Written and maintained by CASRAI Editorial Board
Last updated
This page describes products and general use; it is not medical advice.
A low dead space syringe is a syringe, or a syringe and needle combination, built so that very little fluid stays behind in the device after the plunger is fully pressed. Dead space belongs to the whole assembly (barrel, plunger tip, hub and needle), not to the syringe alone, which is why the same syringe can measure differently with different needles. Typical users are staff in vaccination programmes and clinics, buyers who specify syringes, and harm-reduction services.
What a low dead space syringe is (and what dead space means)
Syringe dead space, also called dead volume, is the amount of fluid left in the syringe and needle after an injection is completed. A low dead-volume (LDV) syringe or needle is designed to reduce that leftover fluid. A harm-reduction booklet from the National Institute for Health and Care Research (NIHR) describes dead space as the space between the needle and the plunger when the plunger is pushed all the way down, and notes that residual blood left in that space could contain viruses such as HIV or hepatitis C if equipment is accidentally shared. Less dead space means less residual fluid in both settings: less wasted medicine and less retained blood.
How it is built
Two design features account for most of the reduction. A modified syringe has a plunger tip molded to the luer cone, so fluid is cleared from the syringe tip as the plunger travels forward. A detachable LDV needle has an extension that fits through the opening of some standard syringes, which reduces the space behind the needle. A fixed (“all in one”) design combines needle and syringe in one device. A conventional high dead-volume needle and syringe is the baseline these designs are compared against.
Types and variants
| Type | Typical use | Key difference |
|---|---|---|
| High dead-volume needle and syringe | Baseline conventional device | Fluid remains in the syringe tip and needle hub after the plunger is fully pressed |
| LDV modified syringe | Used with a standard needle | Plunger molded to the luer cone so fluid is cleared from the syringe tip |
| LDV detachable needle | Fitted to some standard syringes | Needle extension passes through the syringe opening, reducing dead space |
| LDV fixed “all in one” needle and syringe | Single-piece device | Needle is permanently attached to the syringe |
Source: Pfizer-BioNTech information sheet on low dead-volume syringes and needles, hosted on the Government of Canada COVID-19 vaccine site (adapted there from Zule et al., 2018).
Dead-volume values that matter
Dead space is small but varies several-fold between devices. The brand-specific values below are examples of measured results (not a ranking) reported in a 2022 narrative review of syringe performance against ISO 7886-1:2017 (Krisdiyanto et al., Medicine, 101(49):e31812).
| Device as tested | Mean dead space (mL) |
|---|---|
| VanishPoint fixed 25G x 1 inch needle with 1 mL syringe | 0.0103 |
| DPS 1 mL syringe without needle | 0.0104 |
| BD 1 mL syringe without needle | 0.0343 |
| BD 3 mL syringe without needle | 0.0179 |
| TKMD 21G x 1.5 inch needle without syringe | 0.0742 |
| VanishPoint fixed 23G x 1 inch needle with 3 mL syringe | 0.0750 |
The review also cites a study in which tested devices ranged from 3.2 to 96.7 microlitres of dead space per injection. A needle on its own can hold more than a small syringe on its own, so the combination decides the result. Two 1 mL syringes without needles in the same table differ by more than threefold (0.0104 and 0.0343 mL), so brand and design matter as much as barrel size.
For reference, the review reports the ISO 7886-1 maximum dead space by barrel volume:
| Syringe barrel volume | Maximum dead space (mL) |
|---|---|
| Below 5 mL | 0.07 |
| 5 mL up to 10 mL | 0.075 |
| 10 mL up to 20 mL | 0.10 |
| 20 mL up to 30 mL | 0.15 |
| 30 mL up to 50 mL | 0.17 |
| 50 mL and above | 0.20 |
The review notes that most products met these criteria, but some did not: in one cited experiment, 4 of 5 brands of 5 mL syringes exceeded 0.075 mL, and one of 5 brands of 10 mL syringes exceeded 0.1 mL.
How dead volume is measured
The ISO method converts a mass difference into a volume of distilled water. The Pfizer-BioNTech information sheet describes a practical weighing version: weigh the empty assembled syringe and needle on a balance accurate to 1 microgram, draw up water, press the plunger fully, and weigh again. Grams of water equal millilitres of dead volume. Repeat for six syringes and average the results.
How to choose
- Judge the combination, not the syringe. The review states that dead space depends on the needle and syringe together (see the table above).
- Compare against the ISO 7886-1 limit for the barrel size and check a manufacturer’s low dead space claim against a measured value, since some tested products did not meet ISO criteria.
- Match the requirement to the drug and vial. For the Pfizer-BioNTech COVID-19 vaccine, the information sheet says the combination should have a dead volume of no more than 35 microlitres (0.035 mL) to obtain 6 doses from one vial, and that results above 0.05 mL are not likely to achieve 6 doses. A vial of 6 doses of 0.3 mL each may not yield the sixth dose with standard syringes and needles. This threshold is specific to that vaccine and the 2021 guidance; it is not a general figure for other drugs.
Safe use and handling basics
Follow the manufacturer’s instructions for use for the specific device. The NIHR booklet’s rationale for low dead space needles is reduced retained blood where equipment might be accidentally shared; for workplace exposure to blood, see the CASRAI guide on the bloodborne pathogens standard. Related needle selection topics are covered in the butterfly versus straight needle guide, and wider infusion equipment in the infusion supplies and pump selection guide. Infusion-related consumables are listed in the infusion supplies category.
Common mistakes
- Comparing syringes by barrel size alone and ignoring the needle attached.
- Applying the 0.035 mL vaccine threshold to other drugs or vial sizes.
- Assuming a low dead space label means the ISO limit is met without a measured value.
- Fitting a detachable LDV needle to a syringe without confirming it fits the opening; the needle extension fits only some standard syringes.
Frequently asked questions
What is a low dead space syringe?
It is a syringe, or a syringe and needle combination, designed to leave very little fluid in the device after the plunger is fully pressed. Common designs are a plunger molded to the luer cone, a detachable needle with an extension through the syringe opening, and a fixed needle and syringe.
What is syringe dead space?
Syringe dead space, or dead volume, is the amount of fluid that remains in the syringe and needle after an injection is completed. ISO 7886-1 sets maximum values by barrel volume, for example 0.07 mL for barrels below 5 mL.
Sources
- Information about low dead-volume syringes and/or needles for Pfizer-BioNTech COVID-19 Vaccine, hosted on covid-vaccine.canada.ca (Pfizer-authored sheet, not Health Canada guidance), checked 2026-10-29: covid-vaccine.canada.ca
- Krisdiyanto et al., “The hypodermic syringe performance based on the ISO 7886-1:2017: A narrative review,” Medicine (Baltimore) 101(49):e31812, 9 December 2022, checked 2026-10-29: PubMed Central
- NIHR, “Low dead space needles and syringes: What and why?”, 1 July 2019, posted by IDPC, checked 2026-10-29: idpc.net
