What it is
A hypodermic needle is a thin, hollow metal tube with a sharpened tip. The other end is fixed into a small connector, called a hub, that fits onto a syringe or a length of medical tubing. “Hypodermic” means “under the skin”.
Needles are sized by gauge. The higher the gauge number, the thinner the needle. For single-use needles an international standard gives each diameter its own colour code so that sizes can be told apart at a glance, although the standard itself says the colour does not replace checking the printed size.
Most needles in use today are stainless steel, come sterile, and are labelled for one use only. Reusable needles, built to be cleaned and sterilised between uses, were once standard in medicine; single-use equipment, sterile each time, is now the norm.
The FDA identifies a hypodermic single-lumen needle (21 CFR 880.5570) as a device that injects fluids into, or withdraws fluids from, tissue below the skin surface, consisting of a metal tube sharpened at one end and joined at the other to a female connector (hub) that mates with the male nozzle of a piston syringe or an intravascular administration set. The piston syringe is a separate device (21 CFR 880.5860).
Three ISO standards define the basic product. ISO 9626:2016 specifies dimensions and mechanical properties (stiffness, resistance to breakage, corrosion resistance) of rigid stainless-steel needle tubing from 3.4 mm (10 G) to 0.18 mm (34 G). ISO 7864:2016 sets requirements and test methods for sterile single-use hypodermic needles of 0.18 to 1.2 mm; dental needles and pen needles are excluded and covered by their own standards. ISO 6009:2016 assigns colour codes to designated metric sizes from 0.18 to 3.4 mm and states that colour coding does not absolve the user from checking the marked size. ISO 23908 covers sharps-injury protection features. Both ISO 7864 and ISO 9626 are currently under revision.
Who made it and when
The hollow needle is usually credited to Francis Rynd, a Dublin surgeon, who in 1844 used one to deliver a pain-relieving solution under a patient’s skin. In 1853 two doctors working separately, Alexander Wood in Edinburgh and the French surgeon Charles-Gabriel Pravaz, joined a fine hollow needle to a syringe. Wood’s syringe had glass sides, which let the doctor see how much liquid was inside, and he is credited with the modern hypodermic syringe.
For about a century needles and glass syringes were cleaned, sterilised and used again. Mass-produced disposable needles arrived in the mid-1950s: the Smithsonian records that Roehr Products of Connecticut began making them in 1955, and by 1960 the firm was described as the leading maker of disposable needles and sterile disposable syringes.
Rynd introduced a morphine solution beneath the skin through a hollow cannula at the Meath Hospital, Dublin, in 1844, and published the method in 1845. Pravaz’s syringe of 1853 was made of silver and driven by a screw rather than a plunger; it was designed for injecting a coagulant (iron perchloride) into aneurysms. Wood, in Edinburgh, injected morphine near painful sites in 1853 and published his method in the Edinburgh Medical and Surgical Journal in 1855. The word “hypodermic” is generally attributed to Charles Hunter, who argued against Wood that injected drugs acted throughout the body rather than only where they were placed (Brunton, 2000).
The National Museum of American History records that Roehr Products (Waterbury, Connecticut) began manufacturing disposable hypodermic needles in 1955, and introduced the Monoject name in 1957. National Museums Scotland notes that reusable syringes spread disease before antisepsis was understood and were later sterilised between uses, and that single-use equipment ensures sterility for each use. Kotwal’s 2005 review notes that injection safety guidelines are now clear in high-income countries, while countries where injections arrived in the early twentieth century carry most of the remaining risk from unsafe injections.
What the data say
The strongest safety evidence is about reuse between people. The CDC’s rule is “One Needle, One Syringe, Only One Time”: once used, the needle and the syringe are both contaminated. CDC researchers reported that since 2001 nearly 200,000 US patients have been notified, and offered testing, after possible exposure to contaminated injection equipment or medicines. Worldwide, unsafe injections still caused an estimated 1.7 million hepatitis B infections in 2010.
Reuse by the same person has been studied mainly in people with diabetes who inject insulin. One small study found no progressive damage to the tip over four or five uses. Reviews, however, link reuse with fatty lumps under the skin and with more pain, and they note that the underlying studies are at high risk of bias.
Cross-patient reuse: Schaefer et al. (CDC, 2020) catalogued 38 US patient-notification events from 2012 to 2018 covering more than 66,748 patients; 25 involved syringe or needle reuse in routine care, and 11 had documented outbreak-associated hepatitis B or C infections. With the 2001–2011 review, nearly 200,000 patients had been notified. Pépin et al. (2014) modelled infections from unsafe injections in 2010 at 16,939–33,877 HIV, 157,592–315,120 hepatitis C and about 1.68 million hepatitis B, reductions of 83–91% from 2000.
Same-person reuse: Puder et al. (2005) found no progressive tip deformity on electron microscopy and no rise in pain over four to five uses of insulin pen needles (270 injections). A 2016 systematic review of 25 studies, all at high risk of bias, found no association with injection-site infection but pooled cross-sectional data linking reuse with lipohypertrophy (risk difference 0.16) and more perceived pain; it concluded there is no clear evidence for or against. A later meta-analysis of 51 studies, partly authored by employees of a pen-needle maker, reported a prevalence odds ratio of 3.20 (95% CI 1.99–5.13) for lipohypertrophy with reuse.
Regulatory picture
In the US, needles are medical devices, not drugs. The FDA puts the ordinary hypodermic needle in Class II, its middle-risk tier, and a maker needs FDA clearance through a premarket notification, called a 510(k), before selling one. Clearance is not the same as FDA approval. The FDA points manufacturers to international standards for needle tubing, sterile single-use needles and colour coding. A single-use needle that is commercially reprocessed for reuse is classed as a separate product that needs its own clearance.
Workplace rules come from the Needlestick Safety and Prevention Act of 2000, which requires US employers to consider and adopt safer needle designs. For households, the FDA says used needles belong in a sharps disposal container and never loose in the trash, in recycling or down the toilet.
Product code FMI (needle, hypodermic, single lumen) sits under 21 CFR 880.5570, Class II (performance standards), with a 510(k) required and no exemption; the piston syringe (21 CFR 880.5860, code FMF) is also Class II. FDA’s classification record lists ISO 7864, ISO 9626, ISO 6009, ISO 23908 and ISO 80369-7 (small-bore connectors) among recognised consensus standards. Reprocessed single-use needles carry a separate product code (NKK) with their own 510(k) requirement, and sharps disposal containers (code MMK) are classified under the same section.
Public Law 106-430, signed on 2000-11-06, directed OSHA to amend the Bloodborne Pathogens Standard (29 CFR 1910.1030) to define sharps with engineered sharps-injury protections, require annual consideration of safer devices in exposure control plans, and add a sharps injury log and non-managerial employee input. Congress’s findings cited 600,000 to 800,000 needlestick and percutaneous injuries a year and a CDC estimate that 62–88% of sharps injuries could potentially be prevented with safer devices. In December 2023 the FDA reported counterfeit needles of unconfirmed sterility packaged with counterfeit Ozempic pens.
