by Michael R. Cohen, R.Ph.
If a diabetic patient has poor vision, as many elderly who suffer with the disease do, and they also require insulin injections, knowing when a vial is about to be empty is crucial. This hit home with us a few weeks ago when we heard about a homebound woman who was unable to control her blood sugar, even after increasing her doses of insulin.
A homecare nurse visited the woman to try to figure out what might be leading to the constant need for more insulin. The woman had been eating her usual diet and had no sign of infection, which often increases the need for insulin. She hadn’t decreased her normal level of physical activity, which also can influence blood sugar and she was also sleeping well and there was no new stress in her life. Furthermore, the technique and materials she used to test her blood sugar were appropriate. Any one of these factors could influence the dose of insulin required to keep her blood sugar under control, but nothing unusual was discovered.
The woman had poor vision, though. So the nurse asked her to show her how she measured her insulin doses each day. The woman used a special magnifier to see the syringe markings clearly. But as she lifted the vial to withdraw a dose of insulin, the nurse realized that the vial was empty. For an undetermined time, the woman had been injecting air, not insulin.
Not only was this woman’s blood sugar uncontrolled, she also could have suffered severe low blood sugar when she eventually began using a new vial of insulin, because the doctor had doubled her insulin dose when he thought she was taking the correct dose.
Almost every vial of U-100 insulin has a 10 mL volume so it contains 1,000 units. The vial will remain usable for up to 4 weeks after it is first opened and used. If less than 50 units are left in an insulin vial, it becomes easier to draw air into the syringe instead of the insulin without notice. So, in most cases, a patient will use only 950 units of insulin from each new vial. You can time a vial by adding up the total amount of insulin you typically use in one day. Then divide 950 units by your total daily dose. For example, if you use a total of 50 units of insulin per day, you would divide 950 by 50, which equals 19. That means a vial of insulin should last you about 19 days.
If the dose does not divide exactly into 950, round the number down to the lowest whole number. So even if you only take 48 units of insulin per day, you will still use the vial for only 19 days. The number of days should never exceed 28 days because the insulin is only good for 4 weeks after it is opened.
To help keep track of when to change your vial of insulin, count out the number of syringes you would use over the total number of days and set them aside. For example, if you take insulin just once daily, you only need 19 syringes if you take 50 units of insulin daily from that vial. Put the correct number of syringes needed in a box, cup, drawer, or other container. When you have used these syringes up, it’s time to start a new vial.
If your eyesight is poor, find more simple solutions for managing your medicines safely at the American Foundation for the Blind Senior Site.
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