Understanding Insulin Syringes Sizes - Healthline

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HealthlineSubscribeDoes the Size of an Insulin Syringe Matter?

Medically reviewed by Alana Biggers, M.D., MPH — Written by Malini Ghoshal, RPh, MS — Updated on May 1, 2025

Syringes and injections
Sizes and lengths
How to choose
Why it matters
Takeaway

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.

According to a 2024 statistics report from the Centers for Disease Control, approximately 38.4 million people in the United States have diabetes.

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.

People with type 1 diabetes, and occasionally those with type 2 diabetes, need to take insulin to maintain blood sugar levels.

Insulin can be given in different ways: syringe, pen, or 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 regarding syringes and maintaining steady blood sugar levels.

This article reviews insulin syringes, needle sizes and lengths, and why it matters.

What to know about insulin syringes and injections

Here are a few things to keep in mind when buying and using insulin syringes.

One-time use. 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.
Rotate sites. It’s also important to rotate injection sites. This will help you avoid lipohypertrophy (an abnormal fat deposit under the skin), a common complication with daily insulin injections.
Subcutaneous injection. 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.

Sizes and lengths of insulin syringes and needles

Insulin syringes come in multiple sizes with different needle length options. 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 syringes 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 the muscle. Shorter needles are safer to avoid going into the muscle.

Syringe and needle sizes and lengths

The International Scientific Advisory Board for the Third Injection Technique Workshop states that there is no medical reason to use a needle longer than 8 mm.

According to the Advisory Board, the most recommended needle sizes are 4 mm, 5 mm, or 6 mm. However, larger sizes may also be needed in certain scenarios. They recommend choosing needle sizes on a case-by-case basis.

A 2020 study found that most users prefer shorter needles ranging from 4 to 9 mm in length. And a 2015 study found that people generally liked using thinner needles as they were less painful and easier to insert.

The following table provides information on the barrel size and volume, needle length, and gauge for various sizes of needles and syringes.

Barrel size (syringe fluid volume)	Insulin units	Needle length	Needle gauge
0.3 mL	< 30 units of insulin	3/16 inch (5 mm)	28
0.5 mL	30 to 50 units of insulin	5/16 inch (8 mm)	29, 30
1.0 mL	> 50 units of insulin	1/2 inch (12.7 mm)	31

Choosing the correct syringe needle size for your dose

The correct needle size depends on your insulin dose and your comfort level. 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.

If you give different doses per day, you may need multiple syringes. For example, 35 units in the morning and 10 units at night mean 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 syringe’s maximum capacity, you may want to go up a size to avoid difficulties handling it.

Why syringe size and length matters

Studies on insulin needle size have shown that body mass index (BMI) doesn’t matter when it comes to how long a needle should be 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 been shown to provide accurate dosing. If you don’t like big needles, this may improve your comfort level with giving yourself insulin injections every day.

Thinner gauge needles may also be less painful, especially if you need daily injections. Consider discussing needle size options with your doctor. They can help choose a size and length that’s appropriate for you and your daily insulin needs.

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.

»Read more about where and how to inject insulin

The takeaway

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.

Depending on your dose, comfort, and cost factors, other options are also available. Insulin syringes are the least expensive option for insulin delivery.

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

How we reviewed this article:

SourcesHistoryHealthline has strict sourcing guidelines and relies on peer-reviewed studies, academic research institutions, and medical journals and associations. We only use quality, credible sources to ensure content accuracy and integrity. You can learn more about how we ensure our content is accurate and current by reading our editorial policy.

Al Hayek AA, et al. (2020). Evaluating the user preference and level of insulin self-administration adherence in young patients with type 1 diabetes: Experience with two insulin pen needle lengths.https://pmc.ncbi.nlm.nih.gov/articles/PMC7370678/
Cefalu WT, et al. (2018). Insulin access and affordability working group: Conclusions and recommendations.https://care.diabetesjournals.org/content/41/6/1299
Hirsch LJ, et al. (2019). The injection technique factor: What you don't know or teach can make a difference.https://diabetesjournals.org/clinical/article/37/3/227/32887/The-Injection-Technique-Factor-What-You-Don-t-Know
National diabetes statistics report. (2024).https://www.cdc.gov/diabetes/php/data-research/index.html
Yamada S, et al. (2015). A comparison study of patient ratings and safety of 32- and 34-gauge insulin pen needles.https://pmc.ncbi.nlm.nih.gov/articles/PMC6224982/

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Medically reviewed by Alana Biggers, M.D., MPH — Written by Malini Ghoshal, RPh, MS — Updated on May 1, 2025

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Understanding Insulin Syringes Sizes - Healthline

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What to know about insulin syringes and injections

Sizes and lengths of insulin syringes and needles

Syringe and needle sizes and lengths

Choosing the correct syringe needle size for your dose

Why syringe size and length matters

The takeaway

How we reviewed this article:

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