Which Biomarkers to Test Before Starting a Peptide Protocol

The specific blood tests and biomarkers to establish at baseline before any peptide protocol—organized by compound class, with the reasoning behind each one.

Why Baseline Labs Matter More Than Most People Think

Baseline labs are not optional. They’re not nice-to-have. They are the foundation of responsible peptide use. Here’s why.

A baseline establishes your individual normal—not the population normal printed on a lab form. Reference ranges tell you what 95% of the general population looks like. Your baseline tells you what you look like before you change anything. That difference matters enormously. Your fasting glucose might be 95 mg/dL (well within the reference range), but when you start a GH secretagogue and it rises to 108, that 13-point shift is meaningful because you know where you started. Without a baseline, you have no idea whether that 108 is concerning or just you being you.

There’s also a critical distinction between monitoring for safety and monitoring for efficacy. Safety monitoring asks: “Is this causing harm?” Efficacy monitoring asks: “Is this working?” You need both. A baseline measurement allows you to answer both questions. Without it, you’re flying blind—you can’t attribute changes to the protocol, and you can’t catch emerging problems early.

This is also how you separate responsible providers from irresponsible ones. Responsible providers require baselines and retest on a schedule that matches the mechanism of the compound. Irresponsible ones skip this entirely or treat it as an afterthought. The first time someone tells you, “We don’t really need labs,” that’s your signal to find a different provider.

What happens when you skip baseline testing? You lose the ability to attribute changes to the protocol. You cannot distinguish between a drug effect and a coincidence. You cannot detect emerging problems until they’re obvious—and by then, they may be serious. You also cannot document safety for yourself or for your provider, which makes course correction harder and malpractice harder to defend.

The Universal Panel: What Everyone Should Test

Regardless of which peptide you’re using, some biomarkers matter for everyone. These are your foundation tests—the ones you order no matter what compound class you’re starting.

Complete Metabolic Panel (CMP)

The CMP is 14 measurements that tell you about your liver, kidneys, electrolytes, and baseline glucose. Specifically: glucose, BUN (blood urea nitrogen), creatinine, sodium, potassium, chloride, CO₂, calcium, albumin, total protein, bilirubin, AST, ALT, and alkaline phosphatase. Many peptides affect kidney and liver function. Some suppress appetite and can alter electrolytes through dietary change. A baseline CMP is non-negotiable.

Complete Blood Count (CBC)

The CBC measures your red blood cells, white blood cells, and platelets. Baseline hematological status matters because some peptides can affect immune function or red blood cell production. You need to know where you start.

Lipid Panel

Total cholesterol, LDL, HDL, and triglycerides. Some peptides—particularly GLP-1 agonists—have significant lipid effects. You need a baseline to measure improvement or catch deterioration.

Fasting Glucose and Fasting Insulin

These are separate from the CMP glucose (though the CMP glucose is usually fasting as well). You want a dedicated fasting glucose measurement and a fasting insulin measurement. From these two, you can calculate HOMA-IR (homeostatic model assessment for insulin resistance), which is a proxy for how insulin-resistant you are. HOMA-IR = (fasting glucose × fasting insulin) / 405. A baseline HOMA-IR tells you where your insulin sensitivity sits before you start anything. Many peptides affect glucose and insulin signaling, so this is essential.

Hemoglobin A1c (HbA1c)

HbA1c is your 3-month average glucose. It moves slower than fasting glucose, so baseline HbA1c gives you a picture of long-term glucose control before you start. This is especially important for GLP-1 protocols, where glucose improvement is the point, but also relevant for any protocol that touches glucose metabolism.

Thyroid Panel (TSH, Free T3, Free T4)

TSH (thyroid-stimulating hormone), free T3, and free T4. Some peptides have effects on thyroid function. You need to know if you start in a euthyroid (normal) state. Some GLP-1 agonists carry warnings about thyroid C-cell effects from rodent studies. A baseline TSH and free T3/T4 establish your starting point.

High-Sensitivity C-Reactive Protein (hsCRP)

hsCRP is a systemic inflammation marker. Many peptide protocols aim to reduce inflammation. A baseline hsCRP lets you measure that reduction. Baseline hsCRP <3 mg/L is generally considered low risk for cardiovascular disease. Higher values suggest chronic inflammation.

All of these tests are standard and inexpensive. They’re available through any direct-to-consumer lab testing service (Ulta Lab Tests, Quest, LabCorp, etc.). A provider who does not order at least this panel before you start any peptide protocol is not taking safety seriously.

GH Secretagogue-Specific Panel

If you’re using any GH secretagogue—CJC-1295 (no DAC), CJC-1295 (with DAC), ipamorelin, sermorelin, tesamorelin, hexarelin, GHRP-2, GHRP-6, or MK-677 (note: not a peptide)—you need additional testing beyond the universal panel.

IGF-1 (Insulin-Like Growth Factor 1)

IGF-1 is the critical marker for GH secretagogues. Here’s the physiology: When you administer a GH secretagogue, your pituitary secretes more growth hormone (GH). GH circulates to the liver, where it stimulates production of IGF-1. IGF-1 is the mediator of most of GH’s anabolic effects—the muscle building, the bone strengthening, the metabolic effects you want. But IGF-1 is also a growth factor, and like all growth factors, too much of it can be a problem.

Here’s what matters: A normal adult IGF-1 range is roughly 116–231 ng/mL (age-dependent; younger people trend higher, older people trend lower). “Normal” doesn’t mean “optimal for you.” And “normal” definitely doesn’t mean “safe on a GH secretagogue.” When you’re on a GH secretagogue, IGF-1 typically rises 20–40% above baseline. Some of that is expected and desired. But supraphysiological IGF-1—IGF-1 above, say, 250–280 ng/mL sustained—carries risks. Supraphysiological IGF-1 has associations with accelerated tumor growth, carpal tunnel syndrome, joint pain, and insulin resistance.

That’s why the baseline matters. If your baseline IGF-1 is 150 ng/mL and it rises to 210 on protocol, that’s a 40% increase but still within a reasonable range. If your baseline is 200 and it jumps to 280, that’s a warning sign. You need that baseline to interpret the on-protocol numbers.

Baseline IGF-1 should be obtained fasting (to standardize it as much as possible, though IGF-1 doesn’t vary as much with feeding as GH does). Some providers check it in the morning; morning is conventional but not strictly necessary.

IGFBP-3 (IGF-Binding Protein 3)

IGFBP-3 is a binding protein that carries most circulating IGF-1. It adds context to IGF-1 interpretation. IGFBP-3 is more stable than IGF-1 and has a longer half-life. On a GH secretagogue, IGFBP-3 rises alongside IGF-1. A high IGFBP-3 without a proportional rise in IGF-1 can indicate that IGF-1 is being bound up (sequestered)—which isn’t necessarily bad, but it’s useful information for interpreting your IGF-1 level. Most providers check both together.

Fasting Glucose and Insulin (Repeated from Universal Panel)

GH is diabetogenic—it antagonizes insulin secretion and raises fasting glucose. This is a known effect of GH secretagogue protocols. Your baseline fasting glucose and insulin establish where you start. On protocol, expect your fasting glucose to rise slightly; this is expected. The question is: how much? And does it stay in a defensible range? A rise from 95 to 105 is concerning but manageable. A rise from 95 to 125 is a signal to reassess the protocol dose or frequency.

HbA1c (Repeated from Universal Panel)

Long-term glucose control. If you’re on a GH secretagogue for months, HbA1c will trend upward. Baseline HbA1c lets you quantify that shift. Most providers recheck HbA1c every 3 months on a GH secretagogue protocol to ensure glucose control stays acceptable.

This is the critical point: If your provider does not check baseline IGF-1 and recheck it at 6–8 weeks and every 3 months thereafter while you’re on a GH secretagogue protocol, that’s a red flag. This is not optional. This is not something you can skip because you “feel fine.” IGF-1 doesn’t have a warning symptom—it just climbs. Without monitoring, you won’t know until something goes wrong.

The compounds in this class: CJC-1295 (no DAC)—a GHRH analog with a 15–30 minute half-life; CJC-1295 (with DAC)—the same GHRH analog with a drug affinity complex that extends the half-life to ~7 days; ipamorelin—a selective GHRP5 receptor agonist; sermorelin—pure GHRH; tesamorelin—a GHRH analog; hexarelin—a GHRP agonist; GHRP-2 and GHRP-6—synthetic GH-releasing peptides; and MK-677 (which is not a peptide, but a small-molecule GHRELIN receptor agonist). All of these work by stimulating GH secretion and therefore require the same IGF-1 monitoring.

GLP-1 / Metabolic Peptide Panel

GLP-1 agonists—semaglutide, tirzepatide, liraglutide, and the forthcoming retatrutide (a triple agonist)—work on the GLP-1 receptor to slow gastric emptying, increase satiety, improve insulin secretion, and reduce appetite. The baseline labs for this class focus on metabolic function, liver and kidney tolerance, and pancreatitis screening.

HbA1c and Fasting Glucose

These are the primary efficacy markers for a GLP-1 protocol. HbA1c tells you long-term glucose control; fasting glucose tells you fasting baseline. GLP-1 agonists improve both. Baseline HbA1c is particularly important because the whole point of the protocol is to lower it. Without a baseline, you can’t quantify improvement.

Fasting Insulin

Insulin resistance assessment. GLP-1s improve insulin sensitivity indirectly by reducing body weight and visceral fat. A baseline fasting insulin establishes your starting insulin resistance level. Many providers calculate HOMA-IR from fasting glucose and insulin at baseline and recheck it after 3 months to show improvement.

Lipid Panel

GLP-1 agonists improve lipid profiles—they lower triglycerides and improve the LDL/HDL ratio. You need a baseline lipid panel to measure that improvement. Many people starting GLP-1s have dyslipidemia (abnormal cholesterol), so capturing the before-and-after is important both for documentation and for motivation.

Liver Enzymes (ALT, AST)

GLP-1 agonists are metabolized hepatically. Baseline ALT and AST establish that your liver is functioning normally before you start. They’re part of the CMP, but they’re worth calling out specifically because liver function matters for drug metabolism. If your baseline ALT or AST is abnormally high, that’s a conversation with your provider before starting.

Kidney Function (Creatinine, eGFR, BUN)

Especially important for tirzepatide. Tirzepatide is a dual GLP-1/GIP receptor agonist with a ~5-day half-life and preferential renal clearance. If you have borderline or impaired kidney function, tirzepatide dosing may need adjustment. eGFR (estimated glomerular filtration rate) tells you your kidney function; creatinine and BUN are related markers. A baseline eGFR establishes your starting renal capacity.

Amylase and Lipase

These are pancreatic enzymes. GLP-1 agonists carry a warning about pancreatitis risk (though actual incidence is rare). Baseline amylase and lipase establish that your pancreas is functioning normally. If either is elevated at baseline, that’s a signal to assess pancreatitis risk more carefully before starting.

Thyroid Panel (TSH, Free T3, Free T4)

GLP-1 agonists carry a theoretical warning from rodent studies showing thyroid C-cell hyperplasia. In humans, the signal is much less clear, but baseline TSH and free T4 establish that your thyroid is normal before you start. Many providers recheck TSH every 6–12 months on a GLP-1 protocol as a precautionary measure.

Body Composition Baseline

Weight and waist circumference are not lab tests, but they’re measurements that belong in your baseline assessment for a GLP-1 protocol. The whole point of GLP-1s is weight loss and visceral fat reduction. You need a baseline weight and waist circumference to quantify that change. Some providers use more sophisticated body composition analysis (DEXA, bioelectrical impedance), but weight and waist circumference are the minimum.

The compounds: semaglutide (Ozempic, Wegovy)—a GLP-1 agonist with a ~7-day half-life; tirzepatide (Mounjaro, Zepbound)—a dual GLP-1/GIP agonist with a ~5-day half-life; liraglutide (Saxenda, Victoza)—a GLP-1 agonist with a ~13-hour half-life; and retatrutide (forthcoming)—a triple agonist hitting GLP-1, GIP, and glucagon receptors.

Sexual Health / Hormonal Peptide Panel

PT-141 (bremelanotide), gonadorelin, and kisspeptin are peptides that work on sexual function and reproductive hormones. These protocols require specialized hormonal baselines.

Male Panel

Total testosterone, free testosterone, SHBG (sex hormone-binding globulin), estradiol, LH (luteinizing hormone), FSH (follicle-stimulating hormone), prolactin, and PSA (prostate-specific antigen) if 40 or older.

Total testosterone ranges 300–1000 ng/dL in adult men (reference ranges vary by lab; most use 300–1000 or 250–1100). Free testosterone is the testosterone not bound to SHBG—it’s the biologically active form. Normal free testosterone is roughly 9–30 pg/mL. SHBG is the carrier protein for testosterone and estradiol; high SHBG binds more testosterone, lowering the free fraction. Estradiol in men should be roughly 15–40 pg/mL; too high increases water retention and gynecomastia risk, too low can impair sexual function. LH and FSH drive testosterone production in the testes; baseline LH and FSH establish your hypothalamic-pituitary-gonadal axis status. Prolactin suppresses GnRH (gonadotropin-releasing hormone) and can affect sexual function if elevated. PSA is a prostate cancer screening marker; if you’re over 40 and considering a sexual health peptide, baseline PSA is important.

Female Panel

Estradiol, progesterone, total testosterone, SHBG, LH, and FSH. The female hormone panel is different because baseline estradiol and progesterone tell you where you are in your menstrual cycle or menopausal status. Estradiol in reproductive-age women varies widely depending on cycle phase; roughly 30–400 pg/mL (wide range). Progesterone is <1 ng/mL in the follicular phase and 5–20 ng/mL in the luteal phase. Total testosterone in women is roughly 15–70 ng/dL. SHBG, LH, and FSH define the HPG axis status. For sexual health peptides like PT-141, knowing your baseline hormone profile is essential because these peptides work on a hormonal system.

Blood Pressure

PT-141 (bremelanotide) is a melanocortin agonist that causes transient hypertension. You need a baseline blood pressure to establish your resting BP before you start. During a PT-141 dose, BP can rise 10–20 mmHg acutely; knowing your baseline lets you identify whether that rise is significant for you.

Cardiovascular History Assessment

This is less a lab test and more a clinical conversation: Do you have a history of hypertension, coronary artery disease, arrhythmias, or stroke? Sexual health peptides like PT-141 affect blood pressure and heart rate. If you have cardiovascular risk, your provider needs to know before you start.

The compounds: PT-141 (bremelanotide)—a melanocortin receptor agonist for sexual arousal; gonadorelin—a GnRH analog that stimulates LH and FSH production; and kisspeptin—a hypothalamic neuropeptide that triggers GnRH secretion.

Tissue Repair / Recovery Peptide Panel

BPC-157 (body protection compound-157) and TB-500 (thymosin beta-4) are marketed as tissue repair peptides. The baseline testing here is more limited because clinical monitoring standards for these compounds do not exist.

Complete Metabolic Panel

Particularly liver function (ALT, AST, bilirubin). Both BPC-157 and TB-500 are metabolized by the body; baseline liver enzymes establish that your hepatic system is normal before you start. BPC-157 in particular has shown liver-protective effects in animal models, but human data is sparse. A baseline CMP is standard precaution.

Inflammatory Markers: hsCRP and ESR

hsCRP (high-sensitivity C-reactive protein) and ESR (erythrocyte sedimentation rate) are systemic inflammation markers. If you’re using BPC-157 or TB-500 for recovery or anti-inflammatory effects, baseline hsCRP and ESR give you something to measure against. That said, these compounds lack controlled clinical trial data, so there’s no established “expected” change.

The Honest Caveat

Here’s what you need to know: BPC-157 has been studied in 3 human trials (small, mostly observational). TB-500 has zero published human clinical trials. There is no established clinical monitoring standard for either compound because there is no robust human trial data defining what to monitor. Most practitioners design monitoring protocols based on pharmacological reasoning—what we know about the mechanism and what animal studies suggest—rather than on clinical protocol data that simply doesn’t exist.

This doesn’t mean these compounds are dangerous. It means we don’t have systematic human data. It means monitoring standards are educated guesses, not evidence-based. When a provider tells you, “We’ll monitor X, Y, and Z on BPC-157,” they’re usually extrapolating from animal data or clinical judgment, not from a randomized controlled trial. That’s not a condemnation—it’s an acknowledgment of what we don’t know. But it’s important to understand the distinction.

The compounds: BPC-157—a 15-amino-acid peptide derived from gastric juice with pro-angiogenic and tissue-protective effects in animal models; and TB-500 (thymosin beta-4)—a 43-amino-acid peptide involved in wound healing and tissue repair in animal models.

Immune / Anti-Inflammatory Peptide Panel

Thymosin Alpha-1, LL-37, and KPV are peptides marketed for immune support and inflammation modulation. The evidence levels differ significantly, which matters for monitoring standards.

Complete Blood Count with Differential

Baseline immune cell counts: WBC (white blood cells), neutrophils, lymphocytes, monocytes, eosinophils, basophils. If you’re using an immune-modulating peptide, you need to know your starting immune cell counts. Thymosin Alpha-1 has published clinical trial data showing immune effects; LL-37 and KPV do not. A baseline CBC with differential lets you track any changes.

hsCRP and ESR

Systemic inflammation markers. If your protocol is aimed at reducing inflammation or improving immune function, baseline hsCRP and ESR establish your starting point.

Immunoglobulin Levels (IgG, IgA, IgM)

If available through your lab. These are antibody measurements that reflect immune function. They’re not routine, but some providers check them as part of an immune assessment on Thymosin Alpha-1 protocols.

Important Context: Thymosin Alpha-1 vs. LL-37 vs. KPV

Thymosin Alpha-1 is approved as a drug in 35+ countries (China, Russia, many others) with established clinical trial data showing immune effects. It has a real monitoring standard. LL-37 is a naturally occurring antimicrobial peptide with preclinical data only—no clinical trials in humans. KPV is a 3-amino-acid peptide (part of the Thymosin Alpha-1 sequence) with minimal human data. When you see these three grouped together, remember: Thymosin Alpha-1 has clinical evidence; the others are extrapolated from preclinical work.

The compounds: Thymosin Alpha-1—a 28-amino-acid peptide secreted by the thymus that enhances T-cell function (Approved Drug status in 35+ countries); LL-37—a cathelicidin antimicrobial peptide involved in innate immunity (preclinical only); and KPV—a tripeptide fragment of Thymosin Alpha-1 (minimal human evidence).

How Often to Retest

Baseline is the start. But you need a retesting schedule. Here’s the general framework.

Initial Baseline: Before Protocol Starts

All the tests covered above should be done before you take the first dose. Not “a few days in,” not “we’ll check after one week”—before. This establishes your true baseline.

First Follow-up: 6–8 Weeks

For most peptides, 6–8 weeks is the standard first recheck. This is long enough for most biomarkers to shift meaningfully, but short enough to catch problems early. Which tests? Depends on the compound:

• GH secretagogues: IGF-1, IGFBP-3, fasting glucose, fasting insulin. This is non-negotiable.
• GLP-1s: HbA1c (though HbA1c moves slowly; you may not see full change at 6–8 weeks), fasting glucose, weight, lipids.
• Sexual health peptides: Total/free testosterone, estradiol, LH, FSH if on protocol for hormonal effects.
• Tissue repair peptides: CMP, hsCRP. No established standard, so this is provider-dependent.
• Immune peptides: CBC with differential, hsCRP.

Ongoing: Every 3–6 Months

For long-term protocols (anything lasting more than 2–3 months), establish a regular retesting schedule:

• GH secretagogues: IGF-1 every 3 months is standard. Some providers do it every 6 months if stable, but 3-month intervals are safer. HbA1c every 3 months to monitor glucose. CMP every 6 months.
• GLP-1s: HbA1c every 3 months (especially if titrating doses). Lipids every 3–6 months. Kidney function every 6 months (especially tirzepatide). Weight/waist circumference every month informally, formally every 3 months.
• Sexual health peptides: Testosterone panel every 3–6 months depending on protocol goals. Blood pressure at each visit or biweekly if concerning.
• Tissue repair peptides: CMP every 3 months, hsCRP every 3–6 months. Again, no established standard.
• Immune peptides: CBC every 3–6 months, hsCRP every 3–6 months.

Urgent Retesting: New Symptoms or Unexpected Side Effects

If you develop new symptoms—joint pain on a GH secretagogue, severe nausea on a GLP-1, palpitations on a sexual health peptide—retest immediately. Don’t wait for your scheduled recheck. New symptoms are a signal that something has changed and you need data.

This is the template. Your provider may modify it based on your specific protocol, health history, or biomarker results. The key principle: don’t guess. Test.

Reading Your Results: What Matters vs. What Doesn’t

Your lab results come back with numbers and a reference range. Here’s how to think about them.

Reference Ranges Are Population Averages, Not Optimization Targets

The reference range printed on your lab report is the range that includes 95% of the population tested by that lab. It’s a statistical bell curve. It is not “optimal.” It is not “ideal for you.” It is “common.” A fasting glucose of 95 mg/dL is within the reference range (typically 70–100) and therefore “normal,” but if your baseline is 85 and you’re on a GH secretagogue and it rises to 95, that’s a 12% increase—meaningful, even if still “normal.”

Don’t confuse “in range” with “good.” The reference range is a starting point for interpretation, not the endpoint.

Your Own Trend Matters More Than Any Single Number

If your baseline IGF-1 is 160 ng/mL and your 8-week recheck is 210, that’s a 31% increase. That’s meaningful. The absolute value of 210 might be “within range,” but the trajectory is what signals whether your protocol is working as intended. Conversely, if your baseline is 240 and your recheck is 250, that’s only a 4% increase—even though the absolute value of 250 might look high, the stability is reassuring.

Your provider should be tracking your individual trajectory, not just comparing your number to a reference range.

When “Normal” Isn’t Reassuring

Example: Your baseline IGF-1 is 220 ng/mL. That’s in the reference range. But it’s on the high end. When you start a GH secretagogue and it rises to 280, you’ve just crossed into what many consider supraphysiological. The fact that your baseline was “normal” doesn’t make a 280 safe. Context matters.

When “Abnormal” Isn’t Alarming

Example: You’re on a GH secretagogue and your fasting glucose rises from 92 to 108 mg/dL. That’s “high” if we’re being literal, but it’s not alarming if your baseline was 92 and your protocol is intentional. GH is diabetogenic. A modest rise in fasting glucose is expected. The question is: is the rise manageable? Is your HbA1c staying acceptable? Is your provider monitoring it? If yes to all three, then 108 is not an emergency—it’s a managed drug effect.

Clinical Context Matters More Than Raw Numbers

The number alone doesn’t tell the story. Here’s what does: Your baseline. Your current result. The expected effect of your protocol. Your symptoms. Your other biomarkers. Your personal risk factors. A good provider will contextualize your results, not just list them.

You Need a Provider Who Interprets, Not Just Orders

There’s a difference between a provider who orders labs and a provider who reads them thoughtfully. A provider who orders labs can be a robot. A provider who reads them needs to understand pharmacology, your goals, your risk tolerance, and the meaning of change. If your provider sends you lab results with no interpretation or context, ask questions. Make them explain what the changes mean and whether your protocol is working as intended or needs adjustment.

The bottom line: You are not a reference range. You are an individual with a baseline, a protocol, and goals. Your results matter in context.

Frequently Asked Questions

Can I just use my regular doctor’s blood work instead of ordering new labs?

Possibly some of it. If your regular doctor ran a CMP, CBC, lipid panel, and thyroid panel in the last 3 months, you can use those as your baseline for the universal panel. But peptide-specific tests—IGF-1 for GH secretagogues, for example—your regular doctor probably didn’t order. And your doctor’s baseline isn’t necessarily timed to your protocol start, which matters. Ideally, run a fresh baseline within a week of starting your peptide. If you have recent labs (within 3 months), ask your provider whether they’re acceptable as baseline or if you should retest.

How much does baseline lab testing cost?

The universal panel (CMP, CBC, lipid panel, fasting glucose and insulin, HbA1c, TSH/free T3/T4, hsCRP) costs $150–$250 depending on your lab. GH secretagogue-specific tests add IGF-1 and IGFBP-3 ($50–$100). GLP-1-specific tests add amylase and lipase plus the baseline measurements already listed ($30–$80). Sexual health panels with full hormone testing (T, free T, SHBG, estradiol, LH, FSH, prolactin) run $150–$200. Total baseline cost for a comprehensive protocol: $300–$400. Direct-to-consumer labs like Ulta Lab Tests and Marek Diagnostics typically cost less than ordering through a traditional lab. Some providers absorb lab costs; others pass them to you.

What if my provider doesn’t require baseline labs?

Find a different provider. This is non-negotiable. A provider who does not establish a baseline before you start a peptide protocol is not taking your safety seriously. This is a red flag—not a minor preference, a genuine signal that your provider’s standards are below responsible care. You can order your own labs through a direct-to-consumer service and bring them to your provider, but ideally, use a provider who makes baseline testing a requirement.

Do I need to fast before peptide-related blood work?

For most tests, yes. Fasting glucose, fasting insulin, and lipid panel all require 8–12 hours of fasting (no food, water is fine). IGF-1 is more stable and doesn’t require fasting, though most labs recommend it for standardization. TSH and free T3/T4 don’t require fasting. CMP and CBC don’t require fasting. Ask your lab for their specific fasting requirements, but assume 8–12 hours fasting for glucose, insulin, and lipids.

Can I order these tests myself without a doctor?

Yes. Direct-to-consumer lab testing services (Ulta Lab Tests, Quest, LabCorp, Marek Diagnostics, and others) allow you to order tests without a provider’s order. You pay out-of-pocket, get your results, and can take them to a provider for interpretation. This is perfectly legal and increasingly common. The advantage: you control the timing and the tests. The disadvantage: you’re paying retail and you may not know which tests to order without guidance. Many people use DTC labs for baseline and recheck testing, then work with a telehealth provider for interpretation and protocol management.

How long should I wait after stopping a protocol before retesting?

It depends on the compound’s half-life. GH secretagogues like CJC-1295 (with DAC) have a 7-day half-life; give it 3–4 weeks (5 half-lives to clear). Semaglutide has a ~7-day half-life; 3–4 weeks. Short-acting peptides like ipamorelin or CJC-1295 (no DAC) clear in hours to days; you can retest at 1–2 weeks. For GLP-1 agonists like semaglutide, wait 3–4 weeks before retesting because it takes that long to fully clear and for metabolic biomarkers to stabilize. Talk to your provider about the specific timeline for your compound.

What’s the difference between IGF-1 and growth hormone testing?

Growth hormone (GH) is the hormone secreted by your pituitary. It’s short-lived (half-life ~20 minutes), variable throughout the day, and difficult to interpret. IGF-1 is the hormone produced by your liver in response to GH. It’s stable throughout the day and reflects your average GH exposure over the past 24–48 hours. On a GH secretagogue protocol, you want to monitor IGF-1, not GH. GH testing is rarely useful for peptide protocols because GH pulses and fluctuates too much. IGF-1 is the meaningful marker.

Should I test for peptide antibodies?

Not routinely. Antibodies to peptides can develop with long-term use of some compounds (particularly longer-acting peptides like CJC-1295 with DAC), but testing for them is not standard. If you notice a loss of efficacy over time on a long-acting GH secretagogue, your provider may test for neutralizing antibodies to determine whether antibody formation is blunting the effect. But this is reactive testing, not baseline screening. Don’t order an antibody panel unless you have a specific reason (loss of effect, not just routine monitoring).