Once a vial of insulin is opened, how long is it good?
Always check the date imprinted on the box for expiration date. Write the date the vial is opened on the vial and discard after 1-3 months from the date of opening. Insulin is a hormone that can be denatured when exposed to extremes in temperatures or by movement. The repeated use of an insulin vial can also slowly denature the insulin and potency is decreased. The more often the bottle is used, the more it is predisposed to denaturing. If blood glucose levels are raising without explanation, check the date on the bottle of insulin; it may be that it’s not as potent. It may be a good idea to “rotate” vials of insulin that are used infrequently at school. Discuss this with the parent and decide how frequently the vials should be rotated. The vials can then be used at home long before the shelf life has expired. Unopened insulin is usually good for two years.