Some people who need both long-acting and short-acting insulins use premixed insulins such as Humulin 50/50, Humulin 70/30, Novolin 70/30, Humalog Mix 75/25, or NovoLog Mix 70/30. A dose of 50 units of Humulin or Novolin 70/30 provides a combined basal, intermediate-acting insulin (NPH) dose of 35 units and a bolus, short-acting insulin (Regular) dose of 15 units. Other people mix their own long-acting and short-acting insulins or take each separately.
If you are considering insulin therapy or if your health-care team is recommending insulin therapy, you’re probably wondering about the day-to-day mechanics of using insulin. Although this is not an exhaustive list, it may help you to get an overview of the subject.
Timing of injections. Taking your injections around the same time of day is important because insulin formulations release insulin into your system over a period of time, and although some basal insulins maintain a rather constant level of insulin in your bloodstream, other increase, peak, and decrease. If you inject your NPH insulin at 6 PM one night and 11 PM another night, you will see potentially wide variations in your blood glucose levels.
The rapid-acting insulins aspart and lispro can start to lower your blood glucose within five minutes of an injection, so they should be taken just before or after meals. If you wait too long to eat after injecting aspart or lispro, your blood glucose level could drop too low.
Mixing insulins. Insulin glargine (Lantus) cannot be mixed in the same syringe with any other insulin. All of the other insulins can be mixed together but if you mix Lente or Ultralente with any other insulin product, you must inject immediately after filling the syringe; if you don’t, the action profile—or the time it takes the insulin to start working, reach peak effectiveness, and taper off—will change.
Insulin delivery systems. Insulin is injected into a fatty part of the body so that the blood supply that feeds fat can absorb the insulin for use in the body. A syringe filled with insulin from a vial is the traditional method of delivering insulin. Pen-shaped devices called insulin pens, which are either prefilled with insulin or loaded with a cartridge of insulin, are also used. Devices prefilled with insulin called insulin dosers, which have a large display or dial for easier measurement of insulin doses, are also available.
The insulin delivery system that you choose to use can be based on your preferences, cost of the system and reimbursement, manual dexterity, visual acuity, and your unique lifestyle issues.
Storage. All insulin vials or pens not in use should be stored in the refrigerator. Most opened vials of insulin can be stored at room temperature for up to 28 days, after which they should be discarded. Prefilled insulin pens, insulin dosers, and insulin cartridges have very specific room temperature storage guidelines of 7, 10, 14, or 28 days depending on the type of insulin. Insulin stored beyond the room temperature storage guideline may be significantly less effective if used.
Checking blood glucose levels. There is no exact formula for deciding on an insulin dose, but one of the key factors used in regulating insulin doses is your blood glucose level. Blood glucose monitoring becomes an indispensable tool when you make the transition to insulin therapy. How often you need to check your blood glucose depends at least in part on the type of insulin prescribed. Plan to check more frequently when you first begin insulin therapy so that adjustments to your regimen can be made.
The most common side effect of insulin therapy is hypoglycemia, or low blood sugar. Hypoglycemia is also a side effect of the sulfonylureas, the pills that stimulate the pancreas to secrete more insulin. Most episodes of hypoglycemia can be traced back to one of the following: taking too much insulin or oral medicine, skipping or delaying a meal, exercising strenuously without having a snack or carbohydrate drink, and drinking alcohol. Common signs and symptoms of hypoglycemia include sudden weakness, shaking, sweating, headache, hunger, palpitations, confusion, blurred vision, and irritability.