Side-by-side · Research reference

RetatrutidevsSS-31

Side-by-side comparison across mechanism, dosage, evidence, side effects, administration, and stack synergies. Citations on every claim where available.

APhase 2Reviewed10/41 cited

BPhase 3Reviewed9/43 cited

Retatrutide

Triple-receptor agonist · Phase 3

1–12 mgWeekly doseJastreboff 2023

24.2%Body-weight ↓Jastreboff 2023

~6 daysHalf-life (est)

SQ · Abdomen · Once weekly

SS-31

Cardiolipin-binding · Mitochondrial protective

40 mgDaily doseSzeto 2014

Phase 3Evidence levelSzilagyi 2009 Szeto 2014

~3 hrHalf-life

SQ · Abdomen · Once daily

01Mechanism of Action

Parameter

Retatrutide

SS-31

Primary target

GLP-1R + GIPR + Glucagon receptor (triple agonism)Jastreboff 2023

Cardiolipin in inner mitochondrial membraneSzeto 2014

Pathway

Triple-receptor activation → ↑insulin (GLP-1+GIP), ↓gastric emptying, ↑lipid handling, ↑energy expenditure (glucagon component)Jastreboff 2023

Cardiolipin binding → cristae stabilisation → ETC integrity → reduced ROS + preserved ATP synthesisSzeto 2014 Szilagyi 2009

Downstream effect

Maximal weight loss across class. Glucagon component drives lipolysis and energy expenditure beyond GLP-1+GIP aloneJastreboff 2023

Mitochondrial bioenergetic preservation; cardio-, neuro-, and reno-protective effects in animal + clinical studiesSzeto 2014

Feedback intact?

—

Origin

Synthetic peptide engineered for balanced affinity at three incretin / glucagon receptorsJastreboff 2023

Synthetic tetrapeptide D-Arg-Dmt-Lys-Phe-NH₂; cell-permeable, mitochondrial-selectiveSzeto 2014

Antibody development

—

02Dosage Protocols

Parameter

Retatrutide

SS-31

Standard dose

12 mg / week (max efficacy)Jastreboff 2023

Phase 2 trial dose. Phase 3 dosing TBD.

40 mg / day SQ (clinical trials)Szeto 2014

Anecdotal community range 5-10 mg/day. Phase 3 trials use 40 mg.

Frequency

Once weekly

Once daily

Titration schedule

2 mg → 4 mg → 8 mg → 12 mg over 16 weeks

—

Evidence basis

Phase 2 trial; Phase 3 ongoingJastreboff 2023

Multiple Phase 3 trials (Barth, AMD, ischemia-reperfusion)Szeto 2014 Szilagyi 2009

Duration

Indefinite for chronic indication (presumed)

Indefinite for mitochondrial disease; cycled for healthspan use

Reconstitution

Investigational; not commercially available

Bacteriostatic water

Timing

Any time of day

Morning fasted preferred; pre-workout for exercise-induced mitochondrial stress

Half-life

~6 days (estimated from class)

~3 h plasma; tissue uptake longer

Lower / starter dose

—

5 mg / day (anecdotal)

04Side Effects & Safety

Parameter

Retatrutide

SS-31

GI symptoms

Nausea, vomiting, diarrhea (very common, dose-dependent)Jastreboff 2023

Nausea (uncommon)

Heart rate

↑ resting HR (3–7 bpm at 12 mg)Jastreboff 2023

—

Glucose handling

Glycemic improvement; rare hyperglycemia from glucagon component

—

Pancreatitis risk

Class warning

—

Thyroid C-cell tumours

Class warning (presumed)

—

Pregnancy / OB

Avoid (insufficient data)

Avoid — insufficient data

Injection site reaction

—

Erythema, mild pruritus

Headache

—

Reported in some Phase 3 trials

Cardiovascular

—

Cardio-protective in studies; no signal of harm

Long-term safety

—

Phase 3 data over 24+ months; no major safety signalsSzeto 2014

Absolute Contraindications

Retatrutide

·MTC personal or family history (presumed class effect)
·Pregnancy / breastfeeding

SS-31

·Pregnancy / breastfeeding
·Hypersensitivity to peptide

Relative Contraindications

Retatrutide

·Severe gastroparesis
·History of pancreatitis
·Severe cardiovascular disease (HR signal)

SS-31

·None established

05Administration Protocol

Parameter

Retatrutide

SS-31

1. Reconstitution

Investigational peptide. Research vials reconstituted with bacteriostatic water per label.

Add bacteriostatic water per label. Light-protected handling.

2. Injection site

SQ — abdomen, thigh, or upper arm. Rotate weekly.

SQ — abdomen or thigh. Rotate sites.

3. Timing

Once weekly, same day.

Morning fasted; pre-workout for exercise-augmented mitochondrial stress.

4. Storage

Refrigerate 2–8 °C. Light-protected.

Lyophilised: refrigerate, light-protected. Reconstituted: refrigerate ≤30 days.

5. Needle

27–31G, 4–8 mm insulin syringe.

29–31G, 4–8 mm insulin syringe.

06Stack Synergy

Retatrutide

— no documented stacks

SS-31

+ MOTS-c

Moderate

View MOTS-c →

SS-31 and MOTS-c address mitochondrial decline through complementary axes. SS-31 protects existing mitochondrial structure (cardiolipin binding, cristae stabilisation). MOTS-c upregulates AMPK/PGC-1α, triggering biogenesis of new mitochondria. Together they pair preservation with renewal — anecdotally favoured in healthspan and post-cardio-event recovery protocols.

SS-31: 5–10 mg SQ · daily morning
MOTS-c: 5 mg SQ · 2× per week pre-workout
Primary benefit: Mitochondrial preservation + biogenesis