevant for anyone using GH secretagogues (CJC-1295, ipamorelin, sermorelin, GHRP-6, MK-677). Check at baseline and at 4–8 weeks after starting to see if the protocol is affecting GH output. Elevated IGF-1 carries theoretical cardiovascular and cancer-promotion concerns with sustained elevation above the upper reference range.
Is hs-CRP the same as CRP?
Same protein, different assay sensitivity. Standard CRP can't reliably detect values below ~1 mg/dL (10 mg/L), useful for detecting acute infection but useless for cardiovascular risk stratification. hs-CRP detects values down to 0.03–0.15 mg/L, which is the range where cardiovascular risk differs. Always check units: hs-CRP is in mg/L, standard CRP often in mg/dL. Misreading creates a 10× error.
Sources.
- [1]Bhasin S et al.: Testosterone Therapy in Men With Hypogonadism: Endocrine Society Clinical Practice Guideline (monitoring) · J Clin Endocrinol Metab, 2018
- [2]Pearson TA et al.: Markers of inflammation and cardiovascular disease: CDC/AHA workshop · Circulation, 2003
- [3]Ridker PM et al.: Rosuvastatin to prevent vascular events in men and women with elevated CRP (JUPITER) · N Engl J Med, 2008
- [4]Jorgensen JO et al.: Growth hormone and thyroid hormone: T4-to-T3 conversion dose-dependent · J Clin Endocrinol Metab, 1994
- [5]Davis SR et al.: Global Consensus Position Statement on the Use of Testosterone Therapy for Women · J Clin Endocrinol Metab, 2019
- [6]Testosterone erythrocytosis mechanisms: hepcidin and EPO · Endocrine Connections, 2024
- [7]Testosterone and lipids: meta-analysis of effects on HDL, LDL, triglycerides · PubMed / NCBI
- [8]ATA/ATA hypothyroidism guideline: thyroid panel interpretation · ATA / PubMed
- [9]Ridker PM: Reynolds Risk Score for cardiovascular risk prediction (men and women) · PMC2752381
- [10]Free testosterone measurement: equilibrium dialysis vs calculated vs immunoassay · PubMed / NCBI
- [11]LC-MS/MS testosterone assay accuracy vs immunoassay · PubMed / NCBI
- [12]Sensitive estradiol assay (LC-MS/MS) in men: clinical utility · PubMed / NCBI
Cite this page
PepCue. “The bloodwork guide.” PepCue, reviewed June 1, 2026. https://www.pepcue.app/guides/bloodwork.
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