How the Size of Insulin Pen Needles May Affect Diabetes Control

Man injecting himself with insulin in belt area

 Trish Gant / Doring Kindersley / Getty Images

If you're missing insulin injections because of injection discomfort or pain, it's important to assess your needle size and length and talk to your physician about switching to a shorter, thinner needle, of which there are several options.

Shorter Needles Are Still Effective

No one needs to feel pain when injecting insulin or other medications. Because injectable medications for diabetes, such as insulin and glucagon-like peptide-1s (GLP-1s), should be injected below the skin into fatty tissue and not into a vein or muscle, an extra-long needle is not necessary.

In fact, studies have shown that glycemic (blood sugar) control does not change based on needle length. As well, shorter needle lengths (as small as 4 millimeters [mm]) do not appear to impact the function of administered insulin. Studies say these shorter needles may actually improve dosage. With a shorter needle, there also seems to be no difference in insulin leakage, no matter the person's age, sex, race, or body mass. And more importantly, people who use shorter needles are more likely to not miss injections.

Types of Needle Sizes

Insulin pen needles are measured by diameter (thickness) and length. Most pen needles range from 4mm-12mm in length and 29-32 gauge in diameter. The lower the number of millimeters, the shorter the needle, while the higher the gauge, the thinner the needle. The average thickness of human skin is 1.6 millimeters to 2.5 millimeters thick, so a 4mm needle will certainly breach the skin layer.

Before switching to another needle size, be sure your selection works with your current insulin pen device.

4mm Needles

The smallest, thinnest needle is the nano 4mm, 32 gauge needle, which is about as thin as two strands of hair. The risk of injecting into muscle tissue is very rare when using this needle. In fact, the manufacturer of the BD ultra-fine nanoneedle suggests that when using this needle you don't even need to pinch the skin while injecting. However, it's still important to inject at a 90-degree angle and hold the needle at the injection site for at least 10 seconds.

Options in this length include:

  • GlucoRx 4mm: FinePoint Pen Needles Universal Fit 4mm 31G
  • BD Micro-Fine Pen Needles 4mm
  • NovoFine Plus 32G 4mm

6mm Needles

The 6mm mini needle usually comes with a gauge of 31 or 32, making it just as thin as the 4mm option. Most experts recommend 6mm as the best choice for children with diabetes, and its short length reduces the risk of injection into the muscle, which could lead to hypoglycemia as the rate of absorption will increase and the duration of action will be shortened.

Options in this length include:

  • Unifine Pentips 6mm
  • Novofine Pen Needles 6mm
  • MyLife Penfine Needles 6mm
  • GlucoRx FinePoint Pen Needles Universal Fit 6mm 31G

8mm Needles

The 8mm needle is still short and very thin, with an average gauge of 31, but it's just slightly longer than the 4mm or 6mm needle. With this length, you may need to pinch the skin to get the most accurate injection.

Options in this length include:

  • GlucoRx FinePoint Pen Needles Universal Fit 8mm 31G
  • BD Micro-Fine Pen Needles 8mm
  • MyLife Penfine Needles 8mm
  • Novofine Pen Needles 8mm
  • Unifine Pentips 8mm

10 to 12mm Needles

The 10 to 12mm length used to be the standard needle size, and many are still accustomed to this length. These needles are very thin: gauge size may range from 29G to 31G. There's a small chance that a longer needle such as the 10mm or 12mm size may negatively impact thinner patients who have less subcutaneous fatty tissue to get through before reaching the muscle. Ask your doctor if this length is right for you.

Options in this length include:

  • Unifine Pentips (10mm)
  • MyLife Penfine Needles (10mm)
  • FinePoint Pen Needles Universal Fit 10mm 31G
  • FinePoint Pen Needles Universal Fit 12mm 31G
  • BD Ultra-Fine Pen Needles 12.7mm 29G

Tips For Reducing Injection Pain

There are several controllable factors that can help to reduce pain at the injection site.

  • Let your insulin come to room temperature. Injecting cold insulin can sometimes sting—let your insulin sit at room temperature for 15 minutes before injecting.
  • Allow the alcohol to dry. If you are using alcohol to clean and prepare your injection site, allow it to dry before injecting your insulin.
  • Try not to tense up. Before injecting, take deep abdominal breaths and mentally work to relax the muscles at the site where you'll be injecting. Do not inject into muscle, but aim to relax the muscle around the fatty tissue you are injecting for more comfort.
  • Skip the jabs. Rather than forcefully jabbing the needle into your skin, use a quick, direct penetration. Inject at a 90-degree angle to your skin and avoid changing the direction of the needle once you are in the injection site.
  • Rotate your sites. Be sure to rotate your injection site by one inch with every dosage to prevent soreness, irritation, or formation of a painful lump.
  • Try to avoid rubbing. If a particular injection seems painful, you can apply pressure at the site for a few seconds, but do not rub it. Rubbing the injection site can increase insulin absorption and put you at risk of hypoglycemia.

A Word From Verywell

Remember to always use a new needle for each injection, as repeated use of the same needle increases your risk of infection and may cause the needle to weaken. A weak needle may bend or break during injection or become dull, leading to bruising or bleeding. It's also important to properly dispose of used needles in a specially marked sharps container for medical waste.

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Article Sources

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  2. AMAHirose T, Ogihara T, Tozaka S, Kanderian S, Watada H. Identification and comparison of insulin pharmacokinetics injected with a new 4-mm needle vs 6- and 8-mm needles accounting for endogenous insulin and C-peptide secretion kinetics in non-diabetic adult malesJ Diabetes Investig. 2013;4(3):287–296. doi:10.1111/jdi.12035

  3. Gibney MA, Arce CH, Byron KJ, Hirsch LJ. Skin and subcutaneous adipose layer thickness in adults with diabetes at sites used for insulin injections: implications for needle length recommendations. Curr Med Res Opin. 2010;26(6):1519-30. doi:10.1185/03007995.2010.481203

  4. American Association of Diabetes Educators. Strategies for insulin injection therapy in diabetes self-management. Updated 2011.