Insulin is available in the market today in two commonly used specification dosage forms. One is insulin that needs to be taken with a 1ml syringe for subcutaneous injection, which is usually 10ml and contains 400 units of insulin, that is, 1ml contains 40 units of insulin. Only this concentration of insulin can be extracted with a 1ml syringe and injected subcutaneously. The other type of insulin, which is commonly used nowadays, is the insulin that needs to be injected into the insulin injection pen, and its specification is 300 units of insulin in 3ml, that is, 100 units in 1ml. The concentration of this insulin is relatively high, so it cannot be injected subcutaneously through a 1ml syringe, but can only be injected subcutaneously using a standard insulin pen.