The Peptide Dosage Chart: Vial Size, Water Volume, Concentration, Units

Search for peptide dosage chart and most results try to answer a question they are not qualified to answer: how much of a given compound a person should use. This page does something narrower and more defensible. It is a reconstitution reference table, and it answers a purely mathematical question: if you put a known mass of lyophilized powder into a known volume of liquid, what concentration results, and how many marks on an insulin syringe correspond to a given quantity of that concentration?

That distinction matters. Concentration arithmetic is fixed by physics and does not vary with the compound, the supplier, or anyone's opinion. A 10 mg vial dissolved in 2 mL of bacteriostatic water yields 5 mg/mL whether the powder is BPC-157, TB-500, or GHK-Cu. Quantities, by contrast, are compound-specific, context-specific, and in the case of research peptides usually unestablished in humans altogether. You will not find any recommended amounts below.

Three variables define the entire problem. The first is the mass of peptide in the vial, printed on the label in milligrams, commonly 2, 5, 10, 20 or 50 mg. The second is the volume of bacteriostatic water you add, which you choose, typically between 1 and 5 mL. The third is the volume you withdraw, read off the syringe barrel in insulin units. Fix any two and the third follows. There is no hidden step, no conversion factor that depends on the peptide, and no need for the molecular weight of the compound.

The reason this trips people up is a units problem, not a math problem. Vials are labeled in milligrams, syringes are labeled in insulin units, and most discussion of quantities happens in micrograms. Three different scales, none of which convert to the others without knowing the concentration. Once you have the concentration, all three collapse into a single multiplication. The rest of this page sets out that multiplication and then tabulates it exhaustively so you never have to perform it.

Important: research peptides are classified for laboratory research use only in the United States and the European Union, and are not approved by the FDA or EMA for human use. Legal status varies by jurisdiction. Nothing here is medical advice, and the arithmetic being correct says nothing about whether any given use is safe or lawful. Consult a qualified healthcare professional, and see our medical disclaimer.

An insulin syringe is not graduated in volume. It is graduated in insulin units, which is a measure of biological activity, and the graduations only translate to volume because insulin is sold at a standardized strength. The overwhelmingly common standard is U-100, meaning 100 international units of insulin per milliliter. On a U-100 syringe, therefore, the mark labeled 100 sits exactly at 1 mL, the mark labeled 50 sits at 0.5 mL, and the mark labeled 1 sits at 0.01 mL.

This gives the single rule that produces every number in this article:

1 unit = 0.01 mL = 1/100 of a milliliter.

From there the conversion to mass is one step. If the solution holds C milligrams per milliliter, then one unit contains C × 0.01 mg. Multiply by 1,000 to convert to micrograms and the 0.01 becomes 10:

• Micrograms per unit = concentration in mg/mL × 10
• Concentration in mg/mL = vial mass in mg ÷ water volume in mL
• Units for a target amount = target in mcg ÷ micrograms per unit

Test it against a case you can verify by hand. A 5 mg vial reconstituted with 2 mL of bacteriostatic water gives 5 ÷ 2 = 2.5 mg/mL. Multiply by 10 and one unit holds 25 mcg. Sanity check the other direction: the full 2 mL is 200 units, and 200 units × 25 mcg = 5,000 mcg = 5 mg, which is exactly what the label said was in the vial. The arithmetic closes. Any chart that does not close in this way contains an error.

Notice what the rule does not require. It does not require the molecular weight of the peptide, its sequence, its purity, or its solubility. Those properties matter enormously for whether the peptide dissolves cleanly and stays intact, but they are irrelevant to the concentration calculation. Mass divided by volume is mass divided by volume. This is why one table can cover every compound at once, and why per-compound calculators differ only in the presets they load, not in the mathematics they run.

The table below is the core reference. Rows are vial sizes as they are commonly sold, columns are bacteriostatic water volumes. Each cell gives the resulting concentration in mg/mL and, beneath it, the micrograms contained in 1 unit of a U-100 insulin syringe. The second figure is simply the first multiplied by ten.

Several structural patterns are worth naming, because recognizing them lets you extrapolate to combinations not listed. First, every cell in a row contains the same total mass. Moving right along a row does not dilute the peptide out of existence, it distributes the identical quantity across a larger volume, so each unit carries proportionally less. Second, the diagonals repeat: 2 mg in 1 mL, 10 mg in 5 mL, and any other pairing with the same ratio all give 20 mcg per unit. The chart really has only one degree of freedom, the ratio mg per mL.

Third, the round numbers cluster in predictable places. Reconstituting a vial with a volume in milliliters numerically equal to one tenth of the vial mass in milligrams always yields 100 mcg per unit. Reconstituting at half that water volume doubles it to 200 mcg per unit. Practitioners who prefer arithmetic they can do without a calculator tend to gravitate toward whole-milliliter volumes for exactly this reason, and there is nothing wrong with that preference as long as the resulting numbers are checked.

Fourth, note the extremes. A 50 mg vial in 1 mL is a dense solution at 50 mg/mL, and not every peptide will dissolve fully at that concentration. Conversely a 2 mg vial in 5 mL gives 4 mcg per unit, which means small quantities require many units and the whole vial occupies 500 units, or five full syringes worth of volume. Solubility limits and total volume are practical constraints the arithmetic does not know about, which is why the chart is a starting point rather than a decision.

Volumes other than those four columns are handled by the same formula. For 2.5 mL, divide the vial mass by 2.5 then multiply by 10. A 5 mg vial in 2.5 mL is 2 mg/mL, or 20 mcg per unit. For 1.5 mL, a 10 mg vial gives 6.67 mg/mL, or 66.7 mcg per unit. Nothing special happens at non-integer volumes.

The first table runs the calculation forward, from vial and water to concentration. The table below runs it backward, which is the direction most people actually need at the moment they are holding a syringe. Pick your concentration from the left column, expressed as micrograms per unit, then read across to find how many units contain a given quantity.

Two regions of this table deserve a warning label, and both are about measurement precision rather than about any compound. Values above 100 units exceed the capacity of a standard 1 mL insulin syringe. They appear in the table because the arithmetic produces them, but in practice they mean the solution is too dilute for the quantity in question, and a smaller water volume would give a more workable number.

Values below about 2 units are difficult to measure reliably. A standard U-100 syringe is graduated in whole units, occasionally half units on smaller barrels. Reading 0.4 units means estimating a fraction of the smallest printed division, which introduces a relative error that can easily reach twenty percent or more. Studies comparing insulin delivery devices have repeatedly found that accuracy degrades sharply at very small volumes, which is a general property of graduated syringes and not specific to peptides. If the chart sends you below two units, the sensible response is to reconstitute at a lower concentration next time so the same quantity occupies a larger, more readable volume.

The comfortable middle of the table, roughly 5 to 50 units, is where a graduated syringe does its best work. That range is wide enough to accommodate almost any combination of vial size and quantity, which is precisely the freedom the water volume gives you. Choosing the reconstitution volume is, in effect, choosing where on this table you want to land.

Fractional units in the table, such as 12.5 or 6.25, are readable on syringes with half-unit graduations and are otherwise a signal to adjust the concentration. Rounding 6.25 units to 6 units is a four percent difference, which is usually within the noise of the whole process, but rounding 1.25 to 1 is a twenty percent difference, which is not.

Three worked examples show the chart in both directions. None of them recommends a quantity. Each starts from an arbitrary target chosen only to demonstrate the arithmetic.

Example 1, forward direction. You have a 10 mg vial and you add 2 mL of bacteriostatic water. Concentration is 10 ÷ 2 = 5 mg/mL. Multiply by 10 and each unit holds 50 mcg. Suppose the target quantity is 250 mcg. Divide: 250 ÷ 50 = 5 units. Closing check: the vial holds 10,000 mcg, so it contains 10,000 ÷ 250 = 40 such withdrawals, and 40 × 5 units = 200 units = 2 mL, which is the volume you added. Correct.

Example 2, backward direction. You have a 5 mg vial and you want each unit to represent a round 20 mcg, because that makes mental arithmetic trivial. Working backward, 20 mcg per unit means 2 mg/mL, and 5 mg ÷ 2 mg/mL = 2.5 mL of bacteriostatic water. Now 100 mcg is 5 units, 200 mcg is 10 units, and 500 mcg is 25 units. Designing the concentration around the arithmetic you want, rather than defaulting to a round water volume, is often the more sensible order of operations.

Example 3, a large vial. You have a 50 mg vial. At 1 mL it becomes 50 mg/mL and each unit holds 500 mcg, so a 250 mcg quantity would be half a unit, which is unreadable. At 5 mL it becomes 10 mg/mL and each unit holds 100 mcg, so 250 mcg is 2.5 units, still awkward. The whole vial at 5 mL is 500 units of volume, meaning the solution has to remain stable in the refrigerator for a long time. Large vials therefore force a genuine trade-off between readable syringe volumes and long storage of reconstituted solution, and that trade-off is exactly what the chart makes visible.

A note on stability that the arithmetic cannot capture: once a lyophilized peptide is reconstituted, it enters solution and becomes subject to hydrolysis, oxidation, aggregation and adsorption to container surfaces. The literature on protein and peptide pharmaceuticals is consistent that the dry, lyophilized state is substantially more stable than the aqueous state, which is why these compounds are freeze-dried in the first place. Choosing a very large reconstitution volume for a large vial commits you to keeping the solution for longer, and that is a stability consideration rather than a math consideration.

If you would rather not run these calculations by hand, the Peptide Lab reconstitution calculator performs all three directions and shows the intermediate concentration, so you can verify each step against the tables above.

Everything above assumes a U-100 insulin syringe, where 100 units equals 1 mL. That assumption is correct for the vast majority of syringes sold today, but it is an assumption, and it is the single most consequential one on this page. If it is wrong, every number is wrong by a fixed multiple.

U-40 syringes still exist, primarily in veterinary contexts and in some markets outside North America and Western Europe. On a U-40 syringe, 40 units equals 1 mL, so 1 unit equals 0.025 mL, two and a half times the volume of a U-100 unit. Using the tables above with a U-40 syringe would deliver 2.5 times the intended quantity. The syringe barrel is printed with its scale, usually near the plunger end, and checking it once when you open a new box is the entire mitigation.

Within the U-100 family, barrel capacity varies and this affects readability, not the conversion. Common formats are:

• 0.3 mL barrel (30 units): the finest graduations, often marked in half units. Best precision, but caps out at 30 units, so it is only usable with more concentrated solutions.
• 0.5 mL barrel (50 units): a common compromise, usually whole-unit graduations, sometimes half units.
• 1 mL barrel (100 units): maximum capacity, coarsest graduations, typically marked every 1 or 2 units.

All three read 1 unit as 0.01 mL. The difference is how easy it is to read a small number accurately, which is the practical reason a 0.3 mL barrel is preferred when the target lands in the low single digits of units. Choosing a barrel is choosing a resolution.

Two further mechanical details matter for accuracy. Dead space, the volume trapped in the needle hub after the plunger bottoms out, is minimized in fixed-needle insulin syringes but is real in detachable-needle designs, and it becomes proportionally significant at very small volumes. Air bubbles displace liquid, so a bubble occupying 2 units of a 10 unit draw represents a twenty percent shortfall. Both effects are invisible to arithmetic and both are eliminated by ordinary careful technique.

No. Bacteriostatic water is sterile water for injection containing approximately 0.9 percent benzyl alcohol as a preservative. The benzyl alcohol inhibits bacterial growth, which is what allows a multi-dose vial to be entered more than once. It contributes no peptide mass, so the concentration calculation is identical whether you reconstitute with bacteriostatic water, plain sterile water, or bacteriostatic sodium chloride. Mass in, volume in, concentration out.

What the choice of diluent changes is everything other than the arithmetic. Sterile water for injection contains no preservative and is intended for single use, since once the stopper is pierced there is nothing suppressing microbial growth in the vial. Bacteriostatic water permits repeated entry, which is the usual reason it is chosen for multi-dose reconstitution. Compounding standards for sterile preparations, such as USP General Chapter <797>, treat the presence or absence of an antimicrobial preservative as a primary determinant of permitted storage time, and that logic applies here regardless of jurisdiction.

Benzyl alcohol is not inert. It is contraindicated in neonates, where it has been associated with a serious toxicity syndrome documented in the pediatric literature since the early 1980s, and some individuals are sensitive to it. It can also interact with certain peptides, and a minority of compounds are recommended by their suppliers to be reconstituted with plain sterile water or with acetic acid solutions for solubility reasons. Supplier documentation is the authority on this, not a general chart.

Technique during reconstitution affects yield in ways the chart cannot show. Directing the stream of water down the inner wall of the vial rather than blasting it directly onto the powder cake reduces mechanical stress on the peptide. Swirling gently until dissolved, rather than shaking, avoids the foaming that indicates protein denaturation at the air-liquid interface. These are standard handling practices for peptide and protein solutions and they exist because aggregation at interfaces is a well-documented degradation pathway.

Finally, storage. Reconstituted peptide solutions are generally kept refrigerated and protected from light, and the lyophilized powder is far more stable than the solution. None of this alters mg divided by mL, but all of it determines whether the peptide you calculated is still the peptide you have. If you are new to the underlying chemistry, our primer on what peptides are covers why these molecules are so much more fragile in water than in the dry state.

The errors that appear repeatedly are all failures of unit discipline rather than failures of calculation. Each has a check that catches it in seconds.

Confusing units with milliliters. Reading a chart that says 10 and drawing to the 10 mL mark, or treating a chart value in units as though it were a volume in milliliters, produces a hundredfold error. The check: 1 mL is 100 units, and a 1 mL insulin syringe is the entire barrel. If your calculated draw is more than the full syringe, something is wrong.

Confusing milligrams with micrograms. There are 1,000 mcg in 1 mg. A target expressed as 0.25 mg and one expressed as 250 mcg are identical, but a target expressed as 250 mg is a thousand times larger than 250 mcg and, for most research peptides, physically impossible from a single vial. The check: compare the target to the total vial mass. If a single withdrawal would exhaust more than the entire vial, the units are wrong.

Assuming more water means more peptide per unit. Adding water can only reduce the mass per unit. This is intuitive when stated plainly and yet is inverted surprisingly often when someone tries to fix a draw that feels too small by adding diluent. The check: total mass is fixed by the label and cannot change.

Reusing a chart after changing the water volume. A chart computed for 2 mL is silently wrong if the vial was actually reconstituted with 3 mL. Since the vial itself carries no record of what you added, write the volume and the date on the vial label at the moment of reconstitution. This one habit prevents more errors than any calculator.

Applying a chart across different vial sizes. The same number of units means different masses in a 5 mg vial and a 10 mg vial reconstituted with the same water volume, by exactly a factor of two. When switching to a new vial size, recompute rather than reusing the unit count from memory. The closing check described earlier catches all five of these errors at once: multiply your micrograms per unit by the total units of volume you added, and confirm the product equals the labeled vial mass.

The arithmetic is exact, but it rests on assumptions that are not always true. Four of them are worth stating explicitly, because each one puts a boundary on how far the table should be trusted.

The label mass may not be the peptide mass. Many peptides are supplied as salts, most often acetate or trifluoroacetate, and the counter-ion contributes to the total powder weight. A vial labeled 10 mg may contain somewhat less than 10 mg of the peptide itself depending on how the supplier defines the mass, and net peptide content is reported on a certificate of analysis when one is provided. Reputable suppliers state whether the label refers to gross or net peptide weight. The chart assumes the label mass is the peptide mass, which is the best available assumption in the absence of a certificate of analysis but not a guaranteed one.

Vials are often overfilled. Manufacturers commonly add a small excess so that the labeled quantity can actually be withdrawn after accounting for losses. That overfill is not quantified on the label and cannot be assumed. The chart treats the label as exact.

Blends multiply the complexity. A combination product containing several peptides in one vial has a total mass on the label that is the sum of its components, and each component has its own concentration in the reconstituted solution. A blend labeled as containing 10 mg total across two peptides in equal parts, reconstituted with 2 mL, gives 5 mg/mL total but only 2.5 mg/mL of each component, or 25 mcg per unit each rather than 50. Every blend calculation requires knowing the ratio, and if the ratio is not disclosed, the per-component concentration cannot be determined at all. Our guide to combining peptides covers why component ratios are the pivotal variable in these products.

Nothing here speaks to biology. Concentration is not exposure. What happens after administration depends on route, absorption, distribution, metabolism and clearance, and peptides in circulation typically have half-lives measured in minutes to hours absent chemical modification such as PEGylation or cyclization. Two solutions of identical concentration can behave completely differently in an organism. The chart is a plumbing diagram, not a pharmacology model.

It also bears repeating that the substantial majority of research peptides have no established human dosing at all. BPC-157, to take the most-searched example, has over a hundred published preclinical studies and, as of 2026, no completed Phase III human trials registered. A precise number of syringe units is not evidence of a well-characterized quantity. Precision and validity are different things.

A single general table covers the mathematics completely, so the honest answer is that per-compound calculators exist for convenience rather than for correctness. What they add is preloaded context: the vial sizes a given compound is typically sold in, the diluent its suppliers usually specify, the concentration ranges at which it reliably dissolves, and the molecular weight for anyone who needs to convert between mass and molar units.

Klow Peptide maintains 18 compound-specific reconstitution calculators alongside the general tool, covering the peptides most often searched for, including BPC-157, TB-500, GHK-Cu and CJC-1295. All of them are reachable from the Peptide Lab, which also includes a tracker for logging reconstitution dates and volumes so the information stays attached to the vial rather than to memory. Every one of them runs the same equation set out at the top of this article. If a calculator ever disagrees with the tables here, the tables are the reference and the discrepancy is a bug worth reporting.

There is a reasonable argument for using the tables rather than a tool, at least once. Working the calculation by hand and confirming that it closes, that micrograms per unit times total units equals the vial mass, builds the intuition that catches the hundredfold errors described earlier. A calculator that silently accepts a mistyped input will happily return a confidently wrong answer. A person who knows that a 5 mg vial in 2 mL gives 25 mcg per unit will notice immediately when a screen says 250.

Independent of any tool, a few record-keeping habits carry more weight than arithmetic precision: label each vial with its reconstitution date and the exact volume added, verify the syringe scale on every new box, and keep the supplier certificate of analysis if one was issued. These practices are what make a number traceable months later.

Final reminder: this article is educational and covers unit conversion only. Research peptides are not approved by the FDA or EMA for human use, their legal status differs by country, and most of the evidence base is preclinical rather than clinical. Any decision about whether, how, or in what quantity to use any compound belongs with a qualified healthcare professional who knows your circumstances. See our full medical disclaimer and editorial policy.