For people with diabetes who inject insulin, the syringe and needle size can make a big difference in comfort and staying on track with steady blood sugar levels.

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More than 34 million people have diabetes in the United States.

In type 1 diabetes, the body can’t make its own insulin to regulate blood sugar levels. In type 2 diabetes, the body can’t use insulin efficiently or make enough.

Nearly 7.4 million people with diabetes in the United States need to take insulin to manage their blood sugars.

Insulin can be given in different ways: syringe, pen, pump. Your doctor will help you decide which type is best for you depending on your insulin dose, comfort level, and cost factors.

Whether you’re new to giving yourself insulin injections or it’s a daily routine, there are several points to consider including the syringe and needle size to maintain steady blood sugar levels.

In this article, we’ll go over the important points about insulin syringes you need to know.

There are a few things to keep in mind when buying insulin syringes.

Insulin syringes are disposable and meant for one-time use. This helps make sure the needles are sterile to avoid the risk of infections from used needles.

It’s also important to rotate injection sites to avoid lipohypertrophy, or an abnormal fat deposit under the skin. It’s a common complication with daily insulin injections.

Insulin is given as a subcutaneous injection — or just under the skin — so the needle doesn’t go into muscle, which could affect your blood sugar levels.

The best syringe size for you depends on your insulin dose. Since your insulin dose may change, going up or down depending on your blood sugar levels, you may need multiple syringe sizes to adjust your dose as needed.

Insulin needles themselves also come in multiple sizes and thicknesses.

Insulin syringes come in multiple sizes to deliver different doses of insulin.

The number lines in an insulin syringe, measured in milliliters (mL), stand for the following:

  • 0.3 mL syringes are for insulin doses under 30 units of insulin and are numbered at 1/2-unit or 1-unit intervals.
  • 0.5 mL syringes are for 30 to 50 units of insulin and are numbered at 1-unit intervals.
  • 1.0 mL are for doses more than 50 units of insulin and are numbered at 2 units per interval.

The size of the barrel determines how much insulin a syringe holds, and the needle gauge determines the needle thickness. Thinner needles may be more comfortable to inject for some people.

The length of a needle determines how far into your skin it penetrates. Needles for insulin only need to go just under your skin and not into muscle. Shorter needles are safer to avoid going into the muscle.

Size chart for common insulin syringes

Barrel size (syringe fluid volume)Insulin unitsNeedle lengthNeedle gauge
0.3 mL< 30 units of insulin3/16 inch (5 mm)28
0.5 mL30 to 50 units of insulin5/16 inch (8 mm)29, 30
1.0 mL> 50 units of insulin1/2 inch (12.7 mm)31

Insulin syringes come in multiple sizes with different needle length options.

The correct size depends on your insulin dose and your comfort level with the needle size. It’s important to choose the correct size to give yourself the full dose of insulin in one shot and to avoid errors in dosing from using the wrong syringe.

You may need multiple syringes if you give different doses per day. For example, 35 units in the morning and 10 units at night means you need a 0.3-mL syringe and a 0.5-mL syringe for each dose.

Syringes also allow more flexibility if doses need to be adjusted daily based on your blood sugar levels.

If your dose is close to the maximum capacity of the syringe, you may want to go up a size to avoid problems handling the syringe.

Studies on insulin needle size have shown that body mass index (BMI) doesn’t matter when it comes to the length of the needle to get an accurate insulin dose. BMI is one way to estimate body fat based on height and weight.

Needles as short as 4 millimeters (mm) have shown to provide accurate dosing. This may be important for your comfort with giving yourself insulin injections every day if you don’t like big needles.

Thinner gauge needles may also be less painful, so if you need daily injections, this is something for you to consider and discuss with your doctor.

Your technique for giving insulin injections, the syringe size and needle, along with rotating injection sites, all matter when it comes to managing your blood sugar levels and avoiding complications.

For many people who give themselves daily insulin injections, the syringe and needle size can make a big difference in comfort and staying on track with steady blood sugar levels.

Whether it’s a new experience or you’ve been using insulin injections for a while, it’s good to be familiar with the safest and most effective way to give yourself insulin shots.

It’s important to talk with your doctor if you have concerns about needles and giving yourself insulin shots.

You can also review a few tips on insulin injections here.

There are also options other than syringes available depending on your dose, comfort, and cost factors. Insulin syringes are the least expensive of all the options for insulin delivery.

Your doctor will help you decide the right choice for you. They can also help you practice until you feel confident about giving your insulin dose.

Always dispose of used needles properly. Don’t dispose of needles in the regular trash. Visit to learn more.