How the Size of Pen Needles May Affect Diabetes Control

Longer Is Not Better

Injectable medications such as insulin and glucagon-like peptide-1s (GLP-1s) are most effective when injected just below the skin into fatty tissue so the body can easily absorb and use it. Therefore, a long needle isn't necessary. In fact, if insulin is injected into muscle tissue it will be used up more quickly than is ideal, which potentially could lead to hypoglycemia. What's more, if a needle pierces muscle tissue it can cause pain, bruising, and bleeding.

Studies show needle length doesn't affect blood sugar control. Needles as short as 4 millimeters [mm]) do not appear to impact the function of administered insulin and may actually have advantages over longer needles, since again, they're can't reach muscle tissue, making it less likely people who used insulin will skip self-injections to avoid pain.

Some people with diabetes worry that a shorter needle may allow insulin to leak from the injection site, but research has shown this to be an unfounded concern.

The thickness of a needle—gauge—and not leaving the needle in the skin long enough are more likely to affect insulin leakage than its length.

Needle Sizes

Insulin pen needles range from 4mm to 12mm in length and 29 to 32 gauge in diameter. The lower the number of millimeters, the shorter the needle, while the higher the gauge, the thinner the needle. On average, human skin is 1.6 mm to 2.5 mm thick, so a 4mm needle will easily breach the skin layer.

4mm

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, which should not require pinching the skin while injecting (done to pull the fatty tissue away from the muscle for a more accurate injection).

The 4mm is considered suitable for adults and children. 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

The 6mm mini needle usually comes in a gauge of 31 or 32, making it as thin as the 4mm option. Options 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 typically requires pinching the skin to get an most accurate dose.

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

10mm to 12mm

The 10 to 12mm length was once the standard needle size, and many people are still accustomed to this length. These needles are very thin, with a gauge size ranging from 29 to 31. 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

The Food and Drug Administration cautions against removing both the outer and inner needle covers from standard pen needles—and paying special attention to needle technique when switching needles, so as not to receive an underdose.

Reducing Injection Pain

To prevent or lessen pain discomfort while using an insulin pen, regardless of needle size, you can:

Let insulin come to room temperature. Cold insulin can sting—remove it from the fridge 15 minutes before injecting.
Allow the alcohol to dry. If you use 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.
Don't jabs. Rather, aim for quick, direct penetration. Inject at a 90-degree angle to your skin and do not change the direction of the needle once you are in the injection site.
Rotate injection sites. Move the injection site by one inch with each dose to prevent soreness, irritation, or formation of a painful lump.
Press, don't rub. If an injection hurts painful, apply pressure to the site for a few seconds, but do not rub it: This could increase insulin absorption and put you at risk of hypoglycemia.

A Word From Verywell

Always use a new needle for each injection, as repeated use of the same needle increases the 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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