Essential Guides

Knowledge · Essential Guides

The handling knowledge thatapplies to every vial.

Independent of which compound is inside it. Reconstitution, syringes and units, storage and stability, reading a certificate, and the vocabulary.

Guide 01

Reconstitution

Lyophilised peptide is a dry cake under vacuum. Adding liquid is the single point in handling where you can destroy the material without any visible sign that you have.

Choosing a diluent

Diluent	Preservative	Multi-draw?	Typical use
Bacteriostatic water	0.9% benzyl alcohol	Yes	Default for any vial drawn from more than once
Sterile water for injection	None	No — single use	Single-draw work, or where benzyl alcohol interferes
0.9% sodium chloride	None (unless bacteriostatic NaCl)	No	Occasionally specified for particular compounds
Acetic acid 0.6%	None	No	Poorly soluble peptides that will not go into water

Bacteriostatic Water for Injection USP carries an FDA label warning that benzyl alcohol is associated with toxicity in neonates and must not be used in that population.

Technique

Let the vial warm. A vial straight from the freezer will pull condensation onto the cake.
Swab both stoppers. Diluent vial and peptide vial, 70% isopropyl, let it dry.
Draw the diluent and, before injecting, allow the peptide vial's vacuum to assist — do not fight it.
Aim at the glass. Angle the needle so the stream runs down the inside wall. A jet directly onto the cake shears the peptide.
Swirl, do not shake. Roll the vial between your palms. Foam means you have introduced shear and air — both bad.
Wait. Most cakes dissolve in 30 seconds to a few minutes. If it is still cloudy after ten minutes at room temperature, something is wrong with the material.
Label it. Compound, strength, volume added, resulting concentration, date. The number you will want in three weeks is the concentration, not the volume.

How much water?

There is no correct answer, only a trade-off. Less water gives a concentrated solution and tiny draws — precise on paper, imprecise in practice, because a half-unit error on a 3-unit draw is a 17% error. More water gives comfortable 10–30 unit draws and better repeatability, at the cost of needing a vial that physically holds the volume. As a rule of thumb, choose the volume that puts your intended draw between 10 and 40 units. The calculator will solve this for any vial in seconds.

Mixing more than one vial at a time

A reconstituted vial keeps for about 28 days, and nothing in that says the vials have to be mixed one by one as you reach them. If a batch will be finished inside the window, mix the batch in one sitting. It is the difference between one tidy session with everything laid out and a rushed two minutes every other evening — and it leaves the injection as the only thing handled day to day.

The arithmetic is the same every time: how many days does one vial cover, and how many of those fit inside 28?

If one vial covers	28 days is
2 days	14 vials
4 days	7 vials
7 days	4 vials
14 days	2 vials

The clearest case is a short course that finishes well inside the window. A twenty-day course getting through half a vial a day is ten vials, all of it gone eight days before the window closes — so there is no reason to mix it in anything other than one go.

Two things to get right when batching

Size the batch to the window, not to the box. The clock starts the moment the water goes in, and it starts on every vial in the batch at once. Mix what will be used before day 28 and leave the rest dry — a sealed vial is not on the clock at all. A six-week course is usually two batches rather than one.

Date every vial at the bench. Fourteen identical vials on a fridge shelf is precisely the situation where you lose track of which went in when. Label as you go, in the moment, not afterwards.

Guide 02

Syringes & Units

The most consequential misunderstanding in this entire field is the belief that a "unit" is an amount of peptide. It is not. It is a volume.

An insulin syringe marked U-100 is calibrated for insulin at 100 international units per millilitre. The barrel markings are therefore just hundredths of a millilitre with an insulin-specific label on them. One unit = 0.01 mL. Always. Regardless of what is dissolved in it.

How much peptide sits in that 0.01 mL depends entirely on how much water you added. The same 10 mg vial delivers 100 mcg per unit at 1 mL, or 20 mcg per unit at 5 mL — a fivefold difference from the same vial. "Take 10 units" is a meaningless instruction unless the concentration travels with it.

Units	Volume	At 5 mg/mL	At 10 mg/mL	At 2 mg/mL
5 u	0.05 mL	250 mcg	500 mcg	100 mcg
10 u	0.10 mL	500 mcg	1,000 mcg	200 mcg
20 u	0.20 mL	1,000 mcg	2,000 mcg	400 mcg
50 u	0.50 mL	2,500 mcg	5,000 mcg	1,000 mcg
100 u	1.00 mL	5,000 mcg	10,000 mcg	2,000 mcg

Barrel size changes the resolution, not the scale

A 0.3 mL U-100 syringe holds 30 units and prints a mark every half unit. A 1 mL holds 100 units and prints every unit or two. The unit is identical in both — the smaller barrel simply lets you read it more finely. For draws under about 20 units, the 0.3 mL barrel is the better instrument.

Guide 03

Storage & Stability

State	Temperature	Typical stability	Notes
Lyophilised	−80 °C	~2 years	Supplier long-term condition
Lyophilised	−20 °C	~1 year	Practical long-term storage
Lyophilised	2–8 °C	Months	Fine for working stock
Lyophilised	Room temp	Weeks, dark & dry	Shipping tolerance, not storage
Reconstituted (bacteriostatic)	2–8 °C	Commonly cited ~28 days	Convention, not a stability study
Reconstituted (sterile water)	2–8 °C	24–48 hours	No preservative

Honest caveat: for most research peptides, no published forced-degradation or long-term stability study of the reconstituted solution exists. The 28-day figure is a handling convention that has become repeated as though it were data. We report it as a convention.

Freeze–thaw

Do not freeze reconstituted solution. Ice-crystal formation concentrates solutes at the freezing front and drives aggregation; each cycle costs potency you cannot see. Freezing applies to the dry cake only, and repeated freeze–thaw of powder should be avoided by aliquoting before the first freeze.

Recognising degradation

Cloudiness or haze after a solution was previously clear — aggregation.
Visible particulates or strands — discard.
Colour change. Most peptide solutions are colourless. GHK-Cu is the exception: it should be distinctly blue, and loss of that blue means the copper complex has broken down.
A cake that will not dissolve in ten minutes at room temperature.

Guide 04

Reading a Certificate of Analysis

A COA answers three separate questions, and vendors routinely conflate them.

Identity

Mass spectrometry. Does the observed molecular weight match the expected one? This is the question that catches a mislabelled vial.

Purity

HPLC, usually reported as area percent at 214 or 220 nm. What fraction of the peptide present is the intended sequence rather than truncations and deletions.

Peptide content

The one almost nobody prints — what fraction of the vial's mass is peptide rather than counter-ion salt and residual water.

The salt-mass problem

Synthetic peptides are usually isolated as acetate or trifluoroacetate salts, and a lyophilised cake also holds residual water. Peptide content is commonly 70–90% of gross mass. A vial labelled 10 mg at 80% net peptide contains 8 mg of the actual compound — a 20% error in every calculation downstream of it, silently. When peptide content is stated, use it. When it is not, understand that your concentration is an upper bound.

A second identity question matters for one compound in particular. Material sold as TB-500 may be the seven-amino-acid fragment Ac-LKKTETQ (889 Da) or full-length thymosin β4 (~4,963 Da). Same label, same milligram figure, 5.6× difference in molar quantity, and essentially all the published biology used the full-length protein. Check the molecular weight on the COA, not the product name. We flag this on the GLOW profile rather than leaving you to find out.

See our certificates of analysis

Guide 05

Glossary

Term	Meaning
Lyophilised	Freeze-dried under vacuum. The dry "cake" in the vial; stable far longer than solution.
Bacteriostatic water	Sterile water with 0.9% benzyl alcohol as a preservative, allowing repeat draws from one vial.
Reconstitution	Dissolving the lyophilised cake back into liquid.
U-100	Syringe calibration where 100 units = 1 mL. One unit is always 0.01 mL.
Half-life (t½)	Time for plasma concentration to fall by half. Drives how often something is administered.
Bioavailability (%F)	Fraction of a dose reaching systemic circulation by a given route, relative to intravenous.
Agonist	Binds a receptor and activates it. An antagonist binds and blocks.
Titration	Stepping an amount up gradually. For incretin compounds this is a tolerability strategy, not a formality.
Preclinical	Cell culture and animal work, before any human administration.
Phase 1 / 2 / 3	Human trial stages: safety and PK · efficacy signal and dose-finding · large confirmatory.
Peptide content	Fraction of a vial's mass that is peptide rather than salt and water. Typically 70–90%.
HPLC	High-performance liquid chromatography — the purity assay on a certificate of analysis.
WADA S0	Prohibited-list category for substances with no regulatory approval anywhere. Banned at all times.

Research use only

For laboratory research use only. Not for human or veterinary use. Not intended to diagnose, treat, cure, or prevent any disease. Nothing in these guides is medical advice or a direction to administer any compound to any person.

For laboratory research use only. Not for human or veterinary use. Not intended to diagnose, treat, cure, or prevent any disease.