How to Read Insulin Syringes & Get the Right Dose?

Insulin syringes have unique unit measurements that are specific to insulin dosages. Therefore, learning how to read and use insulin syringes accurately is absolutely crucial for good diabetes management. So, here’s our comprehensive guide!
 
Related article: How to Store Your Insulin Correctly?

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Different Types of Insulin Syringes

Insulin syringes, sometimes called "diabetic syringes," come in different sizes and types to meet individual needs. They may differ in size, needle length, gauge, and unit measurement:

U-100 and U-40 syringes

There are two main types of insulin syringes: U-100 and U-40. It's all about the concentration of the insulin you're using, and it greatly matters!
 
You absolutely must use a U-100 syringe with U-100 insulin and a U-40 syringe with U-40 insulin. Using the wrong syringe type can result in incorrect dosing, which can lead to hyperglycemia (high blood sugar) or hypoglycemia (low blood sugar).
 
Fortunately, nowadays, most human insulins sold in the U.S. are U-100, so there is little room for confusion. Still, always make sure to double-check check your syringe matches the concentration of your insulin before using it for injection.

Related article: Can you Prefill Insulin Syringes & How Long Are They Good for?

Syringe sizes

The size of an insulin syringe refers to its maximum capacity in milliliters. Typically, U-100 insulin syringe sizes range from 0.3 ml to 1 ml. 0.3 ml syringes can draw 0.3 ml of insulin, 0.5 ml syringes can draw 0.5 ml, etcetera.
 
Because a U-100 insulin contains 100 units of insulin per milliliter of fluid:

• A 0.3 ml syringe can hold up to 30 units of insulin.
• A 0.5 ml syringe can hold up to 50 units of insulin.
• A 1 ml syringe can hold up to 100 units of insulin.

Therefore, 0.3 ml syringes are designed to be used for insulin doses under 30 units, while 0.5 ml syringes are for 30 to 50 units and 1 ml syringes for higher doses up to 100 units.
 
Related article: How to Convert Insulin Units to mL?

Needle gauge and length

Insulin syringes may come in different needle sizes too. The gauge is the thickness of the needle. Insulin syringes typically have a gauge between 27 and 31, with a higher gauge indicating a thinner needle. Needle lengths usually range from 4 mm to 12.7 mm.
 
Ask for your doctor’s advice on what needle gauge and length are best for you. Besides comfort during the injection, several individual factors must be considered, including the type of insulin you're using and the thickness of your subcutaneous tissue.
 
Related article: The Ultimate Guide to Insulin Pen Needle Sizes!

The different parts of an insulin syringe

Before learning how to read an insulin syringe, it's helpful to be familiar with its different parts:

• The needle.
• The barrel is the part that holds the insulin. It is marked with measurements to indicate the amount of insulin being drawn into or expelled from the syringe.
• The plunger is the movable part used to draw insulin into the barrel and inject it.
• The cap is the removable protective cover that protects the needle to prevent contamination and accidental needle sticks.

Some insulin syringes may also have additional features, such as a safety shield, a protective mechanism, or a detachable needle that can be replaced after each use.  
 
Related article: 10 Tips That Work to Inject Insulin Without Pain!

How to Read Insulin Syringes (U-100)

Insulin syringes look similar to regular syringes but are numbered in units. As you know, insulin is measured in units, not mL, unlike most other injectable medications. 
 
Therefore, the numbers on an insulin syringe indicate the number of insulin units being drawn.
 
For U-100 insulin syringes, each line on the syringe barrel represents one unit of insulin. Depending on the syringe size, it may have markings up to 100 units. For example, a 1 ml U-100 insulin syringe will have markings up to 100 units, while a 0.5 ml U-100 insulin syringe will have markings up to 50.
 
When drawing insulin into a syringe, always read from the top ring (the needle side). Once you have identified the increments on the syringe barrel, you can measure the amount of insulin by counting the number of lines from the needle end to the desired amount of insulin. For example, if you need to measure 20 units with a U-100 insulin syringe, you will draw the plunger to the line marked "20" on the syringe barrel.
 
Related article: How to Calculate Your Insulin Dose Correctly?

How to inject insulin with a syringe?

Unlike prefilled insulin injector pens, using insulin syringes requires drawing the insulin dose from a vial into the syringe to prepare your subcutaneous injection. 
 
This gesture may seem daunting at first, but it will quickly become second nature with practice. It’s quite simple, but it must be done correctly to ensure you receive your full insulin dose. Here are the steps to follow:

1. Wash your hands.
2. Gather your injection supplies (insulin vial, syringe, alcohol swabs, and sharps container).
3. Prepare the injection site.
4. Prepare the syringe: Remove the needle cap and pull back the plunger to draw air into the syringe equal to the amount of insulin you need to inject.
5. Inject the air into the vial.
6. Draw your dose of insulin.
7. Inject the insulin: Hold the syringe like a pencil and insert the needle into the skin at a 90-degree angle. Push the plunger down slowly to inject the insulin. Wait for 10 seconds.
8. Remove the needle.
9. Dispose of the syringe in a sharps container. 

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What about you? Are you using insulin syringes or pens? Do you find them difficult to read or use?