Medication administration - Insulin: Nursing pharmacology

Insulin is a hormone secreted by beta cells in the pancreas that helps glucose enter the body’s cells, so it can be used for energy. In diabetes mellitus, insulin is either not produced at all, like in type I diabetes; or cells are resistant to insulin, like in type II diabetes. In either type, glucose can't be utilized by the body’s cells, so it builds up in the bloodstream.   

Exogenous insulin, or synthetic insulin, can be administered to help regulate glucose levels, and is most often administered by subcutaneous, or SUBQ injection. It’s a commonly used, high-alert medication, meaning there’s an increased risk of patient harm if administered in error. This is because insulin can cause potentially dangerous hypoglycemia, or low blood glucose levels. 

Alright, so insulin typically comes in either a vial or a pen. Most insulin vials contain a concentration of 100 units of insulin per milliliter. It’s important to note that insulin doses are prescribed and measured in units, not milliliters so you’ll always use an insulin syringe, which measures increments of insulin in units. Insulin vials can include rapid-, short-, intermediate-, or long-acting insulins as well as pre-mixed solutions like 70/30 preparations, which contain 70 percent intermediate-acting insulin and 30 percent rapid-acting insulin. Most insulins are clear, but a type of insulin called NPH, which is short for neutral protamine Hagedorn is cloudy because a protein called protamine is added to prolong its action in the body over an extended period. 

There are also pre-filled insulin pens, which contain either 150 units of insulin per 1.5 milliliters or 300 units of insulin per 3 milliliters. These devices can be used for multiple injections for one patient. Before administering the insulin, a small disposable needle is placed on the end of the pen and the indicator dial is turned to the correct insulin dose. Following administration, the dose indicator returns to zero and the needle is removed from the skin and discarded.  

Now, let’s review some calculations for subcutaneous insulin using a vial and syringe.   Nurse Nathan works in a long-term care facility and is caring for Alice, an 89-year-old woman with type 2 diabetes. Nurse Nathan checks the electronic health record, or EHR, and sees that Alice is ordered a sliding scale of insulin aspart for subcutaneous injection. He also sees that 10 minutes ago Alice’s blood glucose was 289 mg/dL. According to the sliding scale, Nathan will administer 8 units of insulin aspart. 

Next, Nurse Nathan checks the label of the insulin vial and sees that the vial contains 100 units of insulin per milliliter 

Nurse Nathan then selects an insulin syringe, making sure it’s measured in units.  

Since he needs to withdraw 8 units of insulin from this vial, he first fills the syringe with 8 units of air and injects the air into the vial. This keeps a vacuum from forming so the medication can easily enter the syringe. Then he draws up 8 units of insulin into the syringe. Before administering the dose, Nurse Nathan asks another nurse to check the order, the vial, and the syringe to ensure he’s prepared the correct amount.