Glossary

Bacteriostatic water

Also: BAC water, BAC, bac water

Sterile water containing 0.9% benzyl alcohol as a preservative. Used to reconstitute peptide vials because the preservative allows multiple draws from the same vial over days or weeks without bacterial contamination. Abbreviated BAC water.

Bioavailability

Also: bioavailability (F), F

The fraction of an administered dose that actually reaches your bloodstream. Subcutaneous injections typically have 80-100% bioavailability. Oral medications are often much lower because they're partially broken down in the gut and liver first.

Cmax

Also: peak concentration, peak level, peak

Peak concentration — the highest level of medication in your blood after a dose. Where you are on the curve when the medication is at its strongest.

Ester

Also: ester chain, esterified

A chemical modification attached to a hormone molecule that controls how slowly it's released into your bloodstream. Longer esters (like cypionate or undecanoate) release more slowly, meaning longer half-lives and less frequent injections. The ester is cleaved off in the body, releasing the active hormone.

Half-life

Also: half life, t½, elimination half-life

The time it takes for the concentration of a medication in your blood to drop by 50%. A medication with a 7-day half-life still has 25% remaining after 14 days. Not the same as 'how long it lasts' — effects can persist well beyond one half-life.

Intramuscular

Also: IM, intramuscular injection

An injection into muscle tissue. Common sites: vastus lateralis (outer thigh), ventrogluteal (hip/glute), deltoid (shoulder). Used for most testosterone esters and some estradiol preparations. Abbreviated IM.

Pharmacokinetics

Also: PK, pharmacokinetic

The study of how your body absorbs, distributes, metabolises, and eliminates a medication over time. In practical terms: the math that predicts your medication levels between doses. Abbreviated PK.

PIP

Also: post-injection pain, post injection pain, injection site pain

Post-Injection Pain — soreness, swelling, or discomfort at the injection site after administration. Can be caused by the carrier oil, injection technique, needle gauge, or the compound itself. Usually resolves within 1-3 days.

Protocol

Also: dosing protocol, treatment protocol, regimen

A structured dosing plan that defines what you take, how much, how often, and for how long. Can range from a simple single-medication schedule to a complex multi-compound regimen with bloodwork checkpoints.

Reconstitution

Also: reconstitute, reconstituting

The process of adding a solvent (usually bacteriostatic water) to a lyophilized (freeze-dried) powder to create an injectable solution. Common for peptides like BPC-157, CJC-1295, and TB-500. The ratio of powder to water determines the concentration.

Steady state

Also: steady-state, Css

The point where the amount of medication entering your body equals the amount being eliminated, so your peak and trough levels stabilise into a predictable pattern. Typically reached after 4-5 half-lives of consistent dosing.

Subcutaneous

Also: SubQ, SC, sub-Q, subcutaneous injection

An injection into the fat layer just beneath the skin. Common sites: abdomen, thigh, upper arm. Used for most GLP-1 medications, many peptides, and some hormone preparations. Abbreviated SubQ or SC.

Titration

Also: titrate, dose titration, titration schedule

A gradual, step-wise increase in dose over weeks or months to reach the target dose while minimising side effects. Standard practice for GLP-1 medications (e.g., Ozempic starts at 0.25mg and increases to 1-2mg over several months).

Tmax

Also: time to peak, time to Cmax

Time to peak concentration — how long after administration the medication reaches its highest level in your blood. For subcutaneous injections, this is typically hours to days depending on the medication.

Trough

Also: trough level, Cmin, nadir

The lowest concentration of medication in your blood, typically measured right before your next dose. Trough levels are the most common timing for bloodwork because they show your minimum effective level.