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Using the smallest needle size for pen insulin injectors may be worth considering. If you find using a pen medication injector to be painful, you may be able to eliminate this problem by switching to a different needle size. 18g hypodermic needle
Studies have found short, thin needles deliver insulin as effectively as longer, thicker ones and may be more comfortable to use. Your healthcare provider can help you make an informed decision about whether using a different needle is an option for you and which size to switch to.
This article discusses needle sizes of pen injectors, as well as ways to reduce pain caused by pen injectors.
Smaller needles can refer to the length of the needle and/or the thickness of the needle.
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 could potentially 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 insulin given. In addition, shorter needles may have an advantage over longer needles: People may be less likely to 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 doesn't happen.
For people who need to inject a large dose of insulin at one time, a thicker needle (lower gauge) may deliver the insulin quicker and avoid medication leaking out from the injection site. However, injecting insulin using thicker needles can be more painful.
The thickness of a needle (gauge) and not leaving the needle in the skin long enough are more likely to affect insulin leakage than needle length.
Insulin pen needles range from 4 mm to 12 mm 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 2.1 mm thick, so a 4 mm needle will easily go through the skin layer.
The smallest, thinnest needle is the nano 4 mm, 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 4 mm needle is considered suitable for adults and children. Needles available in this length include:
The 6 mm mini needle usually comes in a gauge of 31 or 32, making it as thin as the 4 mm needle. Options include:
The 8 mm needle is still short and very thin, with an average gauge of 31, but typically requires pinching the skin to get the most accurate dose.
Options for this length include:
The 10 to 12 mm 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 chance that a longer needle such as the 10 mm or 12 mm size may negatively impact thinner patients who have less subcutaneous fatty tissue to get through before reaching the muscle. In fact, 4-, 5-, and 6-mm needles are recommended for all adults with diabetes regardless of their BMI.
Ask your healthcare provider if this length is right for you.
Options for this length include:
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.
There are methods to prevent or lessen pain discomfort while using an insulin pen, regardless of needle size:
Short, thin needles for pen insulin injectors have been shown to cause less pain and deliver insulin effectively. The needle size that is best for you may depend on how much fatty tissue you have and how much insulin is required with each injection. In addition to changing needle size, there are several ways you can reduce injection pain. Talk with your healthcare provider about which needle size best meets your needs.
American Association of Diabetes Educators. Strategies for insulin injection therapy in diabetes self-management.
Hirsch LJ, Strauss KW. The injection technique factor: what you don’t know or teach can make a difference. Clinical Diabetes. 2019;37(3):227-233. doi: 10.2337/cd18-0076
Hirose 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 males. J Diabetes Investig. 2013;4(3):287–296. doi:10.1111/jdi.12035
Præstmark KA, Stallknecht B, Jensen ML, Sparre T, Madsen NB, Kildegaard J. Injection technique and pen needle design affect leakage from skin after subcutaneous injections. J Diabetes Sci Technol. 2016;10(4):914‐922. doi:10.1177/1932296815626723
American Diabetes Association. Insulin pens.
Derraik JG, Rademaker M, Cutfield WS, et al. Effects of age, gender, BMI, and anatomical site on skin thickness in children and adults with diabetes. PLoS One. 2014 Jan 21;9(1):e86637. doi: 10.1371/journal.pone.0086637
O'Neal KS, Johnson J, Swar S. Nontraditional Considerations With Insulin Needle Length Selection. Diabetes Spectr. 2015 Nov;28(4):264-7. doi: 10.2337/diaspect.28.4.264
Food and Drug Administration. Caution when using pen needles to inject medicines: FDA safety communication.
By Barbie Cervoni, RD Barbie Cervoni MS, RD, CDCES, CDN, is a New York-based registered dietitian and certified diabetes care and education specialist.
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