Reconstitution math without the guesswork

Reconstitution looks like arithmetic, and it is — but the failure mode is unit confusion, not math. A microgram is one-thousandth of a milligram, a U-100 unit is 0.01 mL, and the difference between getting one of those wrong and getting it right is a factor of ten. This is the entire content of "reconstitution math" — keep the units explicit, do the conversions on paper, and verify before you draw.

The three numbers you start with

Every reconstitution reduces to three inputs:

1. Peptide mass in the vial, in mg. Read it off the COA, not the marketing page.
2. Diluent volume, in mL. The amount of BAC water you intend to add.
3. Target dose, in mcg or mg. The mass per administration you need to land at.

Three numbers, two derived values. The first is concentration:

The second is the volume per dose:

That's it. The trap is that target dose is usually written in mcg and the concentration is usually expressed in mg/mL. You cannot divide one by the other without converting first. Pick one unit and stay there.

A worked example

A 5 mg vial of lyophilized peptide. You add 2 mL of BAC water. Concentration is 5 ÷ 2 = 2.5 mg/mL, or 2,500 mcg/mL. Your target dose is 250 mcg.

In mg-units: 0.25 mg ÷ 2.5 mg/mL = 0.1 mL.

In mcg-units: 250 mcg ÷ 2,500 mcg/mL = 0.1 mL.

Both arrive at 0.1 mL because the units are now consistent. On a U-100 syringe, 0.1 mL = 10 units. On a U-40 syringe, 0.1 mL = 4 units. The same volume, two different markings. This is where most errors happen — researchers drawing on a syringe whose calibration they assumed instead of confirmed.

The mcg-vs-mg failure mode

If a paper reports a dose of "300 mcg" and you write "300 mg" on your worksheet, you will draw a thousand times the intended mass. There is no clever fix for this except writing the unit next to every number, every time. Reconstitution worksheets that include a unit column have lower error rates than worksheets that assume the unit is implied.

The same logic applies to vial labels. A vial labelled "5000 mcg" is the same as "5 mg". A vial labelled "10 mg" is not the same as "10,000 mcg" if the label turns out to be 10 mcg with a misprint — always cross-reference vial mass with the COA before reconstituting.

Concentration choices have consequences

You can dissolve a 5 mg vial in 1 mL, 2 mL, 3 mL, or 5 mL of BAC water. The peptide content is identical. What changes:

• Higher concentration (e.g. 5 mg/mL): smaller volume per dose, finer-grained unit reads, more sensitivity to syringe-volume errors.
• Lower concentration (e.g. 1 mg/mL): larger volume per dose, more forgiving on the syringe, but more diluent to handle and slightly faster degradation per the peptide bond hydrolysis kinetics in solution.

The practical compromise for most lyophilized research peptides is 2.5 mg/mL — high enough to keep volumes small, low enough to read 1-unit increments without straining.

Verification before you draw

Three checks that catch the common errors:

1. Round-trip the unit math. Compute volume per dose in mg-units and again in mcg-units. They must agree.
2. Sanity-check the volume. A volume per dose under 0.02 mL on a U-100 syringe is two units — at that scale, a one-unit overdraw is a 50% error. Reconstitute at a lower concentration if the math lands there.
3. Confirm the syringe calibration. U-100 and U-40 markings look identical at a glance. Read the label, not the silhouette.

What the calculator does for you

The calculator on this site takes peptide mass, diluent volume, target dose, and syringe type as inputs and returns the four derived values: concentration in mg/mL, volume per dose in mL, syringe units to draw, and total doses per vial. It assumes nothing about the diluent beyond volume. Override the syringe type if you are working in a U-40 context. Verify against your own pen-and-paper math before relying on the output for a study log — this is a research tool, not a regulatory device.

The math is small. The unit discipline is everything.