List of Injectable Peptides and What They Do

Injectable peptides are short chains of amino acids delivered by syringe, usually into subcutaneous fat, and they are used for very different purposes: appetite and blood sugar control, growth hormone signaling, tissue repair, immune modulation, and even skin tone. This list of injectable peptides and what they do groups the most commonly discussed molecules by category and notes whether each one is approved by the FDA. Most of these products require a prescription when they are legal at all, and none should be started without guidance from a licensed healthcare professional.

What Makes Something an Injectable Peptide

A peptide is a chain of amino acids shorter than a protein, generally under about 50 residues. Understanding polypeptide structure matters here, because sequence and shape decide whether a molecule behaves like a hormone, an enzyme fragment, or a simple signaling cue.

People often ask what is the monomer of a polypeptide, and the answer is the individual amino acid. Link a few dozen of those monomers in a specific order and you get the common polypeptide examples seen in medicine, such as insulin, glucagon, and GLP-1.

Shape matters too. Secondary structure, meaning a repeated pattern of coiling or folding within a polypeptide chain, is one reason a peptide can stay stable in a refrigerated vial but degrade in a warm car.

Metabolic and Weight-Loss Peptides

This is the largest and most commercially visible group. These peptides copy gut and pancreatic hormones that regulate appetite, insulin release, and stomach emptying.

• Semaglutide (Ozempic, Wegovy) — a GLP-1 receptor agonist injected weekly; FDA-approved for type 2 diabetes and chronic weight management.
• Tirzepatide (Mounjaro, Zepbound) — a dual GIP and GLP-1 receptor agonist injected weekly; FDA-approved for type 2 diabetes and chronic weight management.
• Liraglutide (Victoza, Saxenda) — a once-daily GLP-1 receptor agonist approved for diabetes and weight management.
• Pramlintide (Symlin) — an amylin analog injected with meals for diabetes.
• Insulin and insulin analogs — peptide hormones, and the original injectable peptide therapy.

Semaglutide, tirzepatide, and liraglutide are FDA-approved for chronic weight management under specific brand names. Common side effects across the GLP-1 class include nausea, vomiting, diarrhea, and constipation, and the prescribing labels carry warnings about pancreatitis and gallbladder problems.

Growth Hormone Secretagogues

These peptides prompt the pituitary gland to release more growth hormone. They are heavily marketed in fitness and anti-aging circles, but only one is currently FDA-approved, and for a narrow use.

Peptide	Mechanism	Typical injection schedule	FDA status (US)
CJC-1295	GHRH analog	Daily or weekly, depending on the version	Not approved
Ipamorelin	Ghrelin receptor agonist	Daily	Not approved
Sermorelin	GHRH analog	Daily	Formerly approved; brand discontinued
Tesamorelin (Egrifta)	GHRH analog	Daily	Approved for HIV-associated lipodystrophy
Hexarelin	Ghrelin receptor agonist	Daily	Not approved

Reported side effects of growth hormone secretagogues include water retention, joint pain, tingling in the hands, and elevated blood sugar. Formulators who know how to calculate net charge of polypeptide at a given pH understand why these molecules are fragile: small changes in solution chemistry can alter how they fold and how long they hold up in storage.

Repair and Recovery Peptides

This category is dominated by two names that are popular online and unapproved in the United States.

• BPC-157 — a synthetic fragment studied in animals for tendon, ligament, and gut-lining repair. BPC-157 is not FDA-approved for human use in the United States, and human trials remain limited.
• TB-500 — a fragment of thymosin beta-4 studied in animals for wound healing. TB-500 is not FDA-approved for human use in the United States.
• Thymosin alpha-1 — an immune-signaling peptide approved in some countries as an adjunct therapy; it is not FDA-approved in the US.
• GHK-Cu — a copper-binding peptide used mainly in topical skin products; injectable versions are not approved.

Vials sold as research chemicals are not manufactured to pharmacy standards, and independent testing has repeatedly found mislabeled products and inconsistent purity. Dose accuracy is the difference between a therapeutic effect and a harmful one, which is why unverified sources carry real risk.

Cosmetic and Melanocortin Peptides

These peptides act on pigment or sexual-response pathways, and the group includes both an approved medicine and one of the most notorious unapproved products.

• Bremelanotide (Vyleesi) — FDA-approved for hypoactive sexual desire disorder in premenopausal women.
• Afamelanotide (Scenesse) — FDA-approved to reduce pain from sun exposure in erythropoietic protoporphyria.
• Melanotan I and II — sold online for tanning; neither is FDA-approved, and both have been linked to rapid mole changes, nausea, and blood pressure swings.
• Cosmetic pentapeptides — used topically for fine lines; injectable marketing claims have not been reviewed by the FDA.

FDA Status at a Glance

Peptide	Category	Commonly marketed for	FDA status (US)
Semaglutide	GLP-1 agonist	Diabetes, weight loss	Approved (prescription)
Tirzepatide	GIP/GLP-1 agonist	Diabetes, weight loss	Approved (prescription)
Liraglutide	GLP-1 agonist	Diabetes, weight loss	Approved (prescription)
Tesamorelin	GHRH analog	HIV-related fat distribution	Approved (prescription)
Bremelanotide	Melanocortin agonist	Low sexual desire	Approved (prescription)
CJC-1295, ipamorelin, hexarelin	GH secretagogues	Fitness, anti-aging	Not approved
BPC-157, TB-500	Repair peptides	Injury recovery	Not approved
Melanotan II	Melanocortin agonist	Tanning	Not approved

Compounded versions of popular peptides are a separate category from FDA-approved drugs. The FDA has warned that compounded semaglutide and tirzepatide are not approved, have not been reviewed for safety or effectiveness, and have been linked to dosing errors. State-licensed compounding pharmacies operate under stricter rules than online peptide vendors, and a not for human consumption label is a signal to stop.

Questions to Ask Before Using an Injectable Peptide

1. Is this peptide FDA-approved for my specific condition, or is it being used off-label?
2. Who manufactured it, and can the vial be traced to a licensed pharmacy?
3. What does the human evidence, rather than animal studies or forum posts, actually show?
4. What are the known side effects and interactions with my current medications?
5. What monitoring, such as blood work, will I need while using it?

A licensed healthcare professional can review your history, flag interactions, and explain whether a prescription product is appropriate. Anyone selling injectable peptides as a supplement or a guaranteed fix is selling something the FDA does not recognize as a drug or a dietary ingredient.

COMMON QUESTIONS

Frequently Asked Questions

Which injectable peptides are FDA-approved in the US?

Semaglutide, tirzepatide, liraglutide, insulin, pramlintide, tesamorelin, bremelanotide, and afamelanotide are FDA-approved prescription injectable peptides. Most other popular peptides, including BPC-157, TB-500, CJC-1295, ipamorelin, and Melanotan II, are not FDA-approved for human use in the United States.

Are injectable peptides legal to buy online?

It depends on the peptide. FDA-approved peptides are prescription drugs and cannot be legally sold without a prescription. Unapproved peptides are often sold as research chemicals with not-for-human-consumption labels, which means they have not been reviewed for safety, purity, or dosing.

Do injectable peptides build muscle?

Growth hormone secretagogues such as CJC-1295 and ipamorelin can raise growth hormone and IGF-1 levels, but studies showing meaningful muscle gain in healthy adults are limited. Reported risks include fluid retention, joint pain, carpal tunnel symptoms, and elevated blood sugar. Resistance training and adequate protein remain the best-supported ways to build muscle.