Some people with diabetes require insulin. They can manually administer this through several methods, such as syringes, which are available in different sizes with various-sized needles.

In the United States, more than 34 million people have diabetes. Of these, 7.4 million rely on insulin formulations to manage their blood glucose. Insulin is a hormone that helps to regulate blood sugar.

There are currently four main ways people can administer insulin: syringes, pens, pumps, and inhalers. How a person takes insulin can vary depending on their lifestyle, sugar levels, and what they eat.

Syringes deliver insulin through a needle and are available in different sizes to suit different doses, comfort levels, and costs.

In this article, we will discuss the different sizes of insulin needles and syringes.

A person using a syringe to administer insulin.Share on Pinterest
Carrie Yuan/Offset

Diabetes refers to a condition that impairs the body’s ability to process blood sugar. There are different types of diabetes, but all types result in irregular blood sugar levels due to the body not producing or using a hormone called insulin. This causes glucose to accumulate in the blood, which can cause health problems.

Insulin is a hormone the pancreas produces to help the body use glucose for energy. People with diabetes can manually use insulin to regulate their blood glucose levels and keep them within healthy ranges. There are many types of insulin, and they vary according to how quickly they can lower blood sugar and the length of time they can do this.

There are also many ways people can administer insulin. The method a person chooses may depend on their lifestyle, insurance, and preferences. A common method many people opt for is a needle and syringe, where they use the syringe to draw insulin from a vial or bottle.

Insulin syringes are available in multiple sizes to help deliver different doses of insulin. Most syringes come in measures of 30-units or 0.3 milliliters (ml), 50 units (0.5 ml), and 100 units (1 ml). These measures refer to the barrel size and how much insulin the syringe can hold. The barrels feature markings at 1- or 2-unit intervals to help people measure their dose.

The needle on the syringe is also available in different sizes, as they come in different lengths and gauges.

The length of the needle determines how deeply it penetrates. As they only need to go into the layer of fat and not muscle, the needles are not too long. They are typically available in sizes ranging from 4 millimeters (mm) to 12.7 mm.

The gauge of a needle refers to its thickness. Thinner needles may be more comfortable, while thicker needles may administer insulin quicker. The higher the gauge, the thinner the needle. They are typically available in sizes ranging from 28–31.

Regarding size, it is important that people choose a length and gauge they are comfortable with.

Evidence notes that a person’s size does not affect the efficacy or potential of insulin leakage when using shorter needles. Additionally, skin thickness is unlikely to vary much from person to person.

A 2020 study also highlights that people are more likely to prefer using shorter needles. In most cases, it may be advisable for people to use needles ranging from 4–8 mm in length.

People may also prefer thinner needles, as they are typically easier to use than thicker needles. A 2015 study notes that thinner needles are usually less painful and easier to insert.

While it is important for people to use a suitable size needle, it is essential that they use the correct technique to administer the insulin and appropriately rotate injection sites to ensure they manage their blood sugar and avoid potential complications.

Generally, it is advisable for a person to use as short and thin a needle as they are comfortable with.

If a person uses a needle that is too long, they may accidentally perform a painful intramuscular injection. As this will enter muscle rather than subcutaneous fat, the insulin will absorb much faster than it should, which could cause complications. Using a thicker needle than necessary will likely result in more painful injections.

A person’s diabetes care team should provide guidance on which types and how much insulin to use. They should also advise on the volume of insulin a person requires for their doses.

The barrel size will typically depend on the size of the dose a person requires, and they may need multiple sizes for different doses. It is advisable to choose a size that allows a person to administer their dose in one shot. For example, it may be easier to measure a 10-unit dose with a 30-unit syringe and a 55-unit dose with a 100-unit syringe.

As the body uses digestive enzymes to break down insulin, a person must use a subcutaneous injection to deliver the insulin into the layer of fat below the skin. The insulin can then absorb steadily into the bloodstream, where it circulates to cells throughout the body.

To draw insulin into a syringe, a person should:

  • Gather supplies: After first washing their hands, a person should get a fresh needle and the insulin vial. While checking they have the right kind of insulin, they can also check the insulin is in date and contains no particles. They may also need to gently mix the insulin.
  • Prepare the vial: A person can now take the protective covering off the insulin vial and sterilize the top with an alcohol swab.
  • Prepare the syringe: They can remove the cap from the needle and pull the plunger back equal to the dose the person requires. Put the needle through the rubber top of the vial and push the plunger to inject the air. Leaving the needle in the vial, turn both the bottle and syringe upside down. Pull the plunger to withdraw the desired dose.
  • Checking the syringe: Before removing the needle, a person should check the syringe for bubbles. If bubbles are present, tap the side of the syringe until the bubbles float to the top. Then push the bubbles out using the plunger and draw back in until the syringe has the correct dose.
  • Removing the needle: A person can now safely remove the needle from the vial. They should make sure the needle does not touch anything until they inject.

An individual is now ready to inject the insulin. Common injection sites can include the stomach, hips, thighs, buttocks, and backs of the arms. To administer the insulin, a person should:

  • Select a site: Choose which area to inject the insulin. Ideally, it should be different from the previous injection site, so a person does not overuse a particular area of skin. After deciding, a person should then clean the area with an alcohol wipe.
  • Pinch the skin: Now that the area is clean, a person will need to pinch the skin and fatty tissue between their thumb and first finger.
  • Insert the needle: With one quick motion, a person can now insert the needle into the pinched skin. When the needle is inserted, the person can relax and release the skin.
  • Inject the insulin: Now that the needle is in place, a person can slowly push down on the plunger to inject the dose of insulin. After administering the dose, a person should leave the needle in the skin for five seconds.
  • Removing the needle: A person can now pull the needle straight out and apply gentle pressure over the injection site to prevent any insulin from leaking out. Do not rub the site.
  • Disposing of the syringe: Now that a person has used the syringe, they can place the syringe in a safe place, such as a sharps container. They can then dispose of the medical waste according to the standards of the local department of sanitation.

Click here to learn more about using an insulin pen.

For people with diabetes, injecting insulin is essential for maintaining their health. Using a needle and syringe is a common and cost-effective way for many people to take their insulin.

For those who regularly inject insulin, the syringe and needle size can make a big difference in managing their comfort and blood glucose levels. If people have any concerns about needle size and technique, they can discuss this with their diabetes care team.