At first insulin recommended to be injected into some sites where a less-sensitive layer of fatty tissue just below the skin to absorb the insulin with no many nerves ,so that insulin injection will be more comfortable in these sites more than others the just under the skin.
Also these sites make it easier to inject into the subcutaneous tissue, where insulin injection is recommended.
Common sites for insulin injection are :A-Abdomen :the most common insulin injection site because it has easily accessible fatty areas and Insulin is absorbed faster when it is injected into the abdomen " So:you should inject the insulin into the abdomen just before meals",Also This area allows for greater access if injecting individually.
Notes:Do not inject within 1-2 inches around the navel "tissue is tough" ,surgical, other scar tissue, moles.
B-Thighs :The middle and outer thigh area is another one of the common insulin injection sites that are suitable for injecting long-acting insulin.Don't inject too close to the area just above knee because the tissue is very tough.
C-Arms :The back of the upper arm