The Peptide Guide
The twelve most-talked-about research peptides. For each one: a plain-language description, its regulatory use status, the benefits people report, and the risks and common symptoms documented in the research.
Retatrutide
Description: A triple-hormone-receptor agonist (GIP, GLP-1 and glucagon) in large clinical trials for obesity and metabolic disease. Injected weekly.
Benefits: Trial weight loss that can exceed tirzepatide (24%+ reported), with strong glycaemic and cardiometabolic improvement in the incretin class.
Risks & common symptoms: Nausea, vomiting, diarrhoea and constipation, often at lower doses because of its potency; muscle-mass loss on aggressive titration; long-term safety unknown; very high counterfeit risk.
Tesamorelin
Description: A growth-hormone-releasing-hormone analogue studied for reducing visceral abdominal fat, with more published clinical-trial data than most peptides here. Injected subcutaneously.
Benefits: Documented reduction in deep abdominal fat, improved lipid profile, and preservation of lean mass.
Risks & common symptoms: Joint and muscle pain, peripheral oedema, tingling, injection-site reactions, elevated blood glucose. Not recommended in active malignancy; blood-sugar monitoring is a common precaution.
GHK-Cu
Description: A naturally occurring copper-binding tripeptide with decades of cosmetic-science research on skin appearance and hair. Used topically, and less commonly by injection.
Benefits: Skin regeneration, wound healing, collagen synthesis and hair-follicle support, mostly from topical evidence.
Risks & common symptoms: Well tolerated topically. Injectable use is far less studied; theoretical concerns include copper overload with high-dose long-term use and skin discolouration near injection sites.
MOTS-c
Description: A peptide encoded in mitochondrial DNA, studied in early research on exercise physiology and metabolism. Human data is thin. Injected subcutaneously.
Benefits: Reported improvements in insulin sensitivity, exercise capacity and metabolic energy, mostly from animal models.
Risks & common symptoms: Injection-site reactions, occasional flushing, transient blood-glucose changes. Long-term safety is not established; not appropriate for people with unstable diabetes without close medical supervision.
NAD+
Description: A coenzyme central to cellular energy metabolism that declines with age. Research explores precursors (NR, NMN) and repletion; it is a coenzyme rather than a true peptide.
Benefits: Reported energy and cellular-ageing support. Longevity claims run far ahead of the human evidence.
Risks & common symptoms: IV infusion can cause flushing, nausea, chest tightness and cramping if run too fast. NAD+ degrades readily, so a poorly stored product may be inactive.
BPC-157
Description: A synthetic peptide derived from a protective protein found in gastric juice, the internet's favourite “healing peptide.” The evidence base is overwhelmingly animal studies; robust human trials are lacking.
Benefits: Reported accelerated healing of tendon, ligament and muscle injury, gut-lining repair, and reduced inflammation around joints.
Risks & common symptoms: Injection-site reactions, mild nausea, dizziness and headache. No long-term human safety data, and quality varies dramatically between suppliers.
PT-141
Description: A melanocortin-receptor agonist that acts on the central nervous system to modulate sexual arousal. Injected subcutaneously on demand.
Benefits: Reported increase in sexual desire and arousal in both men and women, unlike PDE5 inhibitors that act on blood flow only.
Risks & common symptoms: Nausea (common, especially first use), flushing, headache, transient blood-pressure rise, and hyperpigmentation with repeated use. Not appropriate with cardiovascular disease or uncontrolled hypertension.
SS-31
Description: A mitochondria-targeting peptide taken through serious clinical development for rare mitochondrial disease. Real pharma science, which is exactly why grey-market interest follows it.
Benefits: Reported mitochondrial-function support, reduced oxidative stress, and potential cardiovascular or neurological benefit, from disease-specific trial data.
Risks & common symptoms: Injection-site reactions, headache and dizziness. Because clinical data is disease-specific, community dosing conventions are extrapolations rather than evidence-based.
TB-500
Description: A synthetic fragment of thymosin β-4, a naturally occurring protein involved in cell migration and repair. Like BPC-157, the excitement rests almost entirely on animal and lab studies.
Benefits: Reported faster soft-tissue recovery, improved flexibility, and reduced inflammation. Frequently stacked with BPC-157.
Risks & common symptoms: Injection-site reactions, transient lethargy and head-rush. Its documented pro-angiogenic effect (new blood-vessel growth) raises theoretical concern for anyone with a current or past cancer diagnosis.
KPV
Description: A three-amino-acid fragment of the natural hormone α-MSH, studied in early lab and animal research on inflammation, including gut models.
Benefits: Reported anti-inflammatory effects and gut-inflammation support in lab and animal models.
Risks & common symptoms: Little human safety data exists; the risk profile is essentially uncharacterised in humans. Injection-site reactions are reported.
Semax
Description: A synthetic analogue of a fragment of the hormone ACTH, developed in Russia and used there as a nasal spray. Discussed for focus, mental clarity and a cognitive “flow” state.
Benefits: Reported sharper focus, improved memory and mental stamina, and mood support. Most human data is Russian and not widely replicated.
Risks & common symptoms: Generally well tolerated in the small studies published; nasal irritation with the spray. Long-term safety outside Russian clinical use is essentially uncharacterised.
CJC-1295
Description: A synthetic growth-hormone-releasing hormone analogue. The “with DAC” form lasts about a week; “without DAC” (Mod GRF 1-29) is short-acting. Commonly paired with Ipamorelin. Injected subcutaneously.
Benefits: Reported increase in natural growth-hormone pulse, deeper sleep, improved training recovery, and gradual body-composition change over months.
Risks & common symptoms: Water retention, tingling in the extremities, transient flushing, headache and injection-site itching; a theoretical insulin-resistance risk with long-term growth-hormone elevation.