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Retatrutide (Reta)

Peptidesubcutaneous · inferred

Triple hormone receptor agonist targeting GIP, GLP-1, and glucagon receptors simultaneously. Half-life of ~6 days enables once-weekly dosing. Phase 2 trials showed up to 24% body weight reduction at 48 weeks, the highest of any anti-obesity agent tested to date.

Projected serum levels — 4 mg, weekly

Retatrutide (Reta)
Retatrutide (Reta) modeled serum levels, 4 mg weekly over 49 days Population-based pharmacokinetic estimate. Steady state reached after approximately 21 days. 0 1.3 2.5 3.8 5 Day 0 Day 12 Day 25 Day 37 Day 49 Time on a regular schedule ≈ steady state · day 21
Retatrutide (Reta) modeled serum levels with a loading dose of 8.7 mg, then 4 mg weekly The first dose is larger so levels approach steady state faster. 0 1.3 2.5 3.8 5 Day 0 Day 12 Day 25 Day 37 Day 49 Time on a regular schedule

Maintenance schedule: 4 mg weekly (subcutaneous).

Loading schedule: 8.7 mg on day 1, then 4 mg weekly — reaching therapeutic levels sooner.

Modeled steady state after ~21 days: peak ≈ 3.9 mg, trough ≈ 2.7 mg body load. Population-based estimate over 49 days for a 4 mg dose at a 70 kg reference body mass — the interactive app scales curves to your doses, timing, and body mass.

Key facts

Category
Peptide
Route modeled
Subcutaneous
Model confidence
inferred
Half-life
6 days
Common dose
4 mg
Suggested maximum
12 mg/day
Reference dose range
2–12 mg (single dose)
Suggested cadence
weekly
Validated against
12 mg sc — Cmax 0.55 mg/L at 48 h

Documented interactions

  • danger
    Levothyroxine (Synthroid) + Retatrutide (Reta) Protein binding

    Retatrutide (Reta) may displace Levothyroxine (Synthroid) from plasma protein binding sites, transiently raising free drug concentration. This drug has a narrow therapeutic index; free concentration…

  • danger
    Tacrolimus (Prograf) + Retatrutide (Reta) Protein binding

    Retatrutide (Reta) may displace Tacrolimus (Prograf) from plasma protein binding sites, transiently raising free drug concentration. This drug has a narrow therapeutic index; free concentration…

  • danger
    Warfarin (Coumadin) + Retatrutide (Reta) Protein binding

    Retatrutide (Reta) may displace Warfarin (Coumadin) from plasma protein binding sites, transiently raising free drug concentration. This drug has a narrow therapeutic index; free concentration…

  • warning
    Apigenin + Retatrutide (Reta) Protein binding

    Apigenin may displace Retatrutide (Reta) from plasma protein binding sites, transiently raising free drug concentration.

  • warning
    Aripiprazole (Abilify) + Retatrutide (Reta) Protein binding

    Aripiprazole (Abilify) may displace Retatrutide (Reta) from plasma protein binding sites, transiently raising free drug concentration.

  • warning
    Armour Thyroid (Desiccated Thyroid Extract) + Retatrutide (Reta) Protein binding

    Retatrutide (Reta) may displace Armour Thyroid (Desiccated Thyroid Extract) from plasma protein binding sites, transiently raising free drug concentration.

Serum checks 143 modeled interaction pairings for retatrutide (reta) across your whole stack — absorption conflicts, enzyme inhibition, and nutrient depletion included.

Research behind this entry

  1. Triple-Hormone-Receptor Agonist Retatrutide for Obesity - A Phase 2 Trial Jastreboff AM et al. · New England Journal of Medicine, 2023 DOI

    Phase 2 dose-finding trial in 338 adults with obesity showing retatrutide produced dose-dependent weight loss up to 24.2% at 48 weeks, exceeding results of all prior anti-obesity medications.

  2. Triple hormone receptor agonist retatrutide for metabolic dysfunction-associated steatotic liver disease: a randomized phase 2a trial Sanyal AJ et al. · Nature Medicine, 2024 DOI

    Phase 2a trial demonstrating retatrutide significantly reduced liver fat content in patients with MASLD, with normalization of liver fat in the majority of treated patients.

  3. The novel GIP, GLP-1 and glucagon receptor agonist retatrutide delays gastric emptying Urva S et al. · Diabetes, Obesity and Metabolism, 2023 DOI

    Demonstrated retatrutide delays gastric emptying through GLP-1 receptor activation, contributing to its appetite-suppressing and weight loss effects.

3 published studies referenced in the app, each with a plain-language summary.