Insulin is a life-saving medication that helps millions of Americans with Type 1 and Type 2 Diabetes control their blood sugar levels every single day. It can be delivered in a variety of different ways, but the most common delivery method is via subcutaneous injection.

Whether you’re new to injecting insulin or are looking for a refresher, understanding the fundamentals of insulin syringes is essential. Below, we’ve provided an overview of the purpose and components of insulin syringes and information on how to read and properly select them.

Though well-researched, the information in this article is not a replacement for medical advice. For questions about how to inject insulin based on your specific medical needs, it’s vital to make an appointment with your healthcare provider.

The Purpose of Insulin Syringes

The purpose of an insulin syringe is to help you effectively inject insulin into the fatty layer under your skin.

If you are living with Diabetes, your pancreas may not be producing enough insulin (Type 1 Diabetes) and/or your body may not be using insulin efficiently (Type 2 Diabetes). Subcutaneous insulin injections can help you maintain healthy blood sugar levels by allowing your body cells to metabolize glucose from your bloodstream effectively.

Anatomy of an Insulin Syringe

Every insulin syringe is made up of 3 main components plus a cap. Let’s take a closer look:

  • Barrel – The barrel is the round, tubular part of the syringe that holds the insulin prior to injection. It is marked with measurement lines to indicate the volume of medication that has been drawn.
  • Plunger – The plunger sits inside the barrel. It moves up and down to draw in insulin and push it back out.
  • Needle – The needle is situated at the tip of the barrel and is the component of the syringe that is injected under the skin for insulin delivery. When the plunger is deployed, medication flows out the tip of the needle.
  • Cap – A cap keeps the needle protected before use and should be replaced after usage before disposal.

Types of Insulin Syringes

There are various types of disposable insulin syringes available to patients. While they all have the same components and function similarly, there are 3 variables that can distinguish them from one another. These are:

  • Syringe Size – This refers to the volume of insulin the barrel can hold. Common syringe sizes include 0.3 mL, 0.5 mL, and 1.0 mL.
  • Needle Gauge – This refers to the thickness of the needle. The higher the needle gauge, the thinner the needle.
  • Needle Length – This refers to how long the needle is and how far it will penetrate under your skin. Shorter needles are typically preferable for subcutaneous injections because they reduce the risk of accidentally injecting insulin into a muscle.

How To Read Insulin Syringes

Reading your insulin syringe accurately is critical to your health and well-being. While not complicated, there are a few pieces of information that are important to be aware of.

Insulin is typically dosed in units, which are related to mLs as follows:

1 mL = 100 units

In other words, each unit of insulin is equal to 0.01 mL.

This means that a 0.3 mL syringe can hold 30 units of insulin, a 0.5 mL syringe 50 units, and a 1.0 mL syringe 100 units.

Often, the finest gradation lines on an insulin syringe represent single units, but it is always important to confirm this before measuring your dose of insulin into the barrel.

Calculating Your Dosage

In general, your healthcare provider or pharmacist will provide a dosage calculation for you. If you need to calculate dosage amounts on your own, it’s completely doable. It simply requires a little math. Let’s walk through the process:

Your insulin dosage will typically be provided in mg, and your vial will typically show insulin strength in mg/mL.

Let’s say you’ve been prescribed a 100 mg dose of insulin, and your vial contains insulin at a concentration of 200 mg/mL.

You’ll need to convert your mg dosage into mL.

In this example, you’ll calculate that if 1 mL contains 200 mg, then 0.5 mL will contain 100 mg (which is your dosage).

Next, you’ll apply the knowledge that 0.5 mL is the same as 50 units of insulin and draw the proper amount into your syringe accordingly.

Speak directly with your healthcare provider for more specifics about calculating your insulin dose(s).

How To Choose the Right Size Insulin Syringe

Selecting the proper syringe for your insulin injections will increase your comfort and ability to accurately administer the proper dose of medication every single time. In general, your healthcare provider will recommend an insulin syringe size for you. That being said, knowing how to select the best syringe for your needs is highly recommended.

Here are some helpful tips:

  • Choose the smallest syringe that can hold your full dose of insulin. Using multiple syringes for a single dose of medication is uncomfortable and can result in errors.
  • If your treatment plan involves taking different doses of insulin at different times, you may require more than one size of insulin syringe.
  • If your doses are approaching the maximum capacity of your syringe, you may find the next size up easier to handle and administer.
  • Many patients prefer the thinnest, shortest needles possible to maximize comfort. Speak with your healthcare provider to determine which needle number and length will be best for your needs and circumstances.


To conclude, insulin syringes are a means of injecting life-saving medication. They’re not hard to use, but understanding how they work and how to read them properly is critical.

In this article, we’ve covered the basic components of insulin syringes, explored how to calculate and draw a proper dose of medication, and provided some tips on selecting the right syringe for your particular needs.

Many Americans can’t live healthy lives without insulin, but its price can be overwhelming. Are you looking to source high-quality insulin at an affordable price? can help. For more information or to place your order, contact us directly today!

See also: Humulin vs Humalog

About the Author

Ida Edlweiss Gumpal is a licensed Pharmacist and medical writer. She took her internships at Mercury Drug Corporation, Inc., a Hospital internship at De Vera Medical Center, Inc., and a Manufacturing internship at Philmed Laboratories, Inc. She has plans on attending medical school with the goal of specializing in Neurosurgery or Cardiothoracic surgery.