Peptide blends: the math of multi-compound vials

In a blend vial, every compound is dissolved in the same water, so each has its own concentration (its mg divided by the total mL), and every unit you draw contains all of them in a fixed ratio. You can’t draw more of one without drawing more of the others, so blend math is about working out what each draw contains, not choosing amounts separately. The peptide blend calculator shows the mg of every compound in each unit you draw.

A two-compound example

The numbers here are for illustration only and are not a dose.

A vial is labeled 10 mg compound A + 10 mg compound B. You add 2 mL of water.

• A: 10 ÷ 2 = 5 mg/mL, so 0.05 mg per unit
• B: 10 ÷ 2 = 5 mg/mL, so 0.05 mg per unit
• A 10-unit draw (0.1 mL) contains 0.5 mg of A and 0.5 mg of B

The ratio in the syringe is always the ratio on the label, here 1 to 1. Add more water and both amounts per unit fall together. Add less and both rise together.

A four-compound example

Some vials list several components with a single “total” on the front. Take a vial (numbers for illustration only, not a dose) labeled 80 mg total: 50 mg + 10 mg + 10 mg + 10 mg, mixed with 2 mL:

The total row is the least useful number here. What matters is each component’s own line. The blend calculator takes each component’s mg and your water volume, and shows exactly what a given number of units contains.

The ratio problem

Because the ratio is fixed, a blend can only match a set of prescribed amounts that happen to be in the same ratio.

Say a prescriber specified 0.5 mg of A and 0.25 mg of B, but the vial is 1 to 1. A draw that gives 0.5 mg of A also gives 0.5 mg of B, twice what was intended. A draw that gives 0.25 mg of B gives only 0.25 mg of A. No amount of water fixes this. If your prescribed amounts don’t match your vial’s ratio, talk to the pharmacist before you inject.

Don’t make your own blends

Combining separate products in one vial or syringe raises questions the math can’t answer:

• Compatibility. Bacteriostatic water’s own label warns that some drugs may be incompatible “when combined in the same vehicle or in a vehicle containing benzyl alcohol”, and says to consult a pharmacist (label).
• Unknown safety. Writing about compounded semaglutide products that add vitamins or other ingredients, the FDA says “the safety and effectiveness of combining semaglutide with other ingredients has not been established” (FDA).
• No oversight. Compounded drugs are not FDA-approved, and the FDA doesn’t verify their safety, effectiveness or quality before they’re sold (FDA).
• Contamination. Every extra puncture and transfer is another chance for contamination. Use a new needle and syringe every time (CDC).

Peptinote doesn’t recommend combining compounds. We only show the math for a vial you already have.

Blend nicknames

Some blends are sold under nicknames rather than ingredient names. A nickname isn’t an ingredient list, and the contents can differ from one label to the next. Always work from the mg printed for each component on your label. If the label only shows a total, you can’t do the per-compound math; ask the pharmacy that dispensed it for the breakdown.

Common mistakes

• Treating the total mg as a single compound. “80 mg” in the calculator would be wrong for every component.
• Mixing up mg and mcg on the label. Small components are often listed in mcg (1 mg = 1,000 mcg).
• Mixing two separately reconstituted vials in one syringe.
• Assuming “10 mg” on a two-compound label means 10 mg each. It might be 5 mg + 5 mg. Read the breakdown.

Questions people ask