What Is An Injection Needle? How To Handle And Use

What is a Injection Needle?

Injection needle is a type of hollow needle—a thin, hollow medical device—that is typically used in conjunction with a syringe to inject medications or liquids into the subcutaneous tissue or to withdraw fluids from the body.

Why use a hypodermic needle?

Injection needles can precisely control the depth and dosage of medication delivery, reducing the risk of tissue damage. They are suitable for medical scenarios that require rapid, direct medication administration or sampling.

What are their features?

· Sterile: Prevents infections and ensures safe injections.

· Latex-free: Reduces the risk of latex allergies.

· Easily connects to a syringe: Standardized design ensures a tight seal and ease of operation.

· Available in various sizes with color coding: Facilitates quick identification of needle specifications, suitable for different drug viscosities and injection sites.

Structure/Design of the Injection Needle

Hub: The connection part at the rear of the needle, usually made of plastic or metal, which fits and is fixed to the tip of the syringe.

Needle Cannula: A hollow metal tube with a sharp tip, used to penetrate the skin or tissue. It is generally made of stainless steel, with an outer silicone coating to reduce friction.

Cap: A protective sheath that covers the needle tip to prevent contamination or accidental needle sticks. It is mostly made of hard plastic, and some designs allow for one-handed removal.

Selecting the Correct Injection Needle Gauge Sizes

Detailed Explanation of Common Injection Needle Sizes (16G ~ 30G)

Special Specifications Supplement

Ultra-large Needles (12G/14G): Diameter of 2.0 ~ 2.5 mm, used for rapid fluid transfusion in trauma emergencies or peritoneal drainage.

Ultra-fine Needles (31G/32G): Diameter < 0.3 mm, suitable for frequent insulin injections in diabetes or ophthalmic surgeries.

Types of Injection Needles

Classification by Product Technical Characteristics

1.Standard Subcutaneous Injection Needles

General-purpose injection needles suitable for routine subcutaneous, intradermal, and intramuscular injections. The needle body is often made of high-transparency medical polymer, facilitating observation of medication flow; the needle tip is designed with a triangular bevel to reduce puncture resistance. Commonly available specifications range from 25G to 30G (diameter: 0.51 mm to 0.31 mm), with needle lengths from 5 mm to 16 mm, made of medical-grade stainless steel, and compatible with both disposable syringes and reusable devices.

2.Insulin Pen Needles

Short needles specifically designed for insulin pens, to be used with pen injectors. The needles are extremely fine (30G to 32G, diameter: 0.31 mm to 0.23 mm) and short (4 mm to 8 mm), minimizing damage to the subcutaneous fat layer and reducing pain. They are made from ultra-thin, seamless steel tubes, with threaded needle hubs ensuring a seal with the pen cartridge, and are mostly individually packaged as sterile disposables to reduce infection risks associated with reuse.

3.Safety Injection Needles

Needles designed with special features to reduce the risk of needle stick injuries, divided into the following subcategories:

· Retractable Safety Needles: The needle automatically retracts into the syringe or protective sleeve after injection, suitable for public vaccination and medical waste management scenarios.

· Shielded Safety Needles: Equipped with built-in sliding protective sleeves or lever-triggered shields; the operator can cover the needle tip with one hand after withdrawal, commonly used in emergency and hemodialysis environments.

· Self-sheathing Safety Needles: The needle automatically deploys a self-locking sheath upon withdrawal from the body, completely enclosing the needle tip; used primarily in infectious disease departments or for HIV/AIDS patient care.

Needle Gauge Range: Safety needles are generally available in 23G to 27G (diameter: 0.64 mm to 0.41 mm) and their length is adapted to meet routine injection needs (10 mm to 30 mm), with the protective features required to meet ISO 23908 sharp penetration standards.

Classification by Clinical Administration Route

1.Intramuscular Injection

Needles for intramuscular injection deliver medication directly into the muscle tissue. The needle should be inserted at a 90-degree angle to the skin. These needles are usually longer; clinically, 20 to 23 gauge needles are commonly used, with some scenarios also using 25 to 29 gauge needles. Needle lengths are typically 13 mm to 16 mm.

2.Intradermis Injection

Intradermal injections require the medication to be precisely injected into the layer just below the epidermis (between the epidermis and dermis), commonly used in tuberculin tests, allergy tests, and local anesthesia. Needles recommended range from 25G to 30G, with needle diameters from 0.5 mm to 0.3 mm, and lengths from 8 mm to 13 mm. During injection, the needle is inserted at an angle of 10 to 15 degrees relative to the skin.

3.Subcutaneous Injection

Needles for subcutaneous injections are used to deliver medication into the subcutaneous tissue layer between the skin and muscle, commonly used for insulin, hormones, or vaccines. Medications administered via this route are absorbed relatively slowly, with some taking up to 24 hours for complete absorption. Common needle specifications are 25G to 30G, with lengths typically ranging from 4 mm to 8 mm.

4.Intravenous Injection

Needles for intravenous injection directly inject the medication into the vein, entering the bloodstream for rapid effect. They are widely used in emergencies (such as in poisoning or myocardial infarction) or treatments that require rapid administration. Typically, 20 to 25 gauge needles are used, with the length adjusted according to the depth of the vein, ensuring the proper balance between puncture depth and flow rate.

IV. Best Practices for Handling and Disposal

Safe Injection Techniques

First and foremost, strict adherence to sterile technique is crucial. Before injection, inspect the syringe and needle for seal integrity and expiration date. Thoroughly disinfect the injection site with 75% alcohol or povidone-iodine, and allow the disinfectant to naturally dry for at least 30 seconds before proceeding.

During the injection process, it is forbidden to remove the needle cap with bare hands, to avoid contact with the needle body or tip, and to always adhere to the "one needle, one medication" principle—eliminating reuse or cross-use of syringes and needles.

After injection, the needle should be immediately detached from the syringe (for products designed for separation). If separation is not possible, the entire assembly should be disposed of in an appropriate sharps container. When performing multiple injections, change gloves promptly and thoroughly disinfect hands.

For special medications (such as biological agents or chemotherapeutic drugs), pre-filled syringes or low-adsorption material needles should be used to reduce drug residue. Additionally, when administering high-risk medications, wear double gloves, safety goggles, and other protective gear throughout the process.

Needle Stick Injury Prevention

Preventing needle stick injuries relies on standardized procedures and a strong safety awareness.

Healthcare professionals should prioritize needles equipped with automatic protective devices (such as shielded needles or self-sheathing needles) and activate the protective mechanism immediately after injection. When withdrawing the needle, use a one-handed technique combined with a fixture to secure the cap, avoiding direct contact with or the passing of exposed needles.

In routine practice, emphasize management of high-risk procedures, and prohibit bending, cutting, or handling discarded needles with bare hands. At the same time, use standardized puncture-resistant gloves and protective gear, and conduct regular emergency drills for needle stick injuries—mastering the standardized process of "compress the wound - rinse with saline - disinfect - report" to minimize occupational exposure risks.

Disposal and Contamination Prevention

Proper disposal of medical waste and contamination prevention serve as the final safety barriers.

All discarded needles must be segregated into puncture-resistant, leak-proof yellow sharps containers. When the container reaches 3/4 capacity, it should be sealed and replaced promptly. Infectious needles must be double-bagged, clearly labeled with "biohazard", and handed over to certified agencies for centralized treatment.

If a needle becomes detached or contaminated, immediately spray the affected area with a chlorine-based disinfectant and let it stand for more than 10 minutes, then thoroughly wipe and disinfect the area.

In the event of occupational exposure, promptly rinse the wound, assess the infection risk, and, if necessary, initiate post-exposure prophylaxis (PEP) for HIV. It is also critical to report the incident within 24 hours and maintain long-term monitoring records.

By enhancing operational standards, technical measures, and management systems in a coordinated manner, the goal of "zero reuse, zero contact, zero exposure" in safe injection practices can be effectively achieved.