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The three strengths hold the same lyophilized retatrutide and differ only in how much of it is sealed in the vial. That choice matters for two practical reasons. The first is concentration: the volume of diluent a vial can reasonably take is fixed by the vial, so the labeled mass sets the range of concentrations available to you. Two millilitres of bacteriostatic water in a 10 mg vial gives a nominal 5 mg/mL; the same two millilitres in a 20 mg vial gives 10 mg/mL.

The second is cost per milligram, shown on every card above. The 20 mg vial carries the lowest per-mg price, which is what matters when a protocol will consume material over weeks. Against that, retatrutide in solution has a far shorter usable life than the dry cake, so the largest vial is not automatically the most economical choice for short or low-concentration work.

A COA is a laboratory's signed report on one specific lot — never a general claim about the product line. The certificates behind these batches are issued by ILS Laboratories and cover peptide purity by RP-HPLC, identity confirmation, net peptide content in milligrams, heavy metals by ICP-MS, sterility, bacterial endotoxin per USP <85>, and a fentanyl screen.

Reading one is mostly a matter of matching things up. Confirm the lot number on the certificate is the lot printed on your vial: a certificate for a different lot tells you nothing about the vial in your hand. Note the analysis date, because purity is a measurement taken on a day, not a permanent property. Read net peptide content alongside purity rather than instead of it — purity is the fraction of the peptide present that is retatrutide, while net content is how many milligrams of peptide the vial actually holds, and a protocol needs both numbers. Then check that the contaminant panel reads not detected rather than not tested.

Vials ship sealed and cold-stored. As a dry cake retatrutide is comparatively stable and is normally kept refrigerated, protected from light, with the stopper undisturbed; freezing an unopened vial is reasonable for long-term storage, but repeated freeze-thaw cycling is not — each cycle is a stress event on the peptide.

Lyophilized peptide is hygroscopic, which is why vials are sealed under vacuum and why a vial should be allowed to reach room temperature before the stopper is ever pierced. Opening a cold vial into humid air condenses water onto the powder before you have added any diluent at all. Once the material is in solution the constraints tighten considerably: a reconstituted vial belongs in the refrigerator rather than on the bench, and should be treated as having a much shorter working life than the sealed powder it came from.

Reconstitution is the step that turns the dry cake into a solution of known concentration. In outline: the diluent is measured out — bacteriostatic water for most work, sterile water where a preservative is unwanted — both stoppers are wiped with alcohol, and the diluent is introduced slowly down the inside wall of the vial rather than jetted onto the cake, because peptides are shear-sensitive and foaming denatures material. The vial is then swirled, never shaken, until the cake has fully dissolved and the solution is clear.

Concentration is arithmetic, not judgement: labeled mass divided by the volume of diluent added, expressed in mg/mL. The reconstitution calculator does that for any vial and volume pairing, and the illustrated guide walks the sequence in order.