One of the best places to inject insulin is in your belly as it can absorb the insulin quicker and more consistently; this should be a couple of centimetres from the belly button.
But you can also inject it at the front of the thighs, the back of the upper arms, and the top of the buttocks if you’re unable to get to your belly.
You shouldn’t inject at the exact same site each time as it can cause bumps or pits in the skin.