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Plain-English comparison

GLP-1 peptides compared in plain English

How semaglutide, tirzepatide, liraglutide, and investigational retatrutide differ in targets, evidence, and approval status.

By the PeptideFactSheets Editorial Team. Claims are source-checked under our editorial policy; clinician review is identified only when a named reviewer is shown.

The quick overview

“GLP-1” is a useful family label, not a promise that every medicine works the same way. Liraglutide and semaglutide act at the GLP-1 receptor; tirzepatide acts at GIP and GLP-1 receptors; retatrutide is designed to act at GIP, GLP-1, and glucagon receptors.

Semaglutide, tirzepatide, and liraglutide appear in FDA-approved products for specific uses. Retatrutide remains investigational. Evidence and safety must be read at the product-and-indication level, not inferred from the family name.

Side-by-side comparison

Semaglutide
FDA approved for specific usesStrong human evidence for approved uses

Studied for

Type 2 diabetes · Chronic weight management · Cardiovascular outcomes

Tirzepatide
FDA approved for specific usesStrong human evidence for approved uses

Studied for

Type 2 diabetes · Chronic weight management · Obstructive sleep apnea in adults with obesity

Liraglutide
FDA approved for specific usesStrong human evidence for approved uses

Studied for

Type 2 diabetes · Chronic weight management · Cardiovascular outcomes

Retatrutide
In clinical trialsEarly human evidence

Studied for

Obesity and overweight · Type 2 diabetes · Cardiovascular and kidney outcomes

Approved versus investigational

An FDA approval means the agency reviewed evidence for a specific product, population, and use. It does not validate other molecules in the same family or uses outside the label. “In Phase 3” still means investigational.

What researchers are studying

  • Blood-sugar control in type 2 diabetes
  • Chronic weight management
  • Cardiovascular and kidney outcomes
  • Obesity-related conditions such as obstructive sleep apnea

Risks and reasons for caution

  • All can cause adverse effects; approved labels include medicine-specific warnings, contraindications, and use limitations.
  • A larger average change in one trial is not a head-to-head answer unless populations, study designs, duration, and endpoints are comparable.
  • Compounded or online products are not made equivalent merely by using the name of an approved active ingredient.

What remains uncertain

  • How every option compares head-to-head for long-term outcomes
  • Which results will extend to populations not represented in trials
  • The final benefit-risk profile and regulatory future of retatrutide

Questions to ask a healthcare professional

1. Which exact product and approved indication are we discussing?

2. What benefits were measured in people like me, and over what period?

3. Which warnings, interactions, or conditions change the risk?

4. What follow-up is needed to assess benefit and adverse effects?

Plain-English takeaway

The most important difference is not which name is newest. It is whether the exact product is approved for the exact use, what human evidence supports it, and how its risks fit a particular patient under licensed care.

References

  1. 1
    FDA: Drugs@FDA database

    Official source for approval records and current prescribing information.

  2. 2
    ClinicalTrials.gov

    U.S. National Library of Medicine registry of clinical studies.

  3. 3
    PubMed

    Peer-reviewed biomedical literature indexed by the National Library of Medicine.