Insulin Dosing and Administration Protocols

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 case, 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.

Now, let's look at an example where you'll mix two types of insulin.

Nurse Ben is a home health nurse caring for Chris, a 37-year-old patient with type 1 diabetes. Nurse Ben checks the medication order which reads: Insulin regular 5 units and insulin NPH 5 units SUBQ once at 1400.

Next, Nurse Ben checks the insulin vials and sees that both insulins contain a concentration of 100 units per milliliter and the regular insulin has a clear appearance while the NPH insulin appears cloudy. He also checks the drug handbook to confirm that these two types of insulins can safely be mixed in one syringe.

Nurse Ben knows that when drawing up two types of insulins in one syringe, he will always draw up regular insulin prior to NPH insulin; or CLEAR before CLOUDY. This is to prevent accidental injection of NPH into the vial containing regular insulin.

So first, Nurse Ben injects 5 units of air into the NPH vial. Then he injects 5 units of air into the regular insulin vial and withdraws 5 units of the clear, regular insulin. With the same syringe, he withdraws 5 units of cloudy NPH insulin. Before administering the dose, Nurse Ben asks another nurse to check the order, the vials, and the syringe to ensure that he's prepared the correct amount.

Now let's look at how to administer insulin using an insulin pen.

Nurse Josie is working on a telemetry unit and is caring for Holly, a 62-year-woman with type 2 diabetes. Nurse Josie checks the electronic health record, or EHR, and sees that Holly is ordered 3 units of insulin Lispro subcutaneously three times daily before meals.

Nurse Josie then checks the supplied insulin pen which has 100 units of insulin per milliliter. To administer the dose, Nurse Josie turns the dial until the number 3 is displayed in the center of the dose window. This means the pen will inject 3 units of insulin when the plunger is compressed. Before administering the dose, Nurse Josie asks another nurse to check the order and the pen to ensure that she's prepared the correct amount.

Alright, as a quick recap... Insulin is a hormone normally produced by the beta cells in the pancreas. Exogenous insulin, or synthetic insulin, is most often administered subcutaneously. Insulin for subcutaneous injection can be prepared in a vial or pen. All insulin doses are measured in units, and you'll always use an insulin syringe.