Types of Peptide Therapy

The word "peptides" gets used as though it describes one thing, when it really describes a category in the same way that "antibiotics" describes a category. The peptide that helps someone lose forty pounds has almost nothing in common with the one someone else uses for skin repair.

That distinction matters, because the useful question isn't whether to try peptides. It's which signal you're trying to send, and which peptide sends it.
Below is what each of the main types of peptide therapy does, who it tends to suit, and how to tell them apart.

What a peptide actually is and how peptide therapy works

A peptide is a short chain of amino acids that occurs naturally in the human body. Your body produces thousands of these endogenous messengers, and they help regulate processes like cell metabolism, immune function, and tissue repair by delivering precise instructions to your cells: repair this tissue, release that hormone, slow down, wake up. Think of peptides like Uber, but for your cells, delivering exact messages to the right place at the right time.

This messaging system grows quieter with age. Growth hormone output declines, collagen synthesis slows, and appetite and satiety signaling drift out of calibration. Peptide therapy reintroduces specific signals, either natural peptides or synthetic ones designed to mimic them, so the body does something it already knows how to do, only more reliably.

This is why the type of peptide matters so much. You are not taking a general-purpose supplement; you are choosing a specific message.

Type 1: GLP-1 peptides, for appetite and metabolic control

GLP-1, or glucagon-like peptide-1, is a hormone your gut releases after you eat. It tells your brain you're full, slows how quickly your stomach empties, and helps regulate blood sugar.

GLP-1 peptide therapy amplifies that signal. Semaglutide is a common GLP-1 example, and tirzepatide is another popular weight-loss peptide used to support appetite and blood sugar control. In practice, people tend to describe two effects. The first is physical, a sense of fullness that arrives sooner and lasts longer. The second is the quieting of what's often called food noise, meaning the background mental chatter about the next meal or the snack drawer. For a lot of people, that second effect is the one that changes their week.

This type tends to suit:

• Weight that plateaus despite consistent effort
• Constant preoccupation with food between meals
• Insulin resistance or blood sugar dysregulation
• Anyone who has lost weight before and regained it

Dosing is titrated upward gradually rather than started at the target dose. That's deliberate, because gradual escalation is how gastrointestinal side effects are kept manageable. Many peptide drugs degrade in the digestive tract when taken orally, which is why peptide injections and other injectable peptides are common in this category. Progress should be measured in months rather than weeks.

One honest caveat is worth stating plainly. GLP-1 therapy isn't a standalone fix. Without adequate protein intake and resistance training, a meaningful share of the weight lost will be lean mass rather than fat. Any program that doesn't raise this with you at the outset isn't managing you properly.

Type 2: Dual GIP and GLP-1 peptides, the two pathway version

GIP, or glucose-dependent insulinotropic polypeptide, is a second gut hormone that works alongside GLP-1. A dual agonist activates both receptors at once rather than one.

The practical difference is that two pathways of appetite and metabolic signaling are engaged instead of a single one. Clinically, dual agonists have generally produced greater average weight reduction than single pathway GLP-1 therapy, and some people tolerate them better. GIP activity appears to moderate some of the nausea associated with GLP-1 alone, although this varies considerably from person to person.

This type tends to suit:

• People who have stalled on a single pathway GLP-1
• Higher BMI starting points, where a larger total reduction is the goal
• Strong, persistent cravings that GLP-1 alone hasn't touched
• Anyone prioritizing maximum result under close supervision

Neither option is universally superior, and starting on the stronger one isn't automatically the better call. The right choice depends on your starting metabolic picture, your history with these medications, how well you tolerate titration, and cost. This is exactly the conversation to have with a prescriber who will follow you month to month.

Type 3: Growth hormone secretagogues, sermorelin for recovery and sleep

Sermorelin works differently from the metabolic peptides above. It doesn't replace growth hormone. It's a growth hormone-releasing hormone analog, which means it prompts your own pituitary to release growth hormone in your body's natural pulsatile rhythm.

That distinction is the whole point. Because release stays under the control of your existing feedback loops, the physiology remains closer to normal than it does with direct hormone administration.

Research suggests that growth hormone secretagogues may support body composition, recovery, sleep quality, bone density, and energy, and sermorelin is generally well tolerated. These are supportive findings rather than guarantees, and results vary meaningfully between individuals.

This type tends to suit:

• Age-related loss of muscle despite continued training
• Poor sleep quality, particularly trouble reaching deep sleep
• Recovery between sessions that has slowed with age
• Persistent low energy without a clear underlying cause

Sermorelin works more slowly than GLP-1 therapy. Sleep quality is often the first thing people notice, sometimes within a few weeks, while body composition changes take months of consistency. This is a long game protocol rather than a quick correction.

Type 4: Copper peptides, GHK-Cu for skin and tissue repair

GHK-Cu is a naturally occurring copper-binding peptide found in human plasma. Its concentration drops substantially with age, which makes it one of the clearest illustrations of the signal loss described earlier, and GHK-Cu is often discussed as a copper peptide used in skin rejuvenation because it may stimulate collagen and elastin production.

Research suggests that GHK-Cu may support collagen production, skin firmness, and the body's natural tissue repair processes, with possible benefits for skin health partly through support of the skin barrier and visible firmness. It's sometimes called the glow peptide for that reason.
Collagen peptides taken orally, including hydrolyzed collagen, are usually discussed separately from GHK-Cu because they fall under dietary supplements rather than the same peptide therapy approach.

This type tends to suit:

• Fine lines, loss of firmness, and dull skin tone
• Skin that heals slowly
• Age-related collagen decline
• Anyone wanting an aesthetic or repair-focused addition to a broader protocol

GHK-Cu is rarely the whole plan. It most often runs alongside a metabolic or longevity protocol, addressing the visible layer while another peptide does the underlying work.

How to tell which type you need

The simplest approach is to name the outcome you want before you name the compound.

If two rows of that table apply to you, that's entirely normal, and it's a good reason to speak with a clinician rather than picking one and hoping. Peptides are frequently combined, but combinations need to be sequenced properly. Starting several at once makes it impossible to tell what's working, what's causing a side effect, and what you could drop.

Book a free consultation to find the best peptide for you.

The part that matters more than the peptide

One version of peptide therapy involves a vial from an unmarked website and a dosing chart copied from a forum. Another involves a prescription, a titration schedule, and a clinician who checks in each month. The molecule in the vial can be identical in both cases, but the outcomes usually aren't.

What separates them:

• A licensed provider prescribing the protocol after reviewing your labs, history, and current medications
• Titration, so that the target dose is built up 
• Regular check-ins, so that a side effect gets addressed in week three instead of month three
• Someone willing to stop the protocol if it isn't working, which is the step self-directed users almost never take

At Onus, every protocol is prescribed by Nurse Practitioners with monthly check-ins built into the plan. You can see the full range of medically supervised peptide protocols and pricing here.
 

Where to start

Decide on the outcome first. Then have someone qualified tell you whether a peptide is the right tool for reaching it, including the possibility that it isn't.

Book a free consultation with our medical team and we'll work out which protocol, if any, actually fits what you're trying to do.