Why are some patients of diabetes treated by giving injections of insulin?

(N/A) Diabetes is a metabolic disorder characterized by high blood sugar levels (hyperglycemia).
Insulin is a hormone produced by the $\beta$-cells of the pancreas that facilitates the uptake of glucose into cells,thereby lowering blood sugar levels.
In patients with diabetes,the pancreas either does not produce enough insulin or the body cannot effectively use the insulin it produces.
Therefore,external injections of insulin are administered to maintain blood glucose levels within the normal physiological range.