Long-acting insulin is insulin with a relatively long duration of action, also known as basal insulin, which usually lasts for 16-24 hours, and newer insulins, such as ultra-long-acting insulin, can act for even more than 25 hours. Most long-acting insulins are injected at a fixed time before bedtime or in the morning, and the dose of long-acting insulin is adjusted primarily based on fasting blood glucose. Long-acting insulin, with its long duration of action and lack of defined peaks, is also important for overall blood sugar control. Side effects of insulin include hypoglycemia, injection site allergy, weight gain, etc. Insulin allergy is contraindicated. Long-acting insulin should be used under the supervision of a physician.