Insulin is sensible against environmental impacts. Not used insulin should be stored in the “vegetables” compartment of the refrigerator at 4-8°C. Take care that it never freezes (even not for a short time).
To prevent burning sensation caused by injection of cold insulin you can store the bottle, vial or syringe with insulin in use at room temperature making sure that it is protected against direct sunlight and heat. The full effect if insulin is ensured over a period of a minimum of 4 weeks.
If you have to stay at very low or high temperatures for a longer time, e.g. when travelling, it is recommended to store insulin in an isolating container from foam or styropore.
If stored appropriately the visual nature of insulin must not change. Insulin changed in its visual nature looses its blood sugar lowering effect and must not be used in any case. Take care about it when travelling in summer in hot regions.