All About Insulin Needles and Syringes

People with diabetes either don’t produce the hormone insulin or don’t produce the right amount to regulate glucose (sugar) in the bloodstream. People with type 1 diabetes and many with type 2 therefore have to administer insulin. Insulin is typically taken two or more times a day.

Insulin can be human insulin, which is a synthetic version of the insulin made in the body, or an insulin analog, which is also lab-made but is genetically altered to affect how quickly it acts in the body. Human insulin does not require a prescription, while insulin analogs do.

Insulin can be delivered in several different ways—via a pump, a patch, an inhaler, a pen, a syringe, or a port. The most common delivery method is a syringe containing a needle, which allows the individual to self-inject the insulin directly under the skin.

Using the right insulin needles and syringes is important both for effectiveness and for comfort.

A syringe is a small pump that contains a barrel, a plunger, and the needle that pierces the skin.

The syringe is used to pull the insulin out of a vial and into the barrel, which is marked with dosing measurements. The user inserts the needle under the skin, typically in the abdomen, and then pushes the plunger to inject the insulin directly into the top layer of fat.

Syringes are disposable and intended to be used only once. Reusing or sharing needles and syringes can introduce bacteria or other pathogens and cause infection.

Talk to your doctor about the correct syringe size for you depending on your dosage of insulin. The size of your syringe may need to be adjusted as needed with your prescription.

The needle that delivers the insulin is very thin and designed for one-time use. Needles should always be injected directly into the skin (not through clothing) at a 90-degree angle to minimize insulin leakage.

The needle should reach the fatty layer between the skin and muscle (subcutaneous fat).

How and Where to Inject Insulin

Anyone using insulin should rotate the injection sites on the body part, preferably in the abdomen for maximum effectiveness. Some people choose to use the upper arm, thigh, or buttocks. Repeating injections in the same spot could lead to lipohypertrophy, or fatty nodules under the skin.

The American Diabetes Association has a guide to injection products which can help with pain management or also be useful for people with a fear of needles, dexterity challenges, or vision impairments.

Syringes come in at least three different sizes for varying amounts of insulin prescribed by a doctor:

• 0.3 milliliter syringes are appropriate for use with less than 30 units of insulin

• 0.5 milliliter syringes are used for 30 to 50 units of insulin

• 1.0 milliliter syringes are used for more than 50 units of insulin

Which Size Insulin Syringe to Use

The correct size of the syringe will depend on the amount of insulin prescribed. The barrel size determines how much insulin the syringe can hold.

A good rule of thumb is to use the smallest syringe that can contain your largest dose, which will help avoid user error.

Needles are measured by their length and gauge, or thickness. Doctors generally recommend using needles with a length of 4 millimeters to 6 millimeters.

There is no reason to use a needle longer than 8 millimeters, for nearly all body types. Longer needles can pierce too deep, delivering an intramuscular injection. Injecting insulin into the muscle can increase absorption, potentially leading to hypoglycemia (dangerously low blood sugar).

In the past, many thought that the size of the needle should be adjusted for a person’s weight, meaning people with obesity required longer needles. While certain people with obesity and other conditions like arthritis may benefit from a longer needle, more recent studies have shown that body weight overall is not a factor in needle size effectiveness, according to a review article published in 2015 in Diabetes Spectrum.

Regardless of body mass index (BMI), a 4-millimeter needle has been shown to be effective in nearly all individuals with diabetes, according to the article.

While shorter needles are now the standard of care, doctors should keep in mind the needs of individual cases.

Insulin needles can be purchased online or at pharmacies and stores including Walmart, Walgreens, and CVS. In some cases, the products are located behind the counter in the pharmacy area.

The American Pharmacists Association has long supported over-the-counter sales of needles and syringes to help prevent the transmission of blood-borne diseases.