Definitions

Glossary

Every term this site uses, defined in one or two plain sentences. If a page ever loses you, this is the place to come back to.

Lyophilized BAC water Reconstitution Concentration mcg vs mg IU vs unit vs mL U-100 syringe Dead space

Lyophilized: Freeze-dried. The peptide has been frozen and then had its water removed under vacuum, leaving a dry, stable powder. Lyophilized peptides keep for a long time; they only become fragile once mixed with liquid.
Bacteriostatic water (BAC water): Sterile water with about 0.9% benzyl alcohol added. The benzyl alcohol stops bacteria from multiplying, which is what lets a mixed vial last for weeks. It is the standard liquid for reconstituting peptides — not tap, distilled, or saline.
Reconstitution: The act of turning the dry, lyophilized powder back into a liquid by adding a measured amount of bacteriostatic water. After reconstitution the peptide can be drawn into a syringe and measured into doses.
Concentration: How much peptide is packed into each millilitre of liquid, written as mg/mL (or mcg/mL). It equals the vial's strength divided by the water you added. A 5 mg vial in 2 mL of water gives 2.5 mg/mL. Higher concentration means each dose is a smaller volume.
mcg vs mg: Both are units of weight. A milligram (mg) is one-thousandth of a gram. A microgram (mcg or µg) is one-thousandth of a milligram. So 1 mg = 1000 mcg. Vial strengths are usually written in mg; doses are usually written in mcg. Mixing the two up is the most common calculation error.
IU vs unit vs mL: These get confused because "unit" is used two ways.

mL (millilitre) is a measure of volume — actual liquid.

Unit, on an insulin syringe, is just a mark on the barrel. On a U-100 syringe, 100 units = 1 mL, so 1 unit = 0.01 mL. It measures volume, not dose.

IU (International Unit) measures biological activity, not weight or volume. Some substances are dosed in IU. Peptides here are dosed by weight (mcg), so IU generally doesn't apply — don't treat "unit" on your syringe as an "IU".
U-100 syringe: The standard insulin syringe. Its barrel is marked so that 100 units equals 1 mL of liquid — each unit is 0.01 mL. U-50 and U-40 syringes exist too, marked at 50 and 40 units per mL. The calculator converts your dose into the right unit line for whichever type you choose.
Dead space: The small amount of liquid left in the needle and syringe tip after you push the plunger all the way down. It's why a vial sometimes yields slightly fewer full doses than the math predicts. Low-dead-space syringes reduce this waste.

These definitions are educational and for laboratory research use only. They are not medical advice.