All About Insulin
By MJ Wainwright, RN
Tuesday, April 19, 2005All About Insulin
Insulin is a hormone made in the pancreas that helps to regulate the body’s blood sugar. Special cells called "beta cells" within a part of the pancreas called the Islets of Langerhans actually produce the insulin (therefore the insulin producing cell are often called islet cells). When a person has Type I diabetes only the insulin producing cells are affected, the other cells within the pancreas function normally. Insulin has three main functions. First, it allows sugar to pass into the cells where it can be used for energy. Secondly, it turns off sugar release from the liver and reduces production of sugar in the liver and muscles. Also, it turns off the body's signal to break down fat for fuel (lipolysis).
People with Type I diabetes no longer make insulin. It must be given to the person by an injection. The management of Type I diabetes usually requires 2 or 3 daily injections of different combinations of short acting and long acting insulin to control the persons blood sugar (more injections may be used with some regimens). The purpose of using both short and long acting insulins is to mimic the body’s normal production of insulin. This is furthered by the use of genetically engineered insulin identical to human insulin. Review the tables on short and longer acting insulins. Pay attention to the "onset of action" and the "peak of action" times. These "times" are important in the controlling blood sugar highs and lows.
The normal human body secretes a small (basal) amount of insulin at all times dependent upon the body’s blood sugar and level of activity. A larger (bolus) amount of insulin is provided naturally by the body after a meal to allow the increase of sugar in the bloodstream to get into the cells or to be stored for future use. In Type I diabetes injections of the longer acting insulins provide the basal amounts for the body and the short acting insulins provide more coverage of meals and snacks. Again, the purpose is to mimic the normal body. But because the insulin is only provide at certain times, the Type I diabetic must schedule his/her meal pattern to match the onset and peak times of the insulin so that extremes of high or low blood sugar can be avoided. When you review the diagram on insulin activity you will see why it is important for the type I diabetic to remain on a fairly rigid schedule.
It is important to be aware that insulin action (when it peaks and how long it lasts) may vary from person to person. There also may be variability due to exercise, injection site, stress, illness or hormones. The best control is achieved by monitoring blood sugar levels and adjusting insulin dosage accordingly.
Short Acting Insulins
Humalog or Novolog (Lispro) starts to work in 10 to 15 minutes. It’s main (peak) effect lasts up to 90 minutes. There may be some lingering effects as long as 4 hours.
Regular insulin starts to work around 30 minutes after injection, peaks in 2 to 4 hours and lasts from 4 to 8 hours.
Longer-Acting Insulins
NPH (Neutral Protamine Hagedorn) is made with a protein to slow absorption. NPH starts to work in 2 hours and peaks 6 to 8 hours after injection. The average duration is about 13 hours.
Ultralente Insulin is another long acting insulin. Ultralente begins working in 4 hours providing it's main effect over 8 to 15 hours and dissipates over 18 to 24 hours.
Lantus insulin (insulin glargine) is the newest long acting insulin. It is the most effective "basal" insulin. This means it has very little peak effect, but acts over 20-24 hours. Lantus is given at bedtime with Humalog or Novolog administered before meals. This regimen will give very good blood sugar control but it requires at least 4 shots per day. Also, Lantus cannot be mixed with any other insulin.
Insulin is sensitive to extremes in temperature. Insulin also becomes "weaker" over time. When patients are insulin dependant, it is important for the insulin to be as effective as possible. Therefore, it is recommended that insulin vials should only be used for a maximum of 6 weeks. Your doctor will prescribe enough insulin so that each vial can be changed monthly.
All U.S. insulins are measured in units. All insulins made in the U.S.A. are standardized to contain 100 u (units) per cc. Only insulin syringes should be used when administering insulin because they are measured in units and specially made with fine/short needles for people who receive frequent injections. Most doctors recommend that syringes be used only once, then discarded. If very careful technique is maintained for cleanliness, a syringe may be used again. However, the very fine syringes that are used with children will be less sharp (and more painful) after a single use.
Syringes must be disposed of in a manner that will not cause harm to anyone else. Please do not throw used syringes in the trash! Syringes and lancets should be placed in a puncture proof container (like a coffee can). When the container is filled it should be sealed with tape, labeled as insulin syringes, and placed in the regular trash. Some cities require that syringes be disposed of in approved biomedical waste containers. These can be purchased at any pharmacy.
MJ Wainwright, CCRN
Fountain Valley Community Hospital
Inservice - June 21, 2001
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