Peptide Blood Work Guide: What Labs to Run Before and During Peptide Therapy

If you are running a peptide protocol — research-use or compounded — and you are not collecting blood work, you are guessing. Baseline labs give you a starting point. Repeat labs at 4 weeks, 8-12 weeks, and quarterly thereafter tell you whether the protocol is doing what you want and whether it is causing harm you cannot feel yet. This page maps the specific labs to the specific peptide class, with primary-source backing where it exists.

One quick clarification: 'peptide blood work' on Google can mean two different things. Some readers land here looking for B-type natriuretic peptide (BNP) — a cardiac marker doctors use in heart failure workups. If that is what you need, talk to your physician or see resources like Cleveland Clinic's BNP page. The rest of this guide is about lab monitoring when you are using therapeutic or research peptides like BPC-157, semaglutide, CJC-1295/Ipamorelin, or tirzepatide.

A baseline panel turns your future blood work into a comparison instead of a snapshot. Population reference ranges are wide because they have to fit millions of people. Your own values within those ranges are the real reference point.

Without a baseline, a fasting glucose of 98 mg/dL on month 3 means very little. With a baseline of 78 mg/dL, that same 98 is a 25-point rise that warrants attention — common with growth hormone secretagogues. Without a baseline, an IGF-1 of 240 ng/mL is fine. With a baseline of 140, that 240 may signal a meaningful response, or it may signal that you are pushing the dose too hard. The baseline is the difference.

This is the panel that covers the safety floor for any peptide protocol. Add protocol-specific markers from the next section based on what you are actually using.

Different peptide classes shift different markers. The baseline panel above plus the class-specific additions below covers most research-use protocols.

These compounds push the pituitary to release more growth hormone, which then drives IGF-1 production in the liver. IGF-1 is the gold-standard efficacy marker because it smooths out the short GH spikes that are hard to catch on a single draw.

Tesamorelin is the only FDA-approved GHRH analog and the only one with trial-grade IGF-1 response data: in HIV-associated lipodystrophy patients, mean IGF-1 rose roughly 81% from baseline. CJC-1295 paired with a GHRP has shown IGF-1 elevations of 50-150% in research contexts, but those are not FDA-approved settings — the monitoring logic is extrapolated from approved-drug data.

This is the class with the most rigorous trial data because semaglutide (Ozempic, Wegovy) and tirzepatide (Mounjaro, Zepbound) are FDA-approved. The SUSTAIN program for semaglutide and the SURPASS program for tirzepatide reported HbA1c reductions of 1.5-1.8% and up to 2.6% respectively across 40-52 week trials. The FDA labels themselves spell out the monitoring expectations.

Human trial data on BPC-157 and TB-500 is limited. Most of the safety record is from animal studies plus community use; neither is FDA-approved. Lab monitoring here is mostly safety screening plus indirect efficacy markers (inflammation).

IGF-1 is the marker most peptide users get wrong because population reference ranges are flat and IGF-1 itself drops sharply with age. An IGF-1 of 250 ng/mL is mid-range for a 25-year-old and well above the 97th percentile for a 65-year-old.

The lab ranges below are approximate and adapted from Quest Diagnostics and LabCorp reference data. Always interpret against the range printed on your own report, but use this as a sanity check on the numbers your lab gives you.

Timing relative to the last peptide dose matters too. For GH secretagogues, draw at least 12 hours after the last dose (24 hours preferred). For weekly GLP-1s, draw mid-week or just before the next injection for trough readings. For short-acting peptides like BPC-157 or GHRP-2, the morning trough before the day's first dose is the standard.

Some lab findings are non-negotiable stop signals regardless of how good you feel. These thresholds come from clinical trial monitoring rules and FDA-label adverse-event language. If your draw shows any of them, stop the protocol and talk to a clinician.

Peptide users have three real options for ordering blood work: ask a physician (gold standard, often the slowest), use a direct-to-consumer venipuncture service like Quest or LabCorp's self-pay portals, or use an at-home kit. Each makes sense in different situations.

SiPhox Health is PepPal's current pick for the at-home category. SiPhox uses an EasyDraw upper-arm collection device (not a finger prick), processes samples at a CLIA-certified lab, returns results in 5-10 days with built-in interpretation, and offers panels across cardiovascular, metabolic, hormonal, thyroid, liver, kidney, inflammation, and nutritional categories. Their GLP-1 panel is purpose-built for users on semaglutide or tirzepatide, and the Ultimate 360 panel runs up to 60 biomarkers across all the categories this guide recommends.

If you want standard blood-draw accuracy and your local Quest or LabCorp self-pay portal carries the markers you need, that is also a defensible choice. The most important thing is consistency — run the same panel from the same provider over time so you are tracking trends, not lab-to-lab variation.

Most peptide blood work guides treat every peptide the same. They are not the same. Three of the compounds people use — semaglutide, tirzepatide, and tesamorelin — are FDA-approved with detailed prescribing labels and Phase 3 trial data behind every monitoring recommendation. The rest are research-use compounds. The monitoring logic transfers, but the evidence behind it is weaker.