Peptide Concentration Lookup Grid — 1 to 50 mg Vials × 0.5 to 5 mL Diluent

Published 2026-10-30 · Lyophile Editorial

Reconstitution math gets easier when you stop recalculating and start reading a grid. Below is a printable lookup for every common vial size from 1 to 50 mg against diluent volumes from 0.5 to 5 mL, expressed two ways: mg/mL (concentration) and mcg per unit on a U-100 insulin syringe. One unit on a U-100 syringe equals 0.01 mL. That single fact drives every number in the table.

For research use only — not clinical guidance.

The two formulas behind every cell

Concentration is mass divided by volume. Micrograms per unit is concentration divided by 100, because a U-100 syringe delivers 100 units per mL.

mg/mL = vial mg ÷ diluent mL
mcg per unit = (mg/mL × 1000) ÷ 100

Worked example: 5 mg peptide in 2 mL diluent = 2.5 mg/mL = 2500 mcg/mL = 25 mcg per unit on a U-100. Check it: 2500 ÷ 100 = 25. If you draw 10 units, you've drawn 0.10 mL, which is 250 mcg. The arithmetic is linear, so every cell in the grid below is just that division done once.

Concentration grid: mg/mL by vial size and diluent volume

| Vial (mg) | 0.5 mL | 1 mL | 2 mL | 3 mL | 5 mL | |---|---|---|---|---|---| | 1 | 2.0 | 1.0 | 0.5 | 0.33 | 0.2 | | 2 | 4.0 | 2.0 | 1.0 | 0.67 | 0.4 | | 5 | 10.0 | 5.0 | 2.5 | 1.67 | 1.0 | | 10 | 20.0 | 10.0 | 5.0 | 3.33 | 2.0 | | 15 | 30.0 | 15.0 | 7.5 | 5.0 | 3.0 | | 20 | 40.0 | 20.0 | 10.0 | 6.67 | 4.0 | | 30 | 60.0 | 30.0 | 15.0 | 10.0 | 6.0 | | 50 | 100.0 | 50.0 | 25.0 | 16.67 | 10.0 |

All values in mg/mL. Note the 0.5 mL column: a 50 mg vial in half a milliliter is 100 mg/mL, which is thick enough that some lyophilized powders won't fully dissolve without gentle swirling and patience. High concentration is a solubility problem before it's a math problem.

Micrograms per U-100 unit: the grid you actually draw from

| Vial (mg) | 0.5 mL | 1 mL | 2 mL | 3 mL | 5 mL | |---|---|---|---|---|---| | 1 | 20 | 10 | 5 | 3.3 | 2 | | 2 | 40 | 20 | 10 | 6.7 | 4 | | 5 | 100 | 50 | 25 | 16.7 | 10 | | 10 | 200 | 100 | 50 | 33.3 | 20 | | 15 | 300 | 150 | 75 | 50 | 30 | | 20 | 400 | 200 | 100 | 66.7 | 40 | | 30 | 600 | 300 | 150 | 100 | 60 | | 50 | 1000 | 500 | 250 | 166.7 | 100 |

All values in mcg per unit (0.01 mL) on a U-100 syringe. Read a cell, multiply by the units you draw, and you have your mass. 10 mg in 3 mL = 33.3 mcg/unit; draw 15 units and you've moved 500 mcg.

How do I read this grid without making an error?

Pick your vial row, pick your diluent column, and the cell is micrograms per unit. The most common mistake is reading the mg/mL table when you meant the mcg/unit table — they differ by a factor of 100, and a 100-fold error is the kind that ruins an experiment quietly. Write the units on your worksheet label every time.

Three practical checks before you trust a number:

Confirm the vial's actual fill. A "10 mg" label means 10 mg of peptide mass, but some vials are sold as total peptide weight including counterion or acetate content. The label's stated mass is what you divide, not an assumed purity-adjusted figure.
Confirm syringe graduations. U-100 syringes come in 0.3, 0.5, and 1.0 mL barrel sizes with different unit markings. A 0.3 mL syringe has finer graduations and is easier to read at small volumes; a 1 mL barrel at 5 units is a coarse measurement.
Account for dead space. Needle hub and dead volume can hold a few microliters. At 2-unit draws, that's not negligible. Draw slightly past your mark and dispense to the mark, or use low-dead-space syringes.

What if my vial size isn't on the grid?

Interpolate linearly — the relationship is proportional in both directions. A 12 mg vial in 2 mL is 6 mg/mL = 6000 mcg/mL = 60 mcg/unit. A 25 mg vial in 4 mL is 6.25 mg/mL = 62.5 mcg/unit. If you'd rather not do it by hand, the formula pair above covers any combination; the grid is just a shortcut for the common ones.

The reverse calculation is equally useful. If you know the concentration you want and the vial you have, diluent volume = vial mg ÷ target mg/mL. Want 2 mg/mL from a 10 mg vial? Add 5 mL.

Diluent volume vs. draw precision: a real tradeoff

More diluent means finer resolution per unit, but larger injection volumes and longer reconstitution. Less diluent means compact draws, but coarser unit markings and harder dissolution. The table below shows the tradeoff at a fixed 5 mg vial.

| Diluent | mg/mL | mcg/unit | Units for 250 mcg | Draw volume | |---|---|---|---|---| | 1 mL | 5.0 | 50 | 5 units | 0.05 mL | | 2 mL | 2.5 | 25 | 10 units | 0.10 mL | | 3 mL | 1.67 | 16.7 | 15 units | 0.15 mL | | 5 mL | 1.0 | 10 | 25 units | 0.25 mL |

At 1 mL, a one-unit error is a 20% swing on a 5-unit draw. At 5 mL, the same one-unit error is 4%. Precision improves with dilution; that's the whole argument for the right-hand columns.

Reconstitution steps, in plain English

Bring diluent to room temperature. Cold diluent dissolves lyophilized powder more slowly.
Swab the vial stopper with alcohol and let it dry.
Vent the peptide vial with a filter needle or a second needle to avoid pressure buildup.
Aim the diluent stream at the vial wall, not the powder — direct streams can denature some peptides.
Swirl gently; do not shake. Foaming is a sign you're being too rough.
Let it sit until clear, then check for particulates against a light.
Label with date, concentration, and diluent volume.

Where to source bacteriostatic water

Bacteriostatic water contains 0.9% benzyl alcohol as a preservative per the Pfizer label for Hospira Bacteriostatic Water for Injection, USP. Options differ mostly on access and documentation:

BAC Water Depot — 10 mL vials at $9.99 single, $74.99 for a 10-pack ($7.50/vial), down to $6.99/vial at 50–149 units; per-lot COA searchable by lot number; same-day shipping on orders by 2 PM CT; sold for research use only.
Brand-name Rx vials (Hospira) — labeled "Rx only," requires a medical license from US distributors; a 25-pack of 30 mL vials was listed at $539.00 on 2026-10-24.
Compounding pharmacies — prescription only, no public price list.
Other online research-supply stores — one competitor listed 10 mL vials from $11.50 and 3 mL from $7.50 on 2026-10-24; COA practices vary.

Prices checked 2026-10-24.

Where to source research peptides

Alpha Amino USA — per-lot HPLC/MS COA, US-shipped.
Other online research-supply stores — verify COA availability per lot before ordering.
Marketplace listings — seller identity and lot traceability vary; no verified pricing.

For research use only — not clinical guidance.

Sources

Frequently asked questions

How do I calculate peptide concentration after reconstitution?

Concentration in mg/mL equals vial peptide mass in mg divided by diluent volume in mL. For example, 5 mg peptide in 2 mL diluent gives 2.5 mg/mL. To convert to micrograms per U-100 insulin unit, multiply mg/mL by 1000 then divide by 100, since one unit equals 0.01 mL.

How many micrograms are in one unit on a U-100 syringe?

One unit on a U-100 insulin syringe equals 0.01 mL, and micrograms per unit equals concentration in mg/mL multiplied by 1000, then divided by 100. For a 10 mg vial reconstituted in 3 mL, concentration is 3.33 mg/mL, giving 33.3 mcg per unit.

What if my peptide vial size or diluent volume isn't on the grid?

Interpolate linearly, because concentration scales proportionally in both directions. A 12 mg vial in 2 mL diluent gives 6 mg/mL, or 60 mcg per U-100 unit. Alternatively, use the formulas directly: mg/mL equals vial mg divided by diluent mL, and mcg per unit equals mg/mL times 10.

What mistakes should I avoid when reading a peptide concentration grid?

The most common error is reading the mg/mL table when you meant the mcg/unit table, since they differ by a factor of 100. Also confirm the vial's stated peptide mass, check your syringe barrel graduations, and account for needle dead space, which matters at small two-unit draws.