How long and how thick is the needle for an insulin pen?

In 2011, the first edition of China Diabetes Medicines Injection Technical Guidelines was organized and compiled by the Diabetes Society of Chinese Medical Association for the first time. With the increase of evidence-based medical evidence in the world and in China, after five years, the Diabetes Society of Chinese Medical Association revised the first edition of China Diabetes Medicines Injection Technical Guidelines (2016 edition) in April 2017. The new guidelines add more Chinese research data and updated and more comprehensive recommendations with the gradual development of technology, so that the majority of medical professionals more standardized injection technical guidance, and ultimately more Chinese patients benefit.
How many centimeters is a good choice for an insulin pen needle?
Choosing the appropriate needle length is the key to ensure the safe and reliable injection of insulin into subcutaneous tissue without leakage and discomfort. The choice of needle length should be individualized, including the user's body size, insulin type and so on. The shorter the needle, the higher the safety and the better the tolerance.
The skin and subcutaneous fat thickness of the Chinese population is similar to that of other countries. The average skin thickness is 1.91 mm in the upper arm, 2.10 mm in the thigh, 2.47 mm in the abdomen and 2.68 mm in the buttock. The average skin thickness of women is slightly higher than that of men, and the skin thickness of people with higher BMI is slightly higher than that of people with lower BMI, but these parameters do not affect the choice of needle length. The average thickness of subcutaneous fat was 7.23 mm in the upper arm, 7.37 mm in the thigh, 12.14 mm in the abdomen and 10.48 mm in the buttock. The thickness of subcutaneous fat in females is slightly higher than that in males. The study concluded that vertical needling with a 4mm needle prevented 99% of patients from injecting insulin into their muscles. The longer the needle length, the higher the risk of intramuscular injection, especially in the upper arm. All groups recommend using 4mm needles: 4mm needles into subcutaneous tissue, intramuscular (or intracutaneous) injection risk is minimal, is the safest needle for injection pens for adults and children, regardless of age, gender and body mass index (BMI). Young children and very thin adults should use 4mm needles, needing to pinch the skin vertically, and other people needn't pinch the skin when using 4mm needles; whether or not pinching, 4mm needles should be inserted vertically; if children use 5mm needles, they should pinch the skin; if obese patients use 4mm needles safely and effectively, 5mm needles are acceptable; when pressing the skin, they should avoid depression. To prevent needles from penetrating too deep into muscle tissue. Compared with other long needles, insulin injection with short needles is safer and more effective, and patients feel less pain.
What is the inner diameter of the needle?
The size of the needle is marked by the letter "G" and a number. G stands for the number. The larger the number, the thinner the needle. As the needle becomes thinner and thinner, the resistance of insulin flow increases accordingly, which leads to a slower injection rate, at which time a greater injection force is needed to achieve the original injection rate. At present, new technologies increase the flow rate by keeping the outside diameter of the needle unchanged and increasing its inner diameter, i.e. reducing the thickness of the needle wall, without making the needle vulnerable, and without increasing the breakage and bending of the needle. The guidelines recommend the use of high-flow needles (ultra-thin-walled needles). Compared with the needles with normal tube wall, the pain, bruising, leakage and skin irritation caused by thin-walled needles were mild. Especially because of smaller pressure, shorter injection time and less pain, it is more suitable for diabetic patients.