Peptide Blend Calculator

One draw, two doses, and a ratio you cannot change

A blended vial holds two or more lyophilised peptides that were reconstituted together. Everything a single-compound vial does, it still does: each component has its own concentration, which is its own mass divided by the diluent volume, and each therefore has its own micrograms per mark. Nothing about that arithmetic is new, and if that is all you needed, the single-compound reconstitution calculator already answers it.

What is new is that there is only one plunger. A syringe measures volume and nothing else, so one draw delivers every component at once. A vial mixed with 5 mg of one peptide and 10 mg of another in 2 mL carries 25 mcg of the first and 50 mcg of the second on every single mark, permanently paired. Pull to 10 marks and you have taken 250 mcg of the first and 500 mcg of the second. There is no setting that gives you one without the other.

So a blend removes a degree of freedom, and that is the honest way to describe it. Two separate vials let you set two amounts independently. One vial lets you set one number — the mark — and the second amount follows from the mass ratio you mixed at. Anchoring on either component determines the other completely, which is why the second table below has no adjustable column: there is nothing to adjust.

The lever people reach for is the diluent, and it does not work. More water makes every mark smaller in micrograms, so the mark count for any target goes up — the same 250 mcg target that is 10 marks at 2 mL becomes 25 marks at 5 mL. But the companion figure does not move at all: 500 mcg at 2 mL, 500 mcg at 5 mL. The diluent cancels out of that expression exactly, which the third table shows column by column. If you want 250 mcg of one and 300 mcg of the other, no reconstitution volume will get you there — this vial gives you 500 mcg of the second and always will. The fix is a different vial, or two vials.

A blend is also harder to be sure about than a single compound, and that is worth saying plainly. Every number on this page assumes the masses printed on the vial are the masses in it. For an unapproved compounded preparation that is an assumption, not a fact. FDA’s own assessment of several of these substances names "complexities with regard to peptide-related impurities and active pharmaceutical ingredient (API) characterization" as a reason they were placed in category 2 of its compounding bulks review — the list of bulk drug substances that in its assessment may present significant safety risks. Two compounds in one vial means two characterisations to get right and one solution in which they can interact. The diluent’s own label raises the point: Bacteriostatic Water for Injection warns that "Some drugs for injection may be incompatible in a given vehicle, or when combined in the same vehicle or in a vehicle containing benzyl alcohol. Consult with pharmacist, if available."

And the thing this page will not do at all: it names no dose. Not for either component, not for any compound, not a frequency and not a cycle. Compounded drugs are not FDA-approved, which as FDA puts it means that "FDA does not verify the safety, effectiveness or quality of compounded drugs before they are marketed", and for the peptides usually sold as blends there is no approved label and no dose-ranging trial to quote instead. The targets in the tables below are index values — the numbers you type in — not amounts anyone here is suggesting. If you do not already have a figure from someone who can see your history, this tool cannot supply one.

What one draw delivers of each — blend chart

Marks down the side, blend composition across the top, all at 2 mL of diluent. Each cell is micrograms of the first component over micrograms of the second, from a single draw.

The two numbers in a cell always move together, and their proportion is the column heading. That is the difference between a blend and two vials: here the mark is the only input, and it sets both amounts at once. The draw count is a property of the volume rather than of either peptide — at 2 mL, every component is exhausted on the same draw, always. Every figure is computed by the same functions the calculator above calls.

Anchor on one component and the other is decided

A target for the first component down the side, the blend across the top, at 2 mL of diluent. The upper figure is the mark to draw to; the lower is how much of the second component comes with it.

There is no column in this table you can adjust, which is the finding. Read across a row: the same target for the first component produces a different amount of the second in every blend, and the only thing that decided it was the mass ratio at the top. Where a cell carries a second figure for A, the target did not land on a reachable quarter-mark and that is what the barrel actually delivers. Note also what is NOT here: a diluent column. Changing the water changes the mark count in the upper line and leaves the lower line exactly where it is — see the next table.

What the diluent changes, and what it does not

The same vial — 5 mg + 10 mg, a 1 : 2 blend — reconstituted five different ways, all anchored on 250 mcg of the first component. Read down each column and notice which ones move.

Columns one, two, three and six move. Columns four and five do not — and column four is the one people expect to. The amount of the second component you receive is the target multiplied by the second mass and divided by the first, an expression the diluent volume cancels out of entirely; small wobbles would only ever be quarter-mark rounding. So "add more bacteriostatic water" makes a mark bigger and easier to read, and makes no difference whatsoever to the proportion of the two peptides you are taking. The ratio column is the vial, not the water.

Two targets one vial cannot both hit

A pair of amounts wanted from a single draw down the side, the blend across the top. Each cell anchors on the first target and reports what the second component actually delivers against what was wanted.

A cell reads "on target" only where the blend’s mass ratio already equals the ratio of the two amounts wanted — the row header names the ratio that would be needed. Everywhere else the second component is over or under, and the shortfall is not fixable: it does not depend on the diluent, on the barrel, or on how carefully the draw is made. It is the vial. If the two amounts you want are not in the proportion the vial was mixed at, the options are a differently mixed vial or two separate vials, and this page is not going to pretend otherwise.

Frequently asked questions

How do I calculate the dose of each peptide in a blend?

Treat each component separately for the concentration and together for the draw. Divide each component’s mass in mg by the diluent volume in mL to get its own mg/mL, multiply by 1000 and divide by 100 to get its micrograms per mark on a U-100 barrel. Then the mark count is the same for both, because there is only one plunger. A vial with 5 mg of one peptide and 10 mg of another in 2 mL is 25 mcg and 50 mcg a mark respectively, so 10 marks delivers 250 mcg of the first and 500 mcg of the second — always in that proportion, every draw.

Can I adjust one peptide in a blend without changing the other?

No, and this is the defining limitation of a blended vial. A syringe measures volume, both peptides are dissolved in the same volume, so any change to the draw changes both by the same factor. Drawing 20% more gives you 20% more of each. The ratio was fixed when the powders went into one vial and cannot be altered afterwards by anything you do at the syringe. If you need the two amounts to move independently, they have to be in separate vials.

Does adding more bacteriostatic water change the ratio in a blend?

No. It changes how big each mark is and nothing else. Take 5 mg plus 10 mg in 2 mL: that is 25 and 50 mcg a mark, and a 250 mcg target for the first component is 10 marks, delivering 500 mcg of the second. Mix the same masses in 5 mL and it is 10 and 20 mcg a mark, so the same target is 25 marks — but the second component still delivers 500 mcg. The diluent cancels out of that calculation exactly. More water buys a bigger, easier-to-read mark; it does not change the proportion of what you are taking.

How much of each peptide should I put in the blend?

This page will not answer that, and the reason is that there is no sourceable answer. A blend ratio is a dosing decision twice over — it fixes both amounts at once — and for the compounds usually sold this way there is no approved label and no dose-ranging trial to quote. FDA placed several of them, including BPC-157, ipamorelin acetate and kisspeptin-10, in category 2 of its compounding bulks review and wrote of BPC-157 that it "lacks sufficient information to know whether the drug would cause harm when administered to humans". A ratio invented to fill that gap would look exactly like one somebody had studied. This tool converts the numbers you were given; it does not generate them.

Which peptide in a blend runs out first?

Neither — they are exhausted on the same draw, always. That surprises people, but it follows from sharing a volume: a 2 mL vial drawn 0.1 mL at a time gives 20 draws, and every one of those draws takes the same proportion of both peptides. What differs is how many doses of each you would have got from separate vials. A 5 mg component at 250 mcg a draw is 20 doses; a 10 mg component at 250 mcg a draw would have been 40. In the blend you get 20 of each and the second component is delivered at 500 mcg a draw, not 250.

Is a blended peptide vial FDA-approved?

No. Blends are compounded preparations, and as FDA states, "Compounded drugs are not FDA-approved. This means that FDA does not verify the safety, effectiveness or quality of compounded drugs before they are marketed." Several of the individual substances are further on FDA’s category 2 list of bulk drug substances that may present significant safety risks, where the agency cites "complexities with regard to peptide-related impurities and active pharmaceutical ingredient (API) characterization". That matters more for a blend than a single vial, because the arithmetic on this page assumes both printed masses are correct and there are now two of them to be wrong.

Can two peptides be safely mixed in the same vial?

Not a question arithmetic can answer, and not one this page will guess at. The diluent’s own FDA label raises it directly: Bacteriostatic Water for Injection states that "Some drugs for injection may be incompatible in a given vehicle, or when combined in the same vehicle or in a vehicle containing benzyl alcohol. Consult with pharmacist, if available." Chemical compatibility, stability of the mixture and its shelf life are properties of the specific compounds, and for unapproved peptides nobody has established them. The label also says to "Do not store reconstituted solutions of drugs for injection unless otherwise directed by the manufacturer of the solute" — and with no manufacturer instruction there is no figure to follow.

What if my target does not land on a syringe mark?

Then it lands on the nearest quarter-mark and both components shift together. A vial with 15 mg of one peptide in 2 mL is 75 mcg a mark, so a 250 mcg target is 3.33 marks in theory and 3.25 in practice — 243.75 mcg, about 2.5% short — and the companion component is 2.5% short too, by the same proportion. A quarter mark is not a printed line on any barrel we could find a specification for; it is the finest split anyone can judge by eye between two lines. Reconstituting to a volume that puts your target on a whole mark is the fix, and it costs nothing, because the diluent does not affect the ratio.

Is a blend better than two separate vials?

It is fewer injections and fewer vials, and it is one fewer thing you can set. Two vials give two independent amounts and two independent decisions about when to change one of them; a blend gives one draw and a proportion decided at mixing. The arithmetic says nothing about whether that trade is worth making for any particular pair of compounds — that depends on what is in them and why, which is a clinical question and not a calculation. What the arithmetic does say is that the trade is real and is not recoverable at the syringe.

Sources

1. [1]FDA label — Bacteriostatic Water for Injection, USP, Hospira Inc. (DailyMed SPL 87d6e9dc-fe3b-4593-ac9a-d7493d1959c7). The diluent, and the only primary source here that addresses combining drugs in one vehicle: "Some drugs for injection may be incompatible in a given vehicle, or when combined in the same vehicle or in a vehicle containing benzyl alcohol. Consult with pharmacist, if available." and "Do not store reconstituted solutions of drugs for injection unless otherwise directed by the manufacturer of the solute."
2. [2]U.S. Food and Drug Administration — Category 2 of the Bulk Substances Nominated Under Sections 503A or 503B of the Federal Food, Drug, and Cosmetic Act. On BPC-157: "Compounded drugs containing BPC-157 may pose risk for immunogenicity for certain routes of administration and may have complexities with regard to peptide-related impurities and active pharmaceutical ingredient (API) characterization. FDA has identified no, or only limited, safety-related information for the proposed routes of administration. Therefore, the agency lacks sufficient information to know whether the drug would cause harm when administered to humans."
3. [3]U.S. Food and Drug Administration — Compounding and the FDA: Questions and Answers. "Compounded drugs are not FDA-approved. This means that FDA does not verify the safety, effectiveness or quality of compounded drugs before they are marketed."
4. [4]embecta (formerly BD Diabetes Care) — Ultra-Fine insulin syringes. Barrel capacities, and the only sub-unit graduation any manufacturer states: "Designed with large dose unit markings, with ½ unit scale marking available on the 0.3mL barrel." and "availability in 1 mL, 0.5 mL, and 0.3 mL capacities, with 6 mm, 8 mm and 12.7 mm needles."