Insulin is a peptide hormone. This means that is sensitive to temperature changes and its stability is affected by extreme variations.
This is why it is recommended to store unopened vials in the refrigerator at 2-8° C. While vials which are in use can be kept at room temperature for up to about 4 weeks, it must be kept that the temperature must not exceed 25-30° C, depending on the insulin in use.
- Since in hot countries like India, temperatures can regularly exceed these upper limits, thus insulin is often kept in refrigerators when it is in use.
- The problem with this is that sometimes it may make the insulin injection more painful for the user.
- Also, occasionally air bubbles form in the insulin vial or cartridge, and some people find it easier to remove them when the insulin is at room temperature.
- These are however small irritants, which may not be a problem for many people. For them, there is no problem if the insulin is injected after taking it out straight from the fridge.
Manufacturers previously used to recommend Insulin pens not be refrigerated when in use. The reasons cited were, as mentioned above, the more painful injections in some patients with cold insulin, and the difficulty in removing the air bubbles in the colder insulin which some experienced.
However these recommendations have been revised by some manufacturers; so in hot countries, it may be better to keep the pens refrigerated than risk loss of potency due to exposure to higher temperatures than the upper limit of the recommended range.