Tirzepatide + Retatrutide Stack
Important: Retatrutide is not FDA-approved and remains investigational. Its Phase 3 TRIUMPH-1 trial completed in April 2026 (NCT05929066), with the broader TRIUMPH program still reporting out and no approval granted yet. Only tirzepatide (Mounjaro/Zepbound) has FDA approval. No clinical trial has studied the two together, so everything below is community-reported rather than trial-established.
Retatrutide hits three receptors at once: GLP-1, GIP, and glucagon (Jastreboff AM et al. 2023, NEJM, PMID 37366315). Users report losing 30-50 lbs over roughly 24 weeks if they follow the tables and don't skip training, though again, no trial has looked at the combination. For some context, retatrutide on its own at 12 mg produced about 24.2% body-weight loss at 48 weeks (Jastreboff 2023, NEJM, PMID 37366315).
Some users say they prefer this to solo Tirzepatide. The glucagon part of retatrutide is linked to higher energy expenditure in preclinical work, but nothing proves the combination is actually better. Community reports also mention worse nausea in the first month, and there's no comparative tolerability data for the two together. You learn to adjust as you go.
Beginner Stack: Weeks 1-8
Start slow and let your body build tolerance. Tirzepatide's approved escalation begins at 2.5 mg and climbs through 2.5/5/7.5/10/12.5/15 mg once weekly, with 15 mg as the ceiling (Mounjaro US Prescribing Information, FDA, §2.1). Retatrutide's pharmacokinetics support once-weekly dosing (Coskun T et al. 2022, Cell Metabolism, PMID 35985340).
| Week | Tirzepatide Dose | Retatrutide Dose | Mixing | Tips |
|---|---|---|---|---|
| 1 | 2.5 mg | 0.5 mg | 1 ml + 0.1 ml | Watch for nausea. Eat small meals. |
| 2 | 2.5 mg | 0.5 mg | Same | Hydrate 3-4 L water daily. |
| 3 | 2.5 mg | 1 mg | 1 ml + 0.2 ml | Add electrolyte tabs if dizzy. |
| 4 | 5 mg | 1 mg | 2 ml + 0.2 ml | Up calories if energy low. |
| 5 | 5 mg | 1 mg | Same | Community reports ~2-4 lb loss (anecdotal). |
| 6 | 5 mg | 2 mg | 2 ml + 0.4 ml | Stomach settles here. |
| 7 | 7.5 mg | 2 mg | 3 ml + 0.4 ml | Split into 2 shots if volume high. |
| 8 | 7.5 mg | 2 mg | Same | Assess tolerance. |
If the nausea gets too rough, drop Retatrutide back to 0.5 mg for 2 weeks. Ginger tea helps, and Zofran 4 mg if you need it.
Intermediate Stack: Weeks 9-16
By now your stomach can handle more, so you can push for faster fat loss.
| Week | Tirzepatide Dose | Retatrutide Dose | Tips |
|---|---|---|---|
| 9 | 7.5 mg | 2.5 mg | 3 ml + 0.5 ml. Protein 1.6 g/kg bodyweight. |
| 10 | 10 mg | 2.5 mg | Switch to 10 mg vial. Energy up from glucagon. |
| 11 | 10 mg | 3 mg | 2 ml (5 mg/ml) + 0.6 ml. Walk 10k steps. |
| 12 | 10 mg | 3 mg | Same. Community-reported ~1-2 lb/week loss (anecdotal, not trial data). |
| 13 | 12.5 mg | 4 mg | Mix 2.5 ml (5 mg/ml) + 0.8 ml. |
| 14 | 12.5 mg | 4 mg | Monitor heart rate under 100 bpm resting. |
| 15 | 12.5 mg | 5 mg | Higher potency now. Loss tends to pick up. |
| 16 | 12.5 mg | 5 mg | Review progress. DEXA scan if possible. |
If your total volume goes over 3 ml, split the shots 4 hours apart on the same day.
Advanced Stack: Weeks 17-24+
Only move here if your side effects have stayed minimal. This is 15+ mg total weekly and not for beginners. Retatrutide's Phase 2 trial studied 1, 4, 8, and 12 mg once weekly, so the 8 mg below is a real studied dose, and a conservative one against the 12 mg maximum (Jastreboff 2023, NEJM, PMID 37366315).
| Week | Tirzepatide Dose | Retatrutide Dose | Total mg | Management |
|---|---|---|---|---|
| 17 | 12.5 mg | 6 mg | 18.5 | Creatine 5 g daily for muscle. |
| 18 | 15 mg | 6 mg | 21 | 3 ml (5 mg/ml Tirz) + 1.2 ml. |
| 19+ | 15 mg | 8 mg | 23 | Top of this protocol (Phase 2 max was 12 mg). Cycle off every 12 weeks? |
For maintenance once you hit your goals, users anecdotally run 5 mg Tirz + 2 mg Ret weekly. Keep in mind that long-term safety and maintenance for the combination are unstudied.
Injection Tips
- Site: 2 inches from navel. Alternate sides each week.
- Needle: 30-31G, 5/16 inch.
- Time: Sunday night. Fast 12 hours after shot.
- Draw order: Tirzepatide first (acidic). Then Retatrutide.
- Lump forms? Massage 5 min. Ice 10 min.
If your gut is still struggling, add BPC-157 calculator 250 mcg daily subQ.
Side Effects
Nausea is worst during weeks 2-6. With tirzepatide, GI events show up mostly during dose escalation and are usually mild to moderate (Jastreboff 2022, NEJM, PMID 35658024). The combination itself has no formal data. A few things that help:
- Inject night before bed.
- Glucose spikes? Metformin 500 mg with meals.
- Retatrutide diarrhea: Imodium (loperamide) 2 mg per dose as needed. Diarrhea is a documented retatrutide GI effect (Jastreboff 2023, NEJM, PMID 37366315).
- Wiped out? 200 mg caffeine + 5 g creatine.
- Bound up? Miralax 17 g daily.
Bloodwork every 8 weeks. HbA1c < 5.7%. Check lipids, kidneys.
Diet + Training
Dial this part in and 1-2 lbs/week comes off steadily.
- Calories: 20% deficit. 2 g protein per lb lean mass.
- Carbs: 100-150 g around workouts.
- Lift 4x/week, 45 min sessions. 20 min cardio after.
- Day looks like: Eggs + oats AM. Chicken salad lunch. Steak + veg dinner.
For extra fat burn, try AOD-9604 calculator 300 mcg in the mornings.
Cycling
Run 24 weeks on, then 4-8 weeks off at half dose. Some users anecdotally stay on 5 mg Tirz + 2 mg Ret long-term, but long-term safety and maintenance for the combination are unstudied.
If you run into supply problems, switch to Semaglutide calculator 1 mg weekly equivalent.
Peptide Add-Ons
These doses match common community protocols (and this site's other guides), but they have no trial support in this stacking context. Treat them as community-reported rather than evidence-based.
- CJC-1295 / Ipamorelin calculator: 100 mcg each before bed. Keeps muscle.
- GHK-Cu calculator: 1 mg subQ M/W/F. Tightens skin.
- HGH? Wait 12 weeks. 2 IU daily max.
| Add-On | Dose | Timing | Benefit |
|---|---|---|---|
| CJC/Ipa | 100/100 mcg | Bedtime | Muscle retention |
| GHK-Cu | 1 mg | M/W/F | Collagen + fat loss |
| MOTS-c | 5 mg | Weekly | Mitochondrial energy |
Troubleshooting
- Zero hunger: Force 1500 cal minimum. Try Ipamorelin calculator solo.
- Stuck losing: Bump Retatrutide 1 mg. Cut 500 cal more.
- Shots sting: Fresh vial. Room temp water.
- Shedding hair: Biotin 5 mg + minoxidil topical.
Results Timeline
These are community-reported ranges, not from any trial of this combination:
Week 4: 4-8 lbs gone. Pants loose.
Week 12: 15-25 lbs. Abs show if you started heavy.
Week 24: 30-50 lbs total. Body recomp.
Community reports put women around 20-40 lbs and men around 40-70 lbs at the top end. These sex-specific totals are anecdotal and don't appear in any published source. The only trial anchor is retatrutide on its own at about 24.2% body-weight loss at 48 weeks at 12 mg (Jastreboff 2023, NEJM, PMID 37366315), and that's a percentage rather than a fixed pound range, measured over 48 weeks instead of 24.
No head-to-head trial compares this stack to solo tirzepatide, so any "beats solo by X%" claim is anecdotal. For reference only, in separate trials tirzepatide 15 mg gave 20.9% at 72 weeks (Jastreboff 2022, NEJM, PMID 35658024) and retatrutide 12 mg gave 24.2% at 48 weeks (Jastreboff 2023, NEJM, PMID 37366315).
This is not medical advice. Consult a healthcare professional before using any peptides. These protocols are for informational purposes based on user reports and research data. Individual results vary, and peptides carry risks including gastrointestinal issues, hormonal changes, and unknown long-term effects.
References
- Jastreboff AM, Kaplan LM, Frías JP, et al. "Triple-Hormone-Receptor Agonist Retatrutide for Obesity — A Phase 2 Trial." N Engl J Med, 2023. PubMed
- Jastreboff AM, Aronne LJ, Ahmad NN, et al. "Tirzepatide Once Weekly for the Treatment of Obesity (SURMOUNT-1)." N Engl J Med, 2022. PubMed
- Coskun T, Urva S, Roell WC, et al. "LY3437943, a novel triple glucagon, GIP, and GLP-1 receptor agonist for glycemic control and weight loss: From discovery to clinical proof of concept." Cell Metab, 2022. PubMed
- Mounjaro (tirzepatide) US Prescribing Information, FDA — Dosage & Administration §2.1. FDA Label
- Retatrutide Phase 3 program (TRIUMPH-1), ClinicalTrials.gov NCT05929066. ClinicalTrials.gov