The insulin pen should stay under the skin for at least 10 seconds after injecting insulin. The principle of using insulin pen for subcutaneous injection of insulin in diabetic patients is to push the insulin cartridge to be injected into the subcutaneous through the action of the piston rod, the recovery process of the rubber piston itself will take some time, coupled with the thin injection needle, when the medicine is injected into the body for a longer period of time, so when the insulin is injected by using the insulin pen for the injection of insulin, it is common to see that there will be a situation of pulling out the needle and there will be ooze around the needle.1 grain. round ooze is roughly equivalent to 2 units of insulin, so in order to ensure the accuracy of the insulin injection dosage and avoid wastage of the medicine, after injecting insulin with an insulin pen, it should be left under the skin for at least 10 seconds and you need to continue to hold down the push button before pulling out the needle in order to avoid oozing from the needle.