The retatrutide + cagrilintide stack (blend overview) is sourced two different ways: pre-mixed in a single vial at a fixed 5:1 retatrutide:cagrilintide ratio, or as separate component vials that can be titrated independently. Each format has tradeoffs that map onto where the user is in the staged titration protocol.
Research-context information only. Retatrutide and cagrilintide are both investigational drugs not approved by the FDA. The combination has not been formally tested in any published clinical trial. Vendor data, prices, and formats reported below come from public vendor product pages. This article reports what has been documented, not what should be done. Possession or use of investigational drugs outside an authorized clinical trial may be illegal in your jurisdiction. Consult a licensed physician for personal medical decisions.
This guide is the framework for sourcing the stack: the formats available, what each costs, what a defensible COA looks like for a two-compound blend, and the format that fits each phase of the titration.
This is not a ranked vendor list — for that, see Best Retatrutide+Cagrilintide Vendors. This guide teaches you how to evaluate any vendor yourself.
Format Options
Three formats dominate the retatrutide+cagrilintide research-vendor market.
Format 1 — Separate Vials
Standard research-vendor retatrutide vials (5 mg or 10 mg) plus standard cagrilintide vials (5 mg). Each is reconstituted separately with bacteriostatic water. Doses can be titrated independently — which matters during the staged community titration where retatrutide is ramped first, then cagrilintide is layered on a separate 4-week-per-step ramp.
Pros: independent dose control, lower per-mg cost, easier COA verification (single compound per vial). Cons: two reconstitutions, two storage timelines, two injections per week (most community sources describe same-day separate-site injection).
Format 2 — Pre-Mixed 12.5 / 2.5 mg Vial (5:1)
A single vial containing 12.5 mg retatrutide and 2.5 mg cagrilintide co-lyophilized. Reconstituted as one. Each draw delivers the fixed 5:1 ratio.
Pros: single reconstitution, single weekly injection, simpler logistics at maintenance. Cons: locked ratio means the user cannot titrate components independently; COA must address both compounds + ratio.
Format 3 — Pre-Mixed 20 / 4 mg Vial (5:1)
Same 5:1 ratio, larger total mass. Lasts longer between reconstitutions for users on extended protocols.
Pros: fewer reconstitution events; lower per-mg pricing on most vendor pages compared with the 12.5/2.5 vial. Cons: more compound mass in one vial means a single contamination event affects more weeks of dosing; same locked-ratio limitation.
Pricing Framework
Common per-compound separate-vial sizes (current prices render in the live offers below — hand-typed ranges go stale on every reprice):
| Compound | Vial size |
|---|---|
| Retatrutide | 5 mg |
| Retatrutide | 10 mg |
| Cagrilintide | 5 mg |
Pre-mixed blend pricing:
| Configuration | Total peptide |
|---|---|
| 12.5 mg reta + 2.5 mg cagri | 15 mg |
| 20 mg reta + 4 mg cagri | 24 mg |
Pattern: current vendor listings show no consistent per-mg premium for pre-mixed blends over separate-vial sourcing — depending on vendor and vial size, a pre-mixed vial can cost less or more per total mg than buying each compound separately. The tradeoff is structural rather than price: pre-mixed vials offer convenience and a fixed ratio, while during titration the locked ratio is a limitation.
Cost Per Month at Community Maintenance
Community-reported stack protocols using a 5:1 pre-mixed vial describe maintenance at 4 mg/week retatrutide + 0.8 mg/week cagrilintide, the same example the stack dosing guide uses for its vial-duration math. Applied to each sourcing path:
| Sourcing path | Per-week peptide cost | Per-month |
|---|---|---|
| Separate vials (10 mg reta + 5 mg cagri) | (4 ÷ 10 × reta vial price) + (0.8 ÷ 5 × cagri vial price) | Weekly cost × ~4.3 |
| Pre-mixed 12.5/2.5 mg vial | Vial price ÷ weeks per vial (5:1 locked; ~3 weeks at 4 mg reta / 0.8 mg cagri per week) | Weekly cost × ~4.3 |
| Pre-mixed 20/4 mg vial | Vial price ÷ weeks per vial (5:1 locked; ~5 weeks at 4 mg reta / 0.8 mg cagri per week) | Weekly cost × ~4.3 |
(Rates depend on vendor pricing at the time of purchase. Always verify the current rate on the vendor's product page.)
Which path costs less depends on the live per-mg prices at the time of purchase. The 5:1 vial only fits maintenance protocols where the cagrilintide dose is one-fifth of the retatrutide dose; community-reported protocols that pair retatrutide with a higher cagrilintide dose are described with separate vials.
How to Verify Quality on a Two-Compound Blend
A pre-mixed blend's COA needs to address two molecules and one ratio. That is more demanding than a single-compound COA, and it's where most blend-vendor COAs fall short.
What a Pre-Mixed Reta+Cagri COA Should Include
Identity confirmation (both compounds)
- Mass spectrometry showing two distinct peaks at the expected molecular weights:
- Retatrutide: ~4731 Da
- Cagrilintide: ~3775 Da
- HPLC chromatogram showing two well-resolved peaks at the expected retention times
Purity testing (both compounds)
- HPLC purity for retatrutide: 97%+ (research-grade floor)
- HPLC purity for cagrilintide: 97%+ (research-grade floor)
- Each compound assessed independently — not a single combined purity number
Ratio quantification
- Reported as the actual mass ratio in the vial (e.g., "12.4 mg retatrutide : 2.6 mg cagrilintide" or "83% retatrutide / 17% cagrilintide by mass")
- Match to the labeled ratio (5:1 = 83.3% / 16.7%)
Contamination testing
- Bacterial endotoxin
- Heavy metals
- Residual solvents
Red Flags Specific to Pre-Mixed Blends
- COA reports a single purity number without breaking it down per compound. Walk away — this means the lab didn't separate the compounds.
- No ratio quantification. Walk away — the only way to verify a 5:1 vial actually contains 5:1 is the ratio measurement.
- Mass spectrometry shows extra peaks beyond retatrutide and cagrilintide. This indicates contamination or substitution.
- HPLC retention times don't match the expected retatrutide and cagrilintide values. Identity confirmation has failed.
- Generic "blend purity 98%" without per-compound breakdown — this is not a research-grade COA.
For COA verification on the parent compounds individually, see Where to Buy Retatrutide.
