1 ml U-100 insulin syringes, 30G — pack of 10

Sterile 1 ml insulin syringes with a fixed 30G · 0.3 × 13 mm needle, graduated in 100 units for precise volumetric withdrawal of reconstituted solutions in the laboratory. Pack of 10 single-use units. Laboratory consumable, research use only.

Research areas

• Withdrawal of reconstituted solutions
• Precise volumetric measurement
• Peptide handling in the laboratory

Technical data

Reading a U-100 syringe: IU, millilitres and micrograms

The most widespread error rests on an abbreviation. The graduations of a U-100 syringe are numbered in "units", written IU, and many read them as units of biological activity — like the international unit used for an enzyme or a vitamin. They are not: they are units of volume.

The definition is geometric and unambiguous. "U-100" means the total volume of 1 ml is divided into 100 graduations, which yields a constant equivalence:

1 IU of graduation = 0.01 ml.

It holds for any liquid. Water, a buffer or a reconstituted peptide solution all occupy the same volume at the same mark.

The mass held in those 0.01 ml, however, is not a property of the syringe: it follows from the concentration reached at reconstitution. Depending on the solvent volume added to the vial, one mark can stand for 25 mcg, 250 mcg or 500 mcg. The syringe measures a volume; the vial decides what that volume contains.

The practical consequence: a graduation quoted on its own is incomplete data. "12 IU" only becomes usable alongside the concentration of the solution, in mg/ml or mcg/ml. Each small line is 1 IU, and the 50 mark is exactly half the volume, 0.5 ml. Below 0.05 ml, reading uncertainty becomes significant — reconstituting at a lower concentration moves the draw onto a more legible range.

What 30G and 0.3 × 13 mm mean

The packaging carries two notations for the same needle, in two systems.

30G is the gauge. The scale runs against intuition: the higher the number, the thinner the needle, so a 30G is thinner than a 29G or a 27G. The inversion comes from the origin of the scale, built on the number of successive drawing passes applied to the metal tube. 0.3 × 13 mm states the same needle in millimetres: 0.3 mm outer diameter, the metric equivalent of gauge 30, and 13 mm of metal length.

A fine gauge has a mechanical trade-off: the narrow channel reduces flow. With a slightly viscous solution, aspiration takes a few seconds longer, and forcing the plunger draws in air. A slower gesture is the only correction needed. The needle is fixed to the barrel, with no detachable Luer hub — a design that removes the dead volume of the cone, where a fraction of solution stays trapped on a detachable-needle syringe.

A worked example

Take a 5 mg vial reconstituted with 2 ml of solvent.

• concentration: 5 mg ÷ 2 ml = 2.5 mg/ml, i.e. 2,500 mcg/ml;
• 10 graduations = 0.1 ml;
• 0.1 ml × 2,500 mcg/ml = 250 mcg;
• the vial allows 20 draws of 10 IU.

A pack of 10 covers half of those twenty draws, and two packs cover the whole vial. This is the pack that avoids running out mid-series: ten consecutive draws without interrupting a protocol to restock.

Changing the reconstitution volume changes the graduation, never the mass in the vial. Reconstituting the same 5 mg with 1 ml gives 5 mg/ml, and the 250 mcg are then drawn at 5 IU. For any other combination of mass, volume and syringe capacity, our reconstitution calculator shows the graduation to aim for.

Good withdrawal practice

• A fresh syringe per draw. The tip blunts on its first pass through a septum; a blunt tip cuts the elastomer instead of parting it, releasing micro-fragments into the solution.
• Purge the air before withdrawing the needle. Syringe upright, tip up, flick the barrel, then push the plunger gently. On a 0.1 ml draw, a 0.05 ml bubble halves the accuracy.
• Wipe the septum before each puncture and wait for it to dry.
• Never reuse a needle, even on the original vial minutes later.
• Discard used syringes in a sharps container, per the regulations applicable to the laboratory.

Common mistakes

• Taking IU for units of activity. They are units of volume: 1 IU = 0.01 ml, whatever the contents.
• Passing on a graduation without its concentration. A figure in IU only means something with the concentration of the solution attached.
• Assuming a higher gauge means a thicker needle. The gauge scale is inverted: 30G is thinner than 27G.
• Drawing a volume too small to read. Below 0.05 ml, reading uncertainty grows; a lower reconstitution concentration makes the graduation usable.
• Reusing an already-used syringe. Sterility is compromised and the tip is blunt from the first puncture.