The average person doesn’t spend a whole lot of time thinking about syringes or needles. We encounter them when we get a vaccine or must get blood drawn but beyond that, the layperson couldn’t tell one needle or syringe type from the other. For those in the medical community or someone living with a chronic medical condition, needles and syringes, along with all of their many variations in sizes and types, becomes very important. There are many types of syringes all serving a different purpose and as many types and sizes of needles each having their own purpose as well. Knowing what kind of syringe or needle you need can be confusing. At Medlab Gear we’ve devised this ultimate guide to selecting syringes and needles to help make the process easier for you. While this guide should be useful when shopping for syringes and needles, remember to always follow the direction and advice of your prescribing doctor for administering medications.
Types of Syringes and Needles
It’s important to note that there are a variety of syringe types and needle sizes. Some syringes are used alone without a needle and others are used in conjunction with a needle to administer injections. If you are a parent, you might be most familiar with a dosing syringe used to measure your child’s medication such as a pain reliever or antibiotic. This would be a type of syringe used without a needle. The syringe enables accurate measuring of the liquid and an easier way to get a young child to swallow the oral medication than a medicine cup or pill.
Another common syringe used without a needle is one for irrigation that can be used alone or with medical tubing. Some syringes come with the needle attached and filled with pre-measured medication. In this case, you don’t need to know too much about the size or type. Other times you must choose the size syringe you need based on the volume of liquid you need it to administer and, in this case, you’d choose the needle to go with it. Needles come in various lengths and diameter and are measured in gauges. You select the gauge based on where the injection is going and what type of medication is being injected.
Dissecting the Syringe
There are several parts and pieces that make up a syringe. We’ll start with the tip. The tip of the syringe can come in many types and shapes:
- Catheter tip. The tip on this syringe is long and tapered at the end. Most often this type of syringe will be selected for use with tubing or for irrigation. The tubing slips over the tip of the syringe.
- Slip tip. The tip on this type of syringe is usually in the center of the syringe and is shorter in length. Much like the catheter tip, it pushes onto tubing or a needle.
- Eccentric tip. This tip is located off-center on the syringe. It is used most often with a needle that needs to penetrate the skin or vein superficially at a horizontal angle to the skin.
- Luer Lok tip. This tip is the most commonly used. This tip small and centered and allows the needle to quickly and securely attach in a screw-like fashion.
The next piece of the syringe is the barrel which is the main body of the syringe. On the barrel, there are volume markings that allow you to measure the exact amount of liquid required in the syringe. The size of a syringe barrel can vary from a small slender barrel to one as large around as a quarter. The size barrel you select is dependent on the volume of liquid you need to administer and the flow rate needed for the injection. In general, the smaller the syringe the faster the flow rate and the larger the syringe the slower the flow. Usually smaller size syringes are used for injections such as immunizations. Mid-sized syringes are used for tubing or catheters. The largest size barrels are usually used for irrigation. Syringes are measured in cc or mL volumes, the smaller number being the smaller size syringe.
At the base of the barrel of the syringe is the flange. The flange is the area that gives you something to hold on to. Most commonly a person administering fluid or medication through a syringe will position it with their pointer and middle fingers on either side of the barrel resting on the flange.
The plunger is the final piece of a syringe. The plunger is what pushes into the barrel of the syringe to force the liquid out of the tip. There is a plunger tip usually made of some type of rubber that forms a seal preventing the liquid from leaking out of the syringe. A person usually uses their thumb to push the plunger base into the syringe.
Examining the Needle
At first thought, it may seem like a needle is a needle, a pointy thing that jabs into you! However, needles come in varying lengths and widths and each serves a different purpose. Who knew there could be so many different needles and measurements to concern yourself with?!
Needles are measured in gauges. To make things confusing, needle sizes are the reverse of syringes. The smaller the gauge the larger the needle, the larger the gauge the smaller the needle. Larger gauge needles, being the smallest, are usually the least painful and leave less bruising at the injection site. Smaller gauge needles are larger and therefore sturdier and less likely to break.
The type of injection you need to do usually determines the size needle you choose. There are several types of injections, including:
- Intradermal Injection. This type of injection is relatively superficial and only punctures the outer layers of skin. A shorter length needle ranging from 3/8 to ¾ inches and a higher gauge around 26 to 28 are usually selected for intradermal injections. The angle for this type of injection is about 10 to 15 degrees so that it is inserted only into the upper layers of dermis or epidermis.
- Intramuscular Injection. This injection goes the deepest into the muscle. Needles for this injection can be about an inch to two inches long and are usually injected at a 90-degree angle to the skin. Surprisingly, the gauge for intramuscular injections is large making the needle some of the thinnest used, ranging in size from about 26 to 30 gauge.
- Subcutaneous Injection. This is the middle of the road injection, past the dermis and epidermis but not as deep as muscle. Ideally, this needle enters the subcutaneous tissue at a 45 to 90-degree angle. Needle length is usually small for these injections, so they don’t puncture too deeply, ranging from ½ to 5/8 inch. Gauge size can range the most for this type of injection from 27 to 19, some of the larger needles.
In addition to all of this, the viscosity of the fluid being injected also influences the needle selection. The higher the viscosity, the thicker the fluid and the larger smaller gauge needle is needed. If the viscosity is low, like water, then a thinner higher gauge needle can be used.
There are also several parts of a needle. The hub is at the base and should match the type of syringe selected whether screw on or slip on. The shaft of the needle is the actual needle itself. At the tip, you have the bevel which is the tip that pierces the skin and the lumen which is the diameter of the hollowed-out part of the needle.
Selecting the Right Needle and Syringe to Buy
Even with all that information, how do you know if you are selecting the right syringe and needle for the liquid that you need to inject? Before purchasing needles and syringes ask yourself these questions:
- Where do you need to inject the medication? The thigh, arm, buttocks, on the surface of the skin or into the muscle?
- What is the viscosity of the medication you need to inject? Is it fluid like saline or thick like honey?
- How much medication do you need to inject or how much fluid do you need to flush out? A small amount means a smaller syringe while large amounts mean a thicker, bigger syringe.
- Does the type of syringe tip match the needle hub you are selecting?
At Medlab Gear we have all the medical supplies you need. You can read descriptions of each syringe and needle to help you make the right decision. We are a trusted provider of top-quality medical supplies and products that will be discreetly delivered right to your door. Our team of medical supply experts is available to help you answer your questions should you have any trouble selecting the products that are right for you. Shopping for your syringes and needles from the comfort of your home is easy with our extensive guide and a wide selection of products.
I am a UK based doctor with over 8 years experience in both Medicine and Surgery alongside a background in medical education, teaching from school level up to postgraduate level. I provide medical consultancy to various online services internationally, of which two I am co-founder.
From 2008 to 2010 I created a dual curriculum for a private sixth form college, aimed at 16 to 18 year olds. This included a range of subjects and training for the university application process. In recent years I have continued to assist both UK and US students in their medical school applications alongside my usual clinical work.
My professional development as a doctor includes various audits, presentations up to regional level and research alongside CPD study days. I am currently completing my Diplomate of the Faculty of Reproductive and Sexual Health.
I also teach medical students and healthcare professionals such as doctors, nurses and physiotherapists either during bedside teaching on the ward or at more formal lunchtime seminars.
Why I love to write:
From my time as a teacher at pre-University level and working as a doctor I have accrued many hours of teaching aimed at a variety of levels of understanding. Most importantly, I have over 5 years experience in translating complex medical jargon into easy to understand information for patients and their relatives throughout a number of differing specialties.
Cardiff Medical School 2006 – 2011 MB ChB
Teacher at Cardiff Sixth Form College (2008 -2011)
Hospital Doctor / Senior House Officer for the NHS in multiple hospitals around England and Wales, UK. (2011 – present)