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The Mayo Clinic Proceedings in September 2016 published an article titled "New Insulin Delivery Recommendations". It's meant to complement and extend the injection recommendations published in 2010.
Here are a few key points that may not be well known.
Insulin should be injected through the skin and into the fat tissue which is between the skin and the muscle. Studies show that the skin thickness for adults averages 2-2.5 mm and is consistent across age groups, sexes, body mass indexes (BMIs), and geographic locations. In other words, you don't need a longer needle if you have more fat tissue, because your skin thickness is the same as someone who is thinner.
In fact, using too long of a needle can put you at risk for injecting into the muscle instead of the fat, and the insulin absorption rate is different in muscle tissue than in fat tissue.
According to the recommendations, the 4 mm insulin pen needle is long enough to traverse the skin and enter the fat tissue, with little risk of intermuscular injection. It's considered the safest pen needle for adults and children regardless of age, sex, ethnicity or BMI. The safest syringe needle is 6 mm.
When using an insulin pen, don't touch the injector button until the needle is completely inserted. Once the button is pushed, keep pressure on it and count slowly to 10 before withdrawing the needle. If the button is released while the needle is still in the skin, body fluid and cells may be aspirated into the cartridge and cause contamination. Counting to 10 allows time for the pen device to deliver the full dose of insulin and helps prevent insulin leakage.
After use, dispose of needles immediately. Otherwise, air or other contaminants can enter the cartridge or medication can leak out, both of which can distort dose accuracy.
If you use a cloudy insulin (NPH or a premixed insulin which contains NPH), you must "re-suspend" the insulin prior to administration. Avoid vigorous shaking as it produces bubbles that will affect accurate dosing. Gently roll and tip the insulin until the crystals are re-suspended and the solution looks consistently milky throughout. Tipping involves one full up-down motion of the pen or vial and rolling is a full rotation cycle between the palms. Roll the insulin vial or pen between the palms 10 times for 5 seconds, and tip 10 times for 10 seconds.
Lipohypertrophy (LH) is a disorder of the fat tissue which sometimes occurs at frequently used insulin injection sites. It results in swelling or hardness of the tissue. The absorption of insulin into LH areas can be erratic and unpredictable which may lead to high or low blood sugar. And if you switch from injecting into LH tissue to injecting into normal tissue there's a risk for hypoglycemia unless you decrease your dose. To prevent LH, rotate injection sites and avoid re-using needles. You will want to avoid injecting into these areas, but your insulin doses may need to be decreased before you make the change. If you suspect you already have LH, contact your care provider.
As always, if you have questions or concerns about these suggestions or any aspect of insulin administration, contact your health care provider.
Sara J. Carlson, R.N., C.D.E.
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