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Insulin Syringes: Proper Use and Care

Nov 20, 2023
Insulin Syringes: Proper Use and Care

Giving yourself an injection at home is easy once you gain confidence in how to read your medication dose and correlate it to the marks on an insulin syringe.

Whether you were prescribed an injectable nutrition supplement (e.g., amino blends), erectile dysfunction treatments like Trimix, GLP-1s for weight loss, or Sermorelin, understanding how to properly self-inject these medications is essential.

As telehealth has expanded healthcare options, more medications are available for self-injection. This market continues to grow. In 2021, the self-injectable market size was $6.6 billion. It is estimated to grow by about 6% each year from 2022 to 2030.

Barrel, Needle, and Plunger

Self-injection devices, including insulin syringes and auto-injectors, have three parts:

  • Barrel: This is a clear plastic tube that contains the medication and has measurement markings down the barrel. The barrel is typically marked at 1- to 2-International Unit intervals to help you measure your medication dose. Syringes also vary in size to accommodate different medication volumes.
  • Needle: Needles vary in length and gauge and are covered by a protective cap. The length is crucial for determining the depth of penetration. This is important for ensuring the medication is delivered to the correct tissue (subcutaneous or muscular). The gauge determines how quickly the medication is injected.
  • Plunger: This is the plastic handle at the top of the syringe. In fixed needle insulin syringes, it is covered by a plunger cap. Pulling on the plunger allows you to bring air or medication into a syringe, and depressing the plunger forces the medication or air out of the syringe. The plunger fits snugly in the barrel. It has a rubber tip known as a gasket on one end and a plastic disc on the other end.
Insulin syringes

Types of Insulin Syringes

Insulin syringes vary by size. It is important to match your syringe size to your dose.

If you have a syringe that is too large, the measurement intervals will be too large, and you cannot get an accurate dosage measurement. If the syringe is too small, it will not hold your whole medication dose.

Insulin syringes may come with fixed needles or a detachable needle. Disposable fixed-needle insulin syringes are designed for single use.

Size of the Syringe

The size of the syringe depends on the amount of medication it can hold. The three sizes of insulin syringes are:

  • 0.3 milliliter (mL) (30 units): numbered at 1-unit intervals
  • 0.5 mL (50 units): numbered at 1-unit intervals
  • 1 mL (100 units): numbered at 2-unit intervals

Syringes with detachable needles are available in 0.5 and 1.0mL sizes.

Converting Milliliters (mLs) to Units

There are 100 units in a milliliter (ml).

  • 1 mL contains 100 units
  • 0.5 mL contains 50 units (0.5 mL is half of 1 mL)
  • 0.1 mL contains 10 units
  • 0.01 ml contains 1 unit
Insulin syringe

Needle Sizes and Diameters

The needle on a syringe is also available in assorted sizes. They vary in length and gauge.

Needle Length

The length of a needle determines how deeply it penetrates. Suppose your medication is to be injected subcutaneously (just under the skin). In that case, you will not need as long a needle as you need to inject your medication into your muscle. Needle length is measured in millimeters (mm) or inches. It can vary from 5 mm to 12.7 mm and from 3/16 inch to 5/8 inch for subcutaneous injections.

Needle Gauge

The gauge of a needle refers to its thickness. The higher the gauge, the thinner the needle. Thinner needles may be more comfortable, but they administer your medication more slowly. The gauge of a needle varies from 25 to 31.

Recommended needle size depends on the viscosity (thickness) of your medication, the depth of the injection, injection location, body size, and personal comfort.

Longer needles may be easier for some people to manage, but typically, shorter needles are preferred for subcutaneous injections to help ensure the medication dose is delivered into the fatty tissue just under the skin and not muscle tissue.

Questions: Ask your doctor

Questions About Medication Dosage or Injection

Your healthcare provider should make available all the equipment you need to inject your medication. Contact an Invigor Medical treatment specialist if you have questions about your dosage or proper injection technique.

While we strive to always provide accurate, current, and safe advice in all of our articles and guides, it’s important to stress that they are no substitute for medical advice from a doctor or healthcare provider. You should always consult a practicing professional who can diagnose your specific case. The content we’ve included in this guide is merely meant to be informational and does not constitute medical advice.

Insulin Syringes: Proper Use and Care

Leann Poston, M.D.

Dr. Leann Poston is a licensed physician in the state of Ohio who holds an M.B.A. and an M. Ed. She is a full-time medical communications writer and educator who writes and researches for Invigor Medical. Dr. Poston lives in the Midwest with her family. She enjoys traveling and hiking. She is an avid technology aficionado and loves trying new things.


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