What Are Peptides? A Physician's Evidence-Aware Overview

Peptides are short chains of amino acids — essentially small proteins — that the body uses as chemical messengers to switch processes on and off. Some peptides are well-established, FDA-approved medicines (insulin and semaglutide are examples), while many others marketed for healing or longevity are supported mostly by animal and laboratory research. Understanding that difference is the single most important thing a patient can know before considering peptide therapy.

What Are Peptides, Exactly?

Proteins are long chains of amino acids folded into complex shapes. Peptides are shorter chains, usually between 2 and about 50 amino acids. Because they are small, many peptides act as signals rather than structural materials. They bind to receptors on cells and deliver instructions: release growth hormone, build new blood vessels, slow inflammation, produce collagen.

Your body makes thousands of peptides every day. Insulin, oxytocin, ghrelin and glucagon-like peptide-1 (GLP-1) are all peptides. Pharmaceutical science has learned to copy, stabilize and modify these natural signals, which is why peptide drugs now make up a meaningful share of modern medicine.

When patients ask me what peptides are, I find it helpful to separate them into three groups:

• FDA-approved peptide medicines — for example, semaglutide, tirzepatide, and tesamorelin. These have gone through large human trials for specific conditions.
• Peptides with approvals outside the U.S. — such as thymosin alpha-1, approved in many countries but not here.
• Investigational or research peptides — such as BPC-157 or TB-500, which have interesting preclinical data but limited human evidence and no FDA approval.

A Useful Framework: Three Common Biological Failures

Many chronic conditions share overlapping drivers. In my practice, I find it helpful to look at three of them, because they connect internal medicine with longevity medicine:

1. Chronic, low-grade inflammation. The body's alarm system stays partly switched on, contributing to vascular disease, joint problems and metabolic dysfunction.
2. Insulin resistance. Cells respond less efficiently to insulin, which pushes glucose and insulin levels up and drives weight gain, fatty liver and eventually diabetes.
3. Declining mitochondrial energy. The cell's energy-producing machinery becomes less efficient with age and inactivity.

This framework is a way to think, not a promise that any single compound fixes all three. Sleep, resistance training, aerobic fitness, nutrition and appropriate prescription medicines are still the most proven tools against each of these problems. Peptides, where they have a role at all, are layered on top of that foundation.

How Peptides Work: The Example of BPC-157

BPC-157 is a good example of both the promise and the limits of this field. It is a synthetic 15-amino-acid peptide based on a sequence found in a protective protein in human gastric juice. In animal studies, it appears to:

• Promote new blood vessel formation (angiogenesis) through the VEGFR2 and nitric oxide pathways
• Increase growth hormone receptor expression in tendon cells
• Speed fibroblast migration and more organized collagen deposition

Rodent studies report faster healing of tendons, muscles and the gut lining. Those findings are genuinely interesting. But the human evidence is limited to small, uncontrolled case series, and much of the animal work comes from a single research group. That is why I describe BPC-157 as "promising but unproven" rather than as a healing breakthrough. You can read a deeper review in BPC-157 Mechanism Explained.

What about cancer risk?

Earlier online material sometimes claims that repair peptides "cannot" cause cancer. That claim goes beyond the evidence. Because compounds like BPC-157 promote blood vessel growth, there is a reasonable theoretical concern in anyone with an active or recent cancer, and they are avoided in that setting. The honest answer is that long-term human safety data do not exist.

Do Peptides Have to Be Injected?

Many peptides are broken down by stomach acid and digestive enzymes, so injection under the skin is often the most reliable route. But the rule is not absolute. Semaglutide is available in an oral tablet that uses an absorption enhancer, and BPC-157 is unusually stable in gastric juice in laboratory studies. The appropriate route depends on the molecule, the target tissue and — most importantly — the quality of the evidence. Patients should be skeptical of any source that says one route is the "only" one that works for everything.

What About Peptide "Stacks"?

You will see peptides marketed in combinations — BPC-157 with TB-500, KPV or GHK-Cu, for example — with claims that the effects multiply. There is a plausible biological rationale for some combinations, because the compounds act on different pathways. However, almost no human studies have tested these combinations directly. More compounds also mean more variables, more cost and more potential for side effects or drug interactions.

The Regulatory Picture

The legal status of peptides has changed significantly in recent years. In 2023, FDA placed many popular peptides in a category that prevented pharmacies from compounding them. In April 2026, FDA removed 12 of those peptides from that category for further review, and in July 2026 an FDA advisory committee recommended several — including BPC-157 and TB-500 — for the list of substances pharmacies may use. FDA rulemaking is still pending, so as of this writing compounding of these peptides is not yet authorized. I explain the details in Understanding Compounding Pharmacy Regulations for Peptides.

How I Approach Peptides at Laeeq M.D.

At Laeeq M.D., peptide discussions start with internal medicine: a detailed history, medication review, physical findings and laboratory testing. Only after that do we discuss whether any peptide has a reasonable evidence base for a specific goal, what is known and unknown, and whether a legal, quality-controlled source exists. Dosing is always individualized and is never decided before an evaluation. Many patients learn that the most effective next step is not a peptide at all, but a correction in sleep, training, thyroid function, iron status or blood sugar control. Learn more about our peptide and longevity program.

Sources

• Gastric pentadecapeptide body protection compound BPC 157 and its role in accelerating musculoskeletal soft tissue healing — Gwyer D, et al. Cell and Tissue Research, 2019
• Certain Bulk Drug Substances for Use in Compounding that May Present Significant Safety Risks — U.S. Food and Drug Administration, updated 2026
• FDA Advisory Committee Recommends Adding BPC-157 to Compounding List — American Med Spa Association, 2026

Book a Consultation

If you are curious whether peptides have a place in your health plan, the best first step is a careful medical evaluation rather than a product. Dr. Laeeq offers 60-minute consultations, virtually or in person in Reston, VA, for patients in Virginia, Maryland, Florida, Texas, California, Pennsylvania and Tennessee. Book a consultation to review your history, labs and goals.

This article is for educational purposes and is not medical advice. Discuss any treatment with a licensed physician who knows your history.