A prescriber managing a compounded peptide course typically orders bloodwork before starting, then again at intervals afterward. What that panel usually includes is one question. What each result can and cannot tell a patient is a separate one, and it is worth separating from the sales pitch. This page walks through the labs that actually appear in sermorelin research, and the ones a prescriber might reasonably check that no sermorelin trial has ever touched.
IGF-1: the biomarker the whole drug is built around
Sermorelin does not supply growth hormone directly. It prompts the pituitary to release more of a patient’s own GH, which in turn raises insulin-like growth factor 1 (IGF-1) in the liver and elsewhere. In the one placebo-controlled adult trial, IGF-I rose significantly within two weeks of starting the drug (P < 0.05). IGFBP-3, a related binding protein, rose even more sharply (P < 0.001) [1]. A companion paper on the same cohort (n = 19) reported IGF-I up 28% in both sexes by four weeks, alongside growth hormone secretion itself rising 107% in men and 70% in women over the same window [2]. That trial ran on the 10 µg/kg nightly regimen covered in the dosage breakdown, which is the only adult dose with lab data of any kind behind it.
Here is the limit that matters most. IGF-1 moved in both men and women. The outcome buyers actually care about — lean body mass — moved in men only. Well-being and libido moved in men only. Sleep did not move in either sex [1]. A rising IGF-1 number confirms the pituitary responded to the drug. It does not confirm the response turned into something a person would notice, or a scan would detect. IGF-1 is a biomarker of GH-axis activity. It is not a stand-in for an outcome — a distinction covered in more depth in the IGF-1 testing breakdown.
Why a baseline draw matters
A single IGF-1 number, read without a baseline, tells you very little on its own. IGF-1 already varies by age, sex, and body composition before anyone starts a GHRH analog. A pre-treatment draw gives a personal reference point: a rise measured against your own starting value is more useful than a single reading compared to a general population range. The one adult trial used exactly this design — every participant was compared against their own baseline, not against each other [1].
Fasting glucose and insulin
The same trial recorded fasting insulin and glucose at every study visit. Those levels were reported as unaltered overall across 16 weeks of treatment. Insulin sensitivity, assessed separately by a glucose tolerance test, improved significantly in men (P < 0.05) but not in women [1]. That is a real, measured finding — in one small, short trial, in adults aged 55 to 71.
No published trial has measured HbA1c in sermorelin recipients at all. A PubMed search for sermorelin combined with HbA1c returns zero records. A broader search for sermorelin and glucose returns eleven records; beyond the trial above, none is a human sermorelin outcome study — the rest are animal metabolism papers or studies of unrelated GH-axis peptides. For longer-term glucose data in this drug class, the closest comparator is tesamorelin, a related but distinct GHRH analog that is FDA-approved. In a 12-month randomized trial of 60 obese adults, tesamorelin produced no significant effect on glucose, alongside a meaningful reduction in visceral fat [3]. That is tesamorelin data, not sermorelin data — context for the drug class, not evidence about sermorelin specifically.
Lipids: the one adverse finding on record
The adult trial’s own safety line is specific: the only adverse side effect was transient hyperlipidemia, which resolved by the end of the study [1]. That is the entire documented safety signal from the only controlled adult sermorelin trial. It is also the practical reason a prescriber might want a lipid panel, both before starting and partway through a course. See the full side-effects picture for how that finding fits alongside everything else reported.
Thyroid: an honest gap
No trial has measured thyroid function in people taking sermorelin. A PubMed search for sermorelin combined with thyroid returns seven records. Reading them, none is a human clinical study of thyroid function during sermorelin treatment — they cover a thyroid-cancer cell receptor study, a rat blood-flow experiment, and a study of GH response to a related peptide sorted by thyroid status, in rats. None of it is in people, and none of it is a sermorelin trial. A prescriber may still check thyroid-stimulating hormone as routine baseline screening before starting a hormone-adjacent therapy. That would be standard endocrine practice, not a finding sourced to sermorelin research.
What bloodwork cannot tell you
A lab value is not the same thing as a felt result. The clearest illustration sits inside the one trial covered here. IGF-1 rose in every participant, regardless of sex. The outcomes people actually want — more lean mass, better well-being — appeared in men only. Two people with an identical IGF-1 rise on paper had different real-world results in that trial. A number moving in the expected direction confirms the drug reached its target. It does not confirm anything past that.
A related point worth stating plainly: a lab panel cannot substitute for a prescriber reading the whole picture. Fasting glucose that looks unchanged on paper sat inside a trial where insulin sensitivity still improved, in men, on a separate test. One number rarely tells the whole story on its own. A panel is a snapshot, taken on one morning, of a system that moves throughout the day and across weeks of treatment. Sellers whose intake process includes a real lab panel rather than a questionnaire alone are listed on the injections board.
The bottom line
The labs with real sermorelin data behind them are IGF-1, IGFBP-3, fasting glucose and insulin, and lipids. Even those come from one small, short, older-adult trial. HbA1c and thyroid function have never been studied in sermorelin users at all. Whatever a prescriber checks, a lab result answers “did the biology respond.” It does not answer “did it work.”