Injection needles come in various sizes and use. Different sized needles are used for different purposes. The type and size of injection needles used in treatment usually depend on the drug used. Sometimes, the size of the patient will also determine which size of injection needle to use.
It is crucial to choose the right size of needle and syringe so you get the correct dose of medicine, especially for people who need to inject themself with medication at home. Having the right size also makes the injection easier and less painful.
In general, your healthcare provider or a nurse will show you how to give yourself a shot at home, including which syringes and needles to use. It helps to be familiar with the basic principles of the injection needle and syringe sizing so you can avoid errors when it is time to replace them. This article explains injection needle sizing and provides some helpful tips for choosing the right size for the injection you need to give.
Injection Needle Size Guide
The specifications determine the injection needle diameter. As the diameter of the needle becomes smaller, the number of needles becomes larger. For example, a 24-gauge needle is much thinner than a 14-gauge needle. Doctors usually use the thinnest possible injection needle to avoid discomfort or pain for the patient.
The length of the injection needle is also significant. The type of syringe required for treatment will determine the size and length of the injection needle used. There are two main types of injection needles: intramuscular injection needles and subcutaneous injection needles.
IM Injection Needle Size
Intramuscular injections are administered at a 90-degree angle to the skin, preferably into the anterolateral aspect of the thigh or the deltoid muscle of the upper arm, depending on the patient's age. The needle gauge for intramuscular injection is 22-25 gauge with a length of 1 inch (2.54 cm) to 1.5 inches (3.81 cm). The vaccine is usually injected intramuscularly. Intramuscular injections generally require longer and thicker needles. The IM injection needle length and injection site must be made for each person based on the size of the muscle, the thickness of fatty tissue at the injection site, the volume of the material to be administered, etc.
Subcutaneous Injection Needle Size
Subcutaneous injection requires injecting the drug into the first layer of fat under the skin, injecting at a 45-degree angle into fatty tissue overlying the triceps muscle. Insulin injection is one example of subcutaneous injection. The subcutaneous injection needles are getting thinner and thinner. The usual size for subcutaneous injection needles is 25-30 gauge.
Injection Needle Size Chart
The needle packaging will have a label: number, a "G," and then another number. For example, a 22 G 1/2 needle has a gauge of 22 and a length of 0.5 inches.
- The first number in front of the letter G indicates the gauge of the needle. The higher this number is, the thinner the needle.
- The second number indicates the length of the needle in inches.
The gauges are based on the outer diameter. G or Ga means the needle number. The smaller the gauge, the larger the outer diameter. The inner diameter varies according to the size of the serial number and the thickness of the tube wall. The following table shows the nominal inner diameter and wall thickness of a conventional needle.
|Injection needle gauge||Outside diameter(inch)||Outside diameter(mm)||Inner diameter(inch)||Inner diameter(mm)||Thickness(inch)||Thickness(mm)|
|7||0.180"||4.57 mm||0.15"||3.81 mm||0.015"||0.381 mm|
|8||0.165"||4.20 mm||0.14"||3.43 mm||0.015"||0.381 mm|
|9||0.148"||3.76 mm||0.12"||3.00 mm||0.015"||0.381 mm|
|10||0.134"||3.40 mm||0.11"||2.69 mm||0.014"||0.356 mm|
|11||0.120"||3.05 mm||0.09"||2.39 mm||0.013"||0.330 mm|
|12||0.109"||2.77 mm||0.08"||2.16 mm||0.012"||0.305 mm|
|13||0.095"||2.41 mm||0.07"||1.80 mm||0.012"||0.305 mm|
|14||0.083"||2.11 mm||0.06"||1.60 mm||0.01"||0.254 mm|
|15||0.072"||1.83 mm||0.05"||1.38 mm||0.009"||0.229 mm|
|16||0.065"||1.65 mm||0.047"||1.19 mm||0.009"||0.229 mm|
|17||0.058"||1.47 mm||0.042"||1.07 mm||0.008"||0.203 mm|
|18||0.050"||1.27 mm||0.03"||0.84 mm||0.0085"||0.216 mm|
|19||0.042"||1.07 mm||0.027"||0.69 mm||0.0075"||0.191 mm|
|20||0.036"||0.91 mm||0.023"||0.60 mm||0.006"||0.1524 mm|
Common Needle Gauges
|Needle Gauge||Needle Length||Used for|
|18||1 Inch||Transferring intramuscular hormones from vial to syringe|
|21||1/2 Inch||Intramuscular injections (e.g., naloxone, steroids, hormones)|
|22||1/2 Inch||Intramuscular injections (e.g., hormones)|
|23||1 Inch||Intramuscular injections (e.g., naloxone, steroids, hormones), methadone|
|25||1 Inch||Intravenous drug use, intramuscular hormone administration, Intravenous crushed pills|
|27||1/2 Inch||Standard insulin set, intravenous drug use |
|28||1/2 Inch||Standard insulin set, intravenous drug use |
|29||1/2 Inch||Intravenous drug use|
|30||1/2 or 5/16 inch||Intravenous drug use|
|31||5/16 inch||Intravenous drug use|
Determining Injection Needle Size
If you need to inject yourself with a small amount of medication, using a thin, high-gauge needle will usually be less painful. For larger amounts of medicine, a wider needle with a lower gauge is often a better choice. While it might hurt more, a wide, low-gauge needle will deliver the drug faster.
Longer needles (½ inch or longer) are commonly used for intramuscular injections, while shorter (shorter than ½ inch) needles are often used for intravenous injections.
As far as the needle length, the best choice will depend on a person's size. For example, a small child would need a shorter needle than an adult. Where you are inserting the needle also matters. Some medications can be absorbed just under the skin. Others need to be injected into the muscle.
- Subcutaneous injections go into the fatty tissue just below the skin. The needle required is short, typically 1/2 to 5/8 inch long, with a gauge of 25 to 30.
- Intramuscular injections go directly into a muscle. Muscle is more profound than the skin, so the needle used for these treatments must be longer. Needles with a gauge of 20 or 22 G and a length of 1 or 1.5 inches are ideal choices.
You must also think about how much body fat the needle has to go through. A thin person might be able to use an inch-long needle. Someone heavier might need a needle that is an inch-and-a-half-long.