Definition
The insulin syringe is basically not different from other kinds of syringes. It has the same essential parts as the others, but it is designed with a slimmer barrel and smaller needle.
Its task is to deliver insulin into the patient or recipient’s subcutaneous (immediately below the skin) tissue. Since the amount of insulin injected is not that big, the syringe is designed to have a narrower and slimmer barrel. Since the injection area is subcutaneous, the needle is intended to be smaller, shorter, and finer than others.
Prevention of pain is of paramount importance and consideration in developing insulin syringes. In most cases, the patients themselves do the injections, and the injections are done daily.
Parts
There are two kinds of insulin syringes: (1) insulin syringes with fixed needles, and (2) insulin syringes with the detachable needle or without the needle.
Insulin syringes with fixed needles
The syringe with a fixed needle is available in sizes of 0.3, 0.5, 1.0 ml.
Both types of syringes consist of the following parts: needle cap, needle, gasket, barrel, and plunger. The only difference is that the syringe with a fixed needle has a plunger cap. In contrast, the syringe with a detachable needle has none.
The barrel is a tube-like and cylindrical structure that holds the insulin before the injection. Upon the side of the barrel, the markings in terms of International Units are printed. In most, the insulin syringes are provided with 100-unit barrels. In terms of insulin concentration, most of the time, insulin is supplied in U-100, which means that 100 units of insulin are contained in one milliliter of fluid.
The sizes of the barrel are expressed in terms of a milliliter. Every size is intended for a particular amount of insulin to be injected. Below are the dimensions and corresponding uses:
· 0.3 mL syringes are for insulin doses below 30 units of insulin and are numbered at 1-unit intervals.
· 0.5 mL syringes are used for 30 to 50 units of insulin and are numbered at 1-unit intervals.
· 1.0 mL are used for doses of more than 50 units of insulin and are numbered at 2 units per interval.
Insulin syringes with the detachable needle or without the needle.
In comparison, the syringe with the detachable needle or no needle is available in sizes of 0.5 and 1.0 ml.
The plunger is the rod that is inside the barrel. It can be pushed down or pulled up depending on the purpose of using the syringe. If the rod is pushed down, then the content of the barrel will go out. If the rod is pulled up, then a fluid could be aspirated or sucked inside the barrel.
It fits very tightly and snugly in the barrel, and it has a rubber tip known as a gasket on one end and a plastic disc on the other. Pushing the disc on the plunger will cause the rubber tip to push the insulin out of the barrel and through the needle. In the syringe with a fixed needle, the plunger is protected by a cap.
The last essential part of the insulin syringe is the needle. It is finer, thinner, and shorter compared to the needles used for other purposes. This design reduces the trauma the patient or recipient will experience when the injection is done daily.
In addition, being finer and thinner, the patient will experience minimal pain as the needle finds its way into the subcutaneous tissue. Finally, the needle is covered and protected by a cap when not used in both kinds of syringes.
Size chart for common insulin syringes
| Needle length | Needle gauge | Barrel size |
| 3/16 inch (5 mm) | 28 | 0.3 ml |
| 5/16 inch (8 mm) | 29,30 | 0.5 ml |
| ½ inch (12.7 mm) | 31 | 1.0 ml |
Bases of selecting insulin syringe to use
· You need to consider the amount of insulin that you need to inject and your comfort level to a particular size of the needle; based on these, select the most appropriate syringe size as presented in the preceding;
· Select the correct syringe so that you can give yourself the right amount of insulin in one shot. If you selected the wrong syringe, either you need to give yourself another shot to complete your daily dose, or you erroneously gave yourself a higher amount of insulin;
· If you have several insulin doses in a day, you may need several sizes of syringes. For example, if you need 35 units of insulin in the morning and 10 units in the evening, then you will use a 0.5 ml syringe in the morning and 0.3 ml syringe in the evening;
· The different sizes of insulin syringes allow you to choose what size to use when your physician is still calibrating the amount of insulin you need. If there are changes in your sugar level in a day, you may need to change your syringe(s) accordingly.
· If your dose is close to the maximum capacity of the syringe you are currently using, you need to replace your syringe with the next bigger size to avoid handling problems.
Sites of injecting the insulin syringe
· The insulin is injected subcutaneously—that is, in the fat layer immediately below the skin. For this reason, the correct length of the needle should be used—short enough to reach the fatty tissue. If too long, you might hit the muscle, and your insulin is absorbed too quickly, and you will experience an immediate lowering of your blood sugar;
· If you are injected with insulin daily, you need to rotate the site of injection. If you use the same spot all the time, you may develop lipodystrophy wherein fat breaks down or builds up under your skin, causing lumps or indentations which will soon interfere with the absorption of insulin;
· The rotation of injection can be done in several ways. If you are injecting on your abdomen, you can rotate the injection site by injecting in an area one inch away from the previous site. Another way is to migrate to another body site such as your thigh, arm, or buttocks.
Precautions in using insulin syringes
· Disposable syringes must never be used more than once;
· If you plan to re-use your insulin syringe, ask permission from your attending physician. However, as a general rule, the following patients or individuals are not allowed to re-use their insulin syringes:
(1) having trouble seeing clearly,
(2) difficulty in using the hands, and
(3) open wounds with or without infection;
· When putting back the cover of the needle, we should place both the cover and the syringe on a flat surface and then slide the cover over the needle. Ensure that the needle does not touch the flat surface or any of your fingers. Only the inside of the cover should touch the needle.
· Do not clean the needle with alcohol. It removes the silicone covering on the needle, causing it to become dull.
· Store the syringes at room temperature. If the syringe still contains insulin, store the covered needle in the syringe pointing up to prevent insulin from blocking the needle opening.
