Best Peptides for Weight Loss (2026)

Peptides influence weight loss through several distinct biological mechanisms, depending on the class of compound. Understanding these mechanisms helps clarify why different peptides are suited to different aspects of metabolic health.

GLP-1 receptor agonists (tirzepatide, retatrutide, semaglutide) work primarily by mimicking the incretin hormone GLP-1. This slows gastric emptying, reduces appetite at the hypothalamic level, and improves insulin sensitivity. The result is reduced caloric intake and improved metabolic efficiency.

Growth hormone secretagogues and GHRH analogs (tesamorelin, sermorelin, ipamorelin) stimulate natural growth hormone release from the pituitary. GH promotes lipolysis (fat breakdown) and helps preserve lean tissue during caloric restriction — a key challenge in any weight loss protocol.

GH fragments (AOD-9604) isolate the fat-metabolizing portion of growth hormone, targeting lipolysis directly without the broader hormonal effects of full GH therapy.

It's important to note that no peptide replaces the fundamentals of energy balance. Research consistently shows that peptides work best as an adjunct to proper nutrition and physical activity, not as a standalone solution.

Selecting a peptide for weight loss research depends on several factors:

• Magnitude of weight loss needed: GLP-1 agonists like retatrutide and tirzepatide show the most dramatic results (15–25% body weight) in clinical trials. If significant fat loss is the primary goal, these are the most well-supported options.
• Visceral fat vs. overall fat: Tesamorelin is specifically researched for visceral fat reduction and has FDA approval for this indication. If visceral fat is the primary concern, tesamorelin has the strongest targeted evidence.
• Preserving lean mass: GHRH analogs like sermorelin and ipamorelin stimulate GH, which helps maintain muscle during a caloric deficit. These may be worth exploring for those prioritizing body composition over pure scale weight.
• Minimal hormonal impact: AOD-9604 is designed to promote fat metabolism without affecting IGF-1, blood sugar, or other growth hormone pathways, making it a lower-intervention option.

Always discuss any peptide protocol with a healthcare provider, particularly if you have existing metabolic conditions, are taking medications, or have a history of thyroid disorders or pancreatitis.

Each peptide class carries its own safety profile:

GLP-1 agonists commonly cause nausea, vomiting, diarrhea, and constipation, particularly during dose escalation. These effects typically diminish over 4–8 weeks. More serious but rare risks include pancreatitis and gallbladder issues. GLP-1 agonists are contraindicated in patients with a personal or family history of medullary thyroid carcinoma or MEN2 syndrome.

GHRH analogs and GH secretagogues can cause water retention, joint pain, numbness/tingling, and elevated blood sugar. Long-term GH elevation may carry theoretical risks related to cell proliferation, though stimulating natural GH production (vs. injecting exogenous GH) maintains physiological feedback loops.

AOD-9604 has shown a favorable safety profile in clinical studies, with no significant adverse effects reported beyond mild injection site reactions. Its GRAS status from the FDA reflects its safety at studied doses.

Quality and sourcing matter significantly. Research peptides should come from reputable sources that provide third-party certificates of analysis (COAs) confirming purity and identity. Contaminated or degraded peptides can cause unpredictable adverse effects. See our guide on how to store peptides to ensure product integrity.

One of the biggest developments in the GLP-1 space is the arrival of oral semaglutide for weight management. With the FDA approval of oral Wegovy in January 2026, patients now have a genuine choice between taking a daily pill or a weekly injection for GLP-1-based weight loss.

Oral GLP-1 Options

• Rybelsus (oral semaglutide 3–14 mg): FDA-approved for type 2 diabetes. The original oral GLP-1 agonist, available since 2019. Uses SNAC absorption enhancer technology to survive stomach acid.
• Oral Wegovy (oral semaglutide 25–50 mg): FDA-approved January 2026 for chronic weight management. Higher doses designed specifically for obesity treatment. The OASIS-1 trial showed 15.1% body weight loss — matching injectable Wegovy results.

Injectable GLP-1 Options

• Wegovy/Ozempic (injectable semaglutide): Once-weekly injection, 14.9% weight loss in STEP 1. The current standard of care for GLP-1 weight management.
• Mounjaro/Zepbound (tirzepatide): Once-weekly dual GLP-1/GIP agonist injection. 20–25% weight loss in SURMOUNT trials — superior to semaglutide in head-to-head comparisons.
• Saxenda (liraglutide): Daily GLP-1 injection. ~8% weight loss — less effective but longer safety track record (LEADER trial).

Oral vs Injectable: Pros and Cons

Factor	Oral	Injectable
Needle required	No	Yes (auto-injector pen)
Dosing frequency	Daily	Weekly (or daily for liraglutide)
Empty stomach required	Yes (30-min fast)	No
Bioavailability	~1%	~89%
Absorption consistency	Variable	Predictable
Storage	Room temperature	Refrigerated
Travel convenience	Easier (no needles/cold chain)	Requires planning
Compounded available	No	Yes ($150–500/mo)

For a comprehensive breakdown of the oral vs injectable decision including efficacy data, side effect comparisons, and a decision framework, see our dedicated oral vs injectable semaglutide guide.

For comparisons between different GLP-1 compounds (not just delivery methods), see tirzepatide vs semaglutide and semaglutide vs liraglutide. For a beginner-friendly overview, start with the GLP-1 beginner's guide.

The compounded peptide market — particularly for GLP-1 agonists like semaglutide and tirzepatide — has exploded in recent years, driven by the high cost and limited insurance coverage of FDA-approved weight loss medications. Understanding the differences between compounded and FDA-approved peptides is critical for anyone exploring these options.

What Are Compounded Peptides?

Compounded medications are prepared by compounding pharmacies that create customized formulations. For weight loss, the most commonly compounded peptides are semaglutide and tirzepatide, typically in injectable form. These are not manufactured by the brand-name pharmaceutical companies (Novo Nordisk or Eli Lilly) and are not FDA-approved products.

503A vs 503B Pharmacies

There are two types of compounding pharmacies, and the distinction matters significantly for quality and oversight:

• 503A pharmacies are state-licensed pharmacies that compound medications for individual patients based on a valid prescription. They are regulated by state boards of pharmacy with varying levels of oversight. Quality standards depend heavily on the individual pharmacy.
• 503B outsourcing facilities are FDA-registered and inspected facilities that can produce compounded drugs in larger batches. They must follow current Good Manufacturing Practice (cGMP) guidelines and are subject to more rigorous quality standards, including sterility testing and potency verification.

The FDA's Position

The FDA has taken an increasingly aggressive stance on compounded GLP-1 medications:

• Semaglutide: In late 2024, the FDA declared the semaglutide shortage resolved, legally restricting compounding of semaglutide copies. Legal challenges from compounding pharmacies are ongoing as of early 2026.
• Tirzepatide: The FDA has also moved to restrict compounded tirzepatide, with Eli Lilly actively pursuing enforcement actions against compounders.
• Warning letters: Multiple warning letters have been issued to compounders, and some products have been seized.
• Salt form controversy: Some compounders produce "semaglutide sodium" (a salt form) rather than semaglutide base, arguing it is a different chemical entity. The FDA disputes this interpretation.

Quality and Safety Considerations

• Potency variability: FDA testing has found compounded semaglutide products with potency ranging from well below to well above the stated dose — meaning patients may receive unpredictable amounts of active drug.
• Sterility risks: Injectable products must be sterile. While 503B facilities have stronger sterility oversight, contamination incidents in the broader compounding industry (e.g., the 2012 New England Compounding Center meningitis outbreak) highlight the risks of inadequate quality control.
• No FDA approval or bioequivalence: Compounded products have not been evaluated by the FDA for safety, efficacy, or bioequivalence. They may behave differently than the brand-name product in the body.
• No standard adverse event reporting: Unlike FDA-approved drugs, compounded products lack mandatory adverse event reporting systems.

What to Look For

If considering compounded peptides for weight loss:

• Use only 503B outsourcing facilities when possible — check the FDA's list of registered outsourcing facilities
• Request a Certificate of Analysis (COA) for each batch, showing identity, potency, sterility, and endotoxin testing
• Verify the pharmacy is properly licensed in your state
• Discuss with your healthcare provider — they can help evaluate the source and monitor your response

For more information on quality and storage, see our guides on how to store peptides and how to reconstitute peptides.

Cost is often the deciding factor when choosing a weight loss peptide. The gap between FDA-approved brand-name medications and compounded alternatives can be enormous — but so are the differences in quality assurance, insurance eligibility, and legal certainty.

Monthly Cost Comparison

Product	Type	Monthly Cost (List Price)	With Insurance/Savings
Wegovy (semaglutide 2.4 mg injection)	FDA-approved	~$1,350	$0–25 with savings card
Oral Wegovy (semaglutide 50 mg tablet)	FDA-approved	~$1,000–1,300	TBD (new approval)
Ozempic (semaglutide injection, diabetes)	FDA-approved	~$935	$25 with savings card
Rybelsus (oral semaglutide, diabetes)	FDA-approved	~$935	$10 with savings card
Mounjaro/Zepbound (tirzepatide injection)	FDA-approved	~$1,060–1,200	$0–25 with savings card
Compounded semaglutide (injection)	Compounded	$150–500	Not insurance-eligible
Compounded tirzepatide (injection)	Compounded	$200–600	Not insurance-eligible
AOD-9604	Research peptide	$50–150	Not insurance-eligible

Insurance Coverage Landscape (2026)

• Commercial insurance: Most plans cover Ozempic/Rybelsus for diabetes with prior authorization. Wegovy/Zepbound coverage for obesity is expanding but not universal. Many plans require BMI ≥30 (or ≥27 with comorbidities) and step therapy (trying lifestyle changes first).
• Medicare Part D: Currently excludes most anti-obesity medications. The Treat and Reduce Obesity Act (TROA) has been reintroduced in Congress to change this, but has not passed as of early 2026. Diabetes indications (Ozempic, Mounjaro) are covered.
• Medicaid: Coverage varies by state. Some state Medicaid programs cover GLP-1s for obesity; many do not.
• Employer self-insured plans: Increasingly covering GLP-1s for weight management. Large employers (especially in healthcare, tech, and finance) are leading adoption.

Strategies to Reduce Cost

• Manufacturer savings programs: Novo Nordisk and Eli Lilly offer savings cards that can reduce copays to $0–25/month for commercially insured patients.
• Prior authorization: Work with your provider to submit thorough prior authorization documentation, including BMI, comorbidities, and documentation of prior weight loss attempts.
• Diabetes indication: If you have type 2 diabetes or pre-diabetes, GLP-1 medications may be covered under the diabetes indication even if weight loss coverage is denied.
• Patient assistance programs: Both Novo Nordisk and Eli Lilly offer programs for uninsured patients meeting income criteria.

For a more detailed look at GLP-1 costs and insurance navigation, see the GLP-1 beginner's guide. For peptide stacks that may offer alternative approaches, see the weight loss stack and fat loss stack guides.