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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. Use the source links to verify status, evidence, risks, and unknowns; our editorial policyexplains the boundaries. Clinician review appears 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, even with a completed Phase 3 registry record and company-reported top-line results. 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 trialsModerate 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.

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References

  1. 1
    fdaFDA prescribing information: Wegovy

    Current semaglutide label covering approved weight, cardiovascular-risk, and MASH indications.

  2. 2
    fdaFDA prescribing information: Zepbound

    Current tirzepatide label covering chronic weight management and obstructive-sleep-apnea indications.

  3. 3
    fdaFDA prescribing information: Saxenda

    Current liraglutide label for chronic weight management in defined populations.

  4. 4
    clinical trialsClinicalTrials.gov: TRIUMPH-1

    Completed Phase 3 retatrutide registry record without posted ClinicalTrials.gov results.

  5. 5
    company releaseLilly: TRIUMPH-1 top-line results

    Company-provided Phase 3 top-line obesity results; not a peer-reviewed publication or FDA approval.

  6. 6
    pubmedRetatrutide Phase 2 obesity trial

    Peer-reviewed Phase 2 evidence for the investigational triple-agonist program.