Allergic reaction may occur 30 minutes after the injection, but this is very rare, other side effects usually appear after a few days of continuous injection, the specific time of side effects vary from person to person. 1. Ascorbic acid injection is the common name of human granulocyte colony-stimulating factor, which is mainly used for tumor patients with leukopenia after chemotherapy, and is injected within 24 hours to 48 hours after chemotherapy. Generally, the drug concentration in the blood reaches the peak after 30 minutes of intravenous drip, and obvious side effects such as allergic reaction start to appear. If the patient is more sensitive to the drug, the side effects will appear earlier and last longer. 2. Common side effects are bone and muscle pain, at this time you can improve the symptoms through localized hot compresses, if the pain is more serious, you can use some painkillers under the guidance of the doctor. During the period of rapid recovery of white blood cells, some patients will have high fever, skin rash and other symptoms, it is recommended to use corticosteroids under the guidance of a doctor to improve the symptoms. Note: Patients should use medication under doctor’s guidance and should not use medication without authorization. Patients are advised to seek immediate medical attention if they experience strong discomfort.