Allergic reactions are rare. Storage and safety. Using cold insulin can make your shot more painful. You can keep the bottle of insulin you are currently using at room temperature or warm the bottle by gently rolling it between your hands before you fill the syringe. If you buy more than one bottle of insulin at a time, store the extra bottles in the refrigerator until you start to use them.
Extreme temperatures destroy insulin.
Do not put your insulin in the freezer or in direct sunlight. Insulin may lose some potency if the bottle has been opened for more than 30 days. Look at the bottle closely to make sure the insulin looks normal. If you use NPH or lente, it should be cloudy, with no floating pieces or crystals on the bottle. Do not use insulin past the expiration date.