NPH refers to medium-acting insulin, mainly low argin insulin and slow insulin zinc suspension, commonly used such as Novolin N, which is formed by combining insulin with zinc oxide and protein-like substances, mainly used to provide basal insulin, which can control the blood sugar before two meals and at night to maintain stability. Neutral insulin has the characteristics of slow onset and long duration of action, with onset of action in 2.5-3 hours, peak time in 5-7 hours and duration of action in 13-16 hours, and the duration of action is between short-acting insulin and long-acting insulin. Since neutral insulin is a white suspension liquid containing insoluble crystals with peak concentration, it should also be gently shaken before injection so that it can be well mixed.