Although, people with T1D know how to use an insulin pen, still there are many people out there getting diagnosed every other day and are newbies to the same, so I would like to mention some basic steps of how to use an insulin pen and safeties associated with them-

How to use Insulin pens-

1. Open the lid of the Insulin pen and if you are using any insulin which is a mixture of two ( For example – Human Mixtard, which is a mixture of fast acting and long acting insulin ), you have to rub the insulin pen well between both the palms. 
2. Remove the paper tab and screw it to the pen. Now remove the outer and inner cover of the needle and it’s ready for use.
3. Now look for any air bubble in the insulin cartridge. If you see any air bubble hold the pen needle facing upwards and remove the air until a drop of insulin appears.
4. It’s time to dial your dose. Be careful while you are dialling your dose (In some older version of pens you can’t dial backwards but these days in almost all pens you can dial both forward and backward ).
5. Choose your injection site now, whether it is abdomen, upper arm or thighs. Disinfect the area with an alcohol swab and allow it to dry.
6. After disinfection of the injection site, you can now inject the insulin. Firstly, pinch a small area before injecting, insert the needle at 90 degrees and release the pinch. Slowly press the push button on your insulin pen and deposit the desired dose as dialled. After injecting the full dose, leave the needle there for 10-20 seconds, so no insulin oozes out and wasted after you remove the needle.
7. Now, place the outer cover of the needle safely and you’re done! 

    

    

Safeties associated with Insulin pens are quite simple to learn and follow. 

1. The very first rule is never share your pen with anyone.
2. Keep changing your needles. Never use same needle for a longer period of time as it will damage the tissues on the injection site, as the needle after each use loses its sharpness and become blunt (Note- Ideally, needles are meant for single use, but I usually use them for 2-4 shots)
3. Never leave your pen with open needle neither store. In any case if lid of your needle is misplaced, immediately replace your needle with a new one.
4. When you are on MDI regime, always keep a check on which insulin you are injecting. Sometimes, patients especially kids mistakenly inject short acting insulin in place of long acting and vice versa. So, always keep your pens in respective cases and be attentive while you are taking shot.
5. Always keep an eye on the reservoir. Insulin pens are always provided with a window that will show you the amount of insulin remaining. This will help you fetch another set of cartridges in advance. 
6. Usually dispensing your dose with a pen is quite easy, but if at all you feel your pen is missing that ease, think of getting a new one. This happened to me once, one day when I was taking my shot like some other days, I felt a resistance while injecting the insulin, I thought something must have been wrong with my usage but following doses were real hard for me and very morning I was just unable to dial my dose and inject the same. I immediately rushed to the store from where I had purchased that pen and they said that something went wrong with the plunger, that is why I felt resistance and nothing can be done with it and eventually I had to change my pen. ( Note – If possible, always keep an extra pen as a stock with you ).