Generally insulin needles with a 6 mm tip can be hit vertically, but for thinner stature or when choosing limb areas for injection, the skin needs to be pinched up to form a skin fold before injection, or the needle should be taken in at an angle (45° angle) in order to replace pinching the skin and then injecting.
Insulin pens have different lengths of injection needles, of which 6 mm is a certain length of insulin pen needles. Since 6 mm needles are not too long and act on the subcutaneous tissues during vertical injections, it is sufficient to administer the medication vertically when injecting with 6 mm insulin needles.
The 4-mm, 5-mm, and 6-mm needles are suitable for all adult patients, including obese patients, and usually do not require pinching of the skin during injection, especially with the 4-mm needles. For injections in adult patients, the needle should be introduced perpendicularly at 90° to the skin surface.
For the majority of the population, a 4 mm needle can be used without pinching the skin and injected at 90°; for thinner people or when injecting in the extremities, especially with 5 or 6 mm needles, it is necessary to pinch the skin to form a skin fold before injecting in order to avoid intramuscular injections, or to inject at an angle (45°) instead of pinching the skin.
Diabetics who are unsure of how to inject insulin are advised to consult a healthcare professional at a hospital.