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Every bit of jargon, translated

Supply listings are written in shorthand. Here's what the words mean, so you can read a product page without a second tab open. These are definitions of terms, not instructions — for anything about your health, ask a licensed clinician.

Liquids you mix with

Bacteriostatic water
Sterile water with 0.9% benzyl alcohol added. The alcohol stops bacteria multiplying after the seal is first punctured, which is why an opened bottle is generally treated as good for about 28 days rather than one sitting. Full comparison →
Sterile water for injection
Water with nothing added. Sterile in the sealed bottle, with no preservative to protect it afterwards, so it's intended for single use.
Benzyl alcohol
The preservative that makes water "bacteriostatic". A small number of people avoid it, which is the main reason plain sterile water is still sold.
Saline / 0.9% sodium chloride
Sterile salt water at 0.9% — the same salt concentration as blood, which is why it's called isotonic. Sold both plain (single-use) and bacteriostatic (preserved).
Reconstitution
Adding liquid to a powder to turn it back into a solution. "Reconstituted" just means mixed. Step by step →
Concentration (mg/mL)
How much substance sits in each millilitre of liquid: total milligrams divided by millilitres of liquid added. Adding more liquid doesn't change how much is in the bottle — it spreads the same amount across more volume, which makes small amounts easier to measure.
mcg and mg
A microgram (mcg or µg) is one thousandth of a milligram. 1 mg = 1,000 mcg. Mixing the two up is the single most common arithmetic error in this whole area, so check which unit a label uses.

Syringes and needles

Gauge (G)
Needle thickness, counted backwards: a bigger number is a thinner needle. 31G is hair-thin; 18G is thick and generally used for drawing liquid, not injecting. Sizes decoded →
U-100 and "units"
Insulin syringes are marked in units instead of millilitres. On any standard U-100 syringe, 100 units = 1 mL, so 10 units is 0.1 mL — the same on every barrel size.
Barrel size (0.3 / 0.5 / 1.0 mL)
How much the syringe holds. A smaller barrel spreads the same markings over more space, so small amounts are easier to read accurately.
Half-unit syringe
A syringe marked every half unit rather than every unit — worth having when a measurement keeps landing between two lines.
Luer-lock and luer-slip
The two ways a needle attaches. Luer-lock screws on with a thread and won't pop off under pressure; luer-slip just pushes on. Filters and adapters are made for luer-lock.
Blunt fill needle
A wide needle with a deliberately blunt tip, for drawing liquid out of a vial quickly. The blunt tip makes an accidental stick far less likely, which is the point — but it is still a sharp, it will go through skin under force, and it belongs in the sharps container like any other needle.
Dead space
The liquid left behind in the needle and tip after the plunger is fully down. "Low dead space" designs waste less of it — which matters more the more expensive the contents.
Pen needle
A short screw-on needle for injection pens rather than syringes. Usually 32G, and 4 mm is the common length.

Keeping things clean

Sterile vs. clean
"Sterile" is a manufacturing claim: the item was processed to be free of living organisms and sealed that way. It applies until the seal is opened. "Clean" is just clean.
Alcohol prep pad
A sealed wipe of 70% isopropyl alcohol. 70% is the standard strength — stronger isn't better, because some water content helps it work.
Chlorhexidine
An antiseptic used instead of alcohol, often on skin that alcohol has dried out or irritated.
0.22 micron filter
A filter fine enough to hold back bacteria, sold as a small disc that screws onto a luer-lock syringe. The standard "sterilising grade" pore size in labs.
Sharps
Anything that can pierce skin — needles, syringes with needles attached, lancets. They go into a certified rigid sharps container (FDA-cleared in the US; BS 7320 or AS 4031 elsewhere), never loose into a bin. Disposal routes →
Coring
Punching a small fragment out of a vial's rubber stopper so it drops into the liquid. A blunted or reused needle makes it much more likely, which is one of the practical reasons a fresh needle matters.
Parafilm
A stretchy laboratory film wrapped around a cap or stopper as an extra seal against moisture and dust.

Vials and bottles

Vial, stopper and crimp
The glass bottle, the rubber disc you draw through, and the metal ring holding it on. You pierce the stopper rather than removing it.
Ampoule
A sealed glass container with a narrow neck you snap off, rather than a rubber stopper. Single-use by design.
Vial adapter
A plastic spike that seats onto a stopper once and leaves a screw-on port, so you can draw without a needle and without making a new hole each time.
Multi-dose vs. single-dose
Whether a container is intended to be drawn from repeatedly or opened once and finished. It's determined by what's in it — chiefly whether there's a preservative — not by its size.

Cold, storage and travel

Cold chain
The unbroken run of correct temperature from where something was made to where it's used. "Breaking the cold chain" means it warmed up somewhere along the way.
2–8 °C (36–46 °F)
Ordinary refrigerator range, and the storage target printed on most temperature-sensitive products. Always follow the labeling of the specific thing you're storing. Proving your fridge holds it →
Min/max thermometer
A thermometer that records the coldest and warmest it has been since you last reset it — which is how you find out what happened overnight.
Excursion
The industry word for a period spent outside the intended temperature range.
Evaporative cooling wallet
A pouch with crystals you soak in water; as the water evaporates it holds the contents cool for a day or two. No freezer, no ice packs — the trick insulin users use for travel.
Compressor vs. thermoelectric cooler
A compressor cooler works like a real fridge and holds a set temperature. A thermoelectric one only cools a fixed amount below the surrounding air, so on a hot day it may never get cold enough.

Comfort

Lidocaine cream
A topical anaesthetic applied ahead of time to numb skin. 4% is the strongest concentration allowed over the counter for general skin use in the US, and the FDA has warned about stronger over-the-counter versions.
Vapocoolant
A spray that numbs by chilling the skin for a few seconds rather than by any drug. The trick clinics use.
Site rotation
Using a different spot each time rather than the same one repeatedly, which is standard practice to avoid soreness and lumps building up in one place.