Peptide cheat sheet
The reconstitution arithmetic on one page — concentrations, syringe units and unit conversions. Built to be printed and taped inside a cupboard door.
1. Concentration — every common vial and water combination
Concentration is the only number you need to remember after mixing. Everything else is derived from it. Read down to your vial size, across to the water you added.
| Vial | + 1 ml | + 1.5 ml | + 2 ml | + 3 ml | + 5 ml |
|---|---|---|---|---|---|
| 2 mg | 2 | 1.33 | 1 | 0.67 | 0.4 |
| 5 mg | 5 | 3.33 | 2.5 | 1.67 | 1 |
| 10 mg | 10 | 6.67 | 5 | 3.33 | 2 |
| 15 mg | 15 | 10 | 7.5 | 5 | 3 |
| 20 mg | 20 | 13.33 | 10 | 6.67 | 4 |
| 30 mg | 30 | 20 | 15 | 10 | 6 |
All values in mg/ml.
2. Units to draw, by concentration and dose
Units on a U-100 insulin syringe, where 100 units is 1 ml. Find your concentration from the table above, then read across to your dose. A dash means the dose exceeds a 100-unit barrel at that concentration — add more water rather than injecting twice.
| Dose | 2 mg/ml | 5 mg/ml | 10 mg/ml | 20 mg/ml |
|---|---|---|---|---|
| 100 mcg | 5u | 2u | 1u | 0.5u |
| 250 mcg | 12.5u | 5u | 2.5u | 1.3u |
| 500 mcg | 25u | 10u | 5u | 2.5u |
| 1 mg | 50u | 20u | 10u | 5u |
| 2.5 mg | — | 50u | 25u | 12.5u |
| 5 mg | — | 100u | 50u | 25u |
| 10 mg | — | — | 100u | 50u |
3. Conversions worth knowing by heart
| 1 mg | = 1,000 mcg | the mix-up behind almost every 1,000× error |
| 1 ml | = 100 units | on a U-100 syringe — the standard |
| 1 ml | = 40 units | on a U-40 syringe — veterinary, check the barrel |
| 1 unit | = 0.01 ml | U-100 |
| 0.3 ml barrel | = 30 units | finest markings, best for small doses |
| 0.5 ml barrel | = 50 units | the common choice |
| 1 ml barrel | = 100 units | largest volume per draw |
4. The four mistakes this sheet exists to prevent
mg where you meant mcg. One milligram is a thousand micrograms. If a result looks a thousand times off, this is why.
Borrowing someone else’s unit count. Units measure volume, not mass. “I draw to 20” is meaningless without that person’s vial size and water volume. Two people with identical vials can both be right drawing 20 and 40.
Assuming every syringe is U-100. U-40 exists and uses the same unit numbers for two and a half times the volume.
An unlabelled vial. Write the concentration in mg/ml on it when you mix — not the vial size, not the water volume, the concentration. That is the number every row above depends on.
5. One worked example, start to finish
Every number on this page comes from the same two divisions. Once you have followed them once, the tables are only a shortcut.
You have a 10 mg vial and you add 2 ml of bacteriostatic water. Concentration is the peptide divided by the liquid: 10 ÷ 2 = 5 mg/ml. That is the number to write on the vial.
You want 250 mcg. First put it in the same unit as the concentration: 250 mcg is 0.25 mg. Volume is the dose divided by the concentration: 0.25 ÷ 5 = 0.05 ml.
Syringes are not marked in millilitres, so the last step converts: on a U-100 syringe 1 ml is 100 units, so 0.05 ml × 100 = 5 units. That is the mark you draw to. Doses per vial is the vial divided by the dose: 10 ÷ 0.25 = 40 doses.
Now change one thing. Add 4 ml instead of 2 and the concentration halves to 2.5 mg/ml, so the same 250 mcg becomes 0.1 ml — 10 units. Identical dose, twice the number on the barrel, and far easier to read accurately. That trade is the only real decision you make when reconstituting.
6. What to write on the vial
Three things, in this order of importance: the concentration in mg/ml, the date you mixed it, and the compound. Concentration comes first because it is the only figure the syringe maths depends on — a vial labelled “10 mg” tells you nothing useful three weeks later, since it does not say what you diluted it with.
The date matters for a reason worth separating out: the reconstituted solution and the bacteriostatic water have different shelf lives, and people routinely conflate them. The bac water shelf-life page covers which clock is which.
Print it
This page is laid out to print cleanly on one or two sheets of A4 or Letter — the tables keep their borders and the navigation drops away. Use your browser’s print command, or run your own numbers in the calculator if your vial is not on the table.