Dosing terms, explained

mcg (microgram)

One millionth of a gram. 1,000 mcg = 1 mg. Many peptide amounts are quoted in mcg, and mixing up mcg and mg is a common, serious error.

mg (milligram)

One thousandth of a gram. 1 mg = 1,000 mcg. Vials are usually labelled in mg.

IU (international unit)

A unit based on biological activity rather than weight, used for some hormones such as HCG and growth hormone. IU cannot be converted to mg without the conversion for that specific substance.

ml and cc

Millilitre, a volume. 1 ml is the same as 1 cc (cubic centimetre).

Unit (on a syringe)

A mark on an insulin syringe. On a U-100 syringe, 100 units = 1 ml, so 1 unit = 0.01 ml. A unit measures volume, not how much peptide you get; that depends on how the vial was mixed.

U-100 syringe

The most common insulin syringe scale: 100 units per ml. U-40 syringes (40 units per ml) also exist and look similar.

Reconstitution

Dissolving a freeze-dried powder in a liquid so it can be drawn into a syringe. Also called mixing. See the mixing and injecting guide.

Lyophilised (freeze-dried)

Dried by freezing and removing the water under vacuum. Many peptides are supplied this way because the powder keeps better than a liquid.

Bacteriostatic water (BAC water)

Sterile water with 0.9% benzyl alcohol as a preservative, used to mix vials that will be punctured more than once.

Sterile water

Water with no microorganisms and no preservative. Usually meant for a single use once opened.

Concentration (strength)

How much peptide is in each ml of the mixed solution, e.g. mcg per ml. It depends on the vial amount and the water added.

Subcutaneous (subQ, SC)

An injection into the fatty layer just under the skin, typically on the belly, thigh or back of the arm.

Intramuscular (IM)

An injection into a muscle. Uses a longer needle than a subcutaneous injection.

Intranasal

Taken as a nasal spray or drops, as with Semax and Selank.

Oral and troche

Swallowed (oral), or a troche: a lozenge that dissolves in the mouth or against the gum.

Dose

The amount taken at one time.

Frequency

How often a dose is taken, e.g. once a day or three times a week.

Cycle

A planned period of use followed by a break, e.g. “8 weeks on, 4 weeks off”.

5 on, 2 off

A common schedule: five days of use followed by two days without, repeated weekly.

Titration

Starting with a low amount and increasing it step by step, as in the GLP-1 trials (for example every 4 weeks).

Half-life

The time it takes for the amount in the body to fall by half. It shapes how often something has to be taken.

Loading (front-loading)

Using a higher amount or frequency at the start before dropping to the usual schedule.

Microdosing

Using much smaller amounts than the standard or trial doses, often more frequently.

Stack

Two or more compounds used together, e.g. BPC-157 with TB-500, or CJC-1295 with ipamorelin.

Blend

A single vial that contains more than one peptide. The split between them is not always stated.

GH secretagogue

A substance that prompts the pituitary gland to release more of the body’s own growth hormone, e.g. ipamorelin, sermorelin or MK-677.

GHRH analogue

A copy or variant of growth-hormone-releasing hormone, e.g. sermorelin, tesamorelin and CJC-1295.

GLP-1 receptor agonist

A medicine that mimics the gut hormone GLP-1, reducing appetite and helping blood-sugar control, e.g. semaglutide. Tirzepatide and retatrutide also act on other receptors.

Research peptide (research use only)

A product sold as a laboratory chemical, not as an approved medicine. It is not checked by a medicines regulator for identity, purity or sterility.

COA (certificate of analysis)

A document from a lab reporting what a batch was tested for and the results, such as purity by HPLC and identity by mass spectrometry.

HPLC

High-performance liquid chromatography: a lab test often used to measure a peptide’s purity.

Placebo-controlled trial

A study in which one group gets the real substance and another gets a dummy, so that real effects can be told apart from expectation and chance.

Related: Mixing and injecting guide · Comparisons · reconstitution maths at peptidecalculator.eu