Source of Insulin syringe

{{Infobox concept | name = Insulin syringe | subtitle = Administration device | image = syringe.svg | caption = Graduations are in insulin units; the unit is defined against U-100 insulin, not against volume. | Graduation = Insulin units (U) | U-100 relationship = 100 units = 1 mL | Common sizes = 0.3 mL (30 U), 0.5 mL (50 U), 1.0 mL (100 U) | Needle = Typically 29–31 gauge, 4–12.7 mm }} {{hatnote|For converting between units and millilitres, see [[Insulin syringe unit conversion]].}} An '''insulin syringe''' is a small-volume syringe graduated in insulin units rather than in millilitres. The unit is a measure of insulin activity, and the graduation scale is derived from the U-100 concentration convention in which 100 units of insulin occupy 1 mL.{{r|ada2024}} For any substance that is not U-100 insulin, the unit markings are therefore simply a volume scale in which one mark equals 0.01 mL. This is the whole of the conversion, and it is the source of most of the confusion surrounding these devices when they are used for other preparations. See [[Insulin syringe unit conversion]].{{r|usp797}} Their prevalence in this context follows from the volumes involved. A dose of a few hundred micrograms of a peptide at a few milligrams per millilitre is a volume of tens of microlitres, which a 1 mL syringe measures poorly and a 0.3 mL syringe measures adequately.{{r|iso7886}} == Graduations and accuracy == A 0.3 mL syringe is graduated in single units, sometimes in half units; a 1.0 mL syringe usually in two-unit increments. Finer graduations on a smaller barrel give better resolution for small volumes, which is why barrel size is chosen to suit the volume rather than for convenience.{{r|iso7886}} Accuracy standards for syringes specify tolerances as a percentage of nominal volume, so absolute error is smaller on a smaller syringe. Measuring 5 units in a 100-unit barrel is measuring at 5% of full scale, where both the tolerance and the reading error are large relative to the quantity. [[Syringe dead space|Dead space]] — the volume retained in the hub and needle after the plunger is fully depressed — is a separate consideration and is proportionally larger for small doses. Low-dead-space designs reduce it substantially.{{r|iso7886}} == The unit convention == | Syringe marking | Volume | At 5 mg/mL | At 2.5 mg/mL | |---|---|---|---| | 5 U | 0.05 mL | 250 μg | 125 μg | | 10 U | 0.10 mL | 500 μg | 250 μg | | 20 U | 0.20 mL | 1,000 μg | 500 μg | | 40 U | 0.40 mL | 2,000 μg | 1,000 μg | The table is arithmetic, not guidance. It illustrates that a syringe marking corresponds to a mass only through a concentration, and that the concentration is itself uncertain unless the actual peptide mass in the vial is known — see [[Reconstitution of lyophilised peptides]] and [[Peptide content]].{{r|usp1503}} The historical U-40 and U-500 insulin concentrations, with syringes scaled to match, are the reason the unit convention exists at all and the reason mismatched syringe and concentration have caused documented harm in insulin therapy. That history is why the convention is worth understanding rather than working around.{{r|ada2024}} == Needles == Needle gauge and length are chosen for the route. Subcutaneous administration uses short fine needles, typically 4–8 mm and 29–32 gauge in current practice; longer needles increase the chance of intramuscular delivery, which changes absorption. See [[Subcutaneous injection]].{{r|ada2024}} Fine needles are more comfortable but deliver more slowly and are more easily bent or blunted. A needle used once is sharp; a needle reused is not, and blunting is measurable after a single insertion. Disposal is regulated as sharps waste in most jurisdictions, and disposal in household refuse is prohibited in many. See [[Sharps disposal]].{{r|usp797}} Nothing on this wiki is medical advice, and research-use compounds are not approved for human administration.{{r|usp797}} == References == {{reflist}} <ref name="ada2024">American Diabetes Association. "Facilitating positive health behaviors and well-being to improve health outcomes: Standards of Care in Diabetes." ''Diabetes Care'' 47(Suppl 1) (2024).</ref> <ref name="iso7886">ISO 7886-1:2017, ''Sterile hypodermic syringes for single use — Part 1: Syringes for manual use''.</ref> <ref name="usp797">United States Pharmacopeia, General Chapter <797>, ''Pharmaceutical Compounding — Sterile Preparations''.</ref> <ref name="usp1503">United States Pharmacopeia, General Chapter <1503>, ''Quality Attributes of Synthetic Peptide Drug Substances''.</ref> == See also == * [[Insulin syringe unit conversion]] * [[Syringe dead space]] * [[Subcutaneous injection]] * [[Sharps disposal]] * [[Reconstitution of lyophilised peptides]] {{DEFAULTSORT:Insulin syringe}} [[Category:Injection technique]] [[Category:Clinical practice]] [[Category:Unit conversion]]