Freezing Insulin; Injection Changes
As someone who's had type 2 diabetes for 20 years, I often wonder about two things we are told about insulin use. 1. Why are we told to never freeze insulin and never to use insulin that has ice crystals in it? What if the insulin had been frozen, or partially frozen, at one time, but is now fully defrosted? Is it more dangerous to use insulin that might have been frozen at some point, or to do without? 2. When I first started injecting, I was told to draw back on the syringe to make sure that no blood came back into the barrel. But now, more and more, we see insulin pens, as well as other injectable medications (such as Byetta), that we cannot draw back on. I'd like to know why it supposedly was an important step previously, but no longer is. Sydney Barouch, Flushing, New York
Jan McWilliams, RN, MSN, CDE, BC-ADM, responds: Whenever insulin freezes (below 36°F) it forms crystals and clumps. This affects the molecular structure and thereby the effectiveness of the insulin. You shouldn't experience immediate physical harm, but with the loss of insulin potency, your blood glucose would likely go up.
Insulin vials, either opened or unopened, generally last for one month when stored at room temperature (59° to 86°F). A bottle is considered open after the first insulin syringe punctures the rubber stopper. Normally, the open bottle of insulin is kept at room temperature while unopened vials are kept in the refrigerator. When unopened and refrigerated, the vials are good until the expiration date. Insulin should not be allowed to sit in the sun or be exposed to temperatures greater than 86°F as this also could affect its potency. Finally, before using insulin, you should always examine the vial. Insulins that are supposed to be clear (all insulins except NPH and the pre-mixed insulins) shouldn't look cloudy. The vial shouldn't have clumps or anything floating in it, and it should not have a frosted appearance. It should not have changed color or appearance compared to when you first started using it. NPH and pre-mixed insulins should look uniformly cloudy when you mix them, and should also not contain clumps or small particles.
If using a pre-filled insulin pen or insulin cartridges with a re-usable pen, storage life at room temperature can range from 7 to 28 days depending on type of insulin. Insulin pens or cartridges already in use should be kept at room temperature. Pens or cartridges that have not had the seal punctured should be kept in the refrigerator. Consult the package insert or check with your health care professional for directions for your specific insulin. Don't forget to also examine the insulin pen for changes in color or appearance as discussed above.
As for your second question, I have been a nurse for 35 years, and you are correct that we once taught our patients to aspirate insulin syringes before injecting the insulin. This was to avoid injecting the insulin into a blood vessel and was, at the time, the practice for giving any injection. However, insulin syringe technology has improved, and needles have become shorter and finer. Since insulin is given subcutaneously (into the skin), there is little chance of hitting anything other than a small capillary with your syringe. If you do have bleeding at your site of injection, it is likely from nicking a capillary. Just put pressure on the site until the bleeding stops. If this happens often, you may want to talk with your diabetes educator about some tips for improving your injection technique.