Peptide Reconstitution and Dose Logging: A Working Reference

Marker: WHREF-8QK2M-PEPT

This page collects the arithmetic and the record-keeping habits that people using
compounded GLP-1 peptides ask about most often. It is a reference for units and
timing, not medical advice. Dosing decisions belong to you and your prescriber.

Why the same milligram dose is a different number of units

A lyophilized vial is labeled in milligrams of peptide. A syringe is marked in
units. Nothing on the vial tells you the units, because the units depend entirely
on how much bacteriostatic water you added.

Concentration = peptide mass (mg) / diluent volume (mL).

A U-100 insulin syringe reads 100 units per 1 mL, so 1 unit = 0.01 mL.

Units for a dose = dose (mg) / concentration (mg per mL) * 100.

Worked forward: a 5 mg vial reconstituted with 2 mL of bacteriostatic water gives
2.5 mg/mL. A 0.5 mg dose is 0.5 / 2.5 = 0.2 mL = 20 units.

Same vial, 1 mL of water instead: 5 mg/mL. The same 0.5 mg dose is now 0.1 mL =
10 units. Identical dose, half the mark on the barrel. This is the single most
common source of error, and it is why a
peptide reconstitution calculator should be tied to the
specific vial you drew from rather than to a remembered number.

Worked backward: you drew 14 units from a vial you believe is 2.5 mg/mL.
14 units = 0.14 mL. 0.14 * 2.5 = 0.35 mg. If you cannot reconstruct the diluent
volume for a vial, you cannot reconstruct the dose, which is the argument for
recording the reconstitution at the moment you perform it.

Titration steps

Compounded protocols generally follow the labeled escalation schedules: a low
starting dose held for four weeks, then a step up, with the step held again
before the next increase. Steps exist to let gastrointestinal side effects settle,
not to reach a target quickly. A missed step-up is not an emergency; a doubled
step is a bad week. Recording the date each step began is what makes a plateau
distinguishable from a stall.

Half-life and timing

Semaglutide has a terminal half-life of roughly 7 days, which is what supports
once-weekly dosing and means steady state is not reached for four to five weeks.
Tirzepatide sits near 5 days, also weekly. In practice this means a dose shifted
by a day matters very little, while switching your injection day repeatedly makes
your own side-effect diary uninterpretable. Pick a weekday and keep it.

Injection site rotation

Abdomen (avoiding a two-inch radius around the navel), outer thigh, and back of
the upper arm are the usual subcutaneous sites. Rotate between regions rather
than within one, and leave at least an inch between consecutive sites in the same
region. Repeated injection into one spot produces local lipohypertrophy, which
changes absorption.

What a dose log should record

At minimum, per injection: date and time, compound, dose in mg, the vial's
concentration in mg/mL, the volume or unit count actually drawn, the injection
site, and any side effects in the 48 hours after. Per vial: the labeled peptide
mass, the diluent volume, the reconstitution date, and the storage location.
A GLP-1 dose tracker that stores the vial record alongside
the injection record is what turns "20 units" back into a milligram figure months
later.

Tooling: Peptide Tracker & Calculator is a free iPhone app
that does the reconstitution arithmetic above and keeps the vial and injection
records together.