We are pleased to present the last section of our three-part series on insulin sponsored by Viatris and written by Amy Hess Fischl, MS, RD, LDN, BC-ADM, CDCES. Content is provided for information only; please consult with your health care provider before making changes to your diabetes management.

In All About Insulin (Part One) and All About Insulin (Part Two), we covered the basics of insulin use, the types available, how it is administered, and some fundamental considerations to make the most of your insulin doses each day. Our final section will discuss site selection, rotation, and factors that affect glucose.

WHY IS SITE SELECTION AND ROTATION SO IMPORTANT?

Where you inject insulin matters because it affects how consistently insulin absorbs, which dictates its action, onset, and peak. Preferred areas to inject are:

• Stomach
• Thighs
• Top of the butt/upper hip
• Back of the arm

Figure: Site rotation sites from https://livingwithdiabetes.bd.com/successful-injections/site-rotation

The abdomen has the most consistent absorption and especially should be used when being very active with your arms and legs. More movement of those sites (and their muscles) may affect how quickly injected insulin is absorbed.

The risk of developing lipohypertrophy (lipo – also known as lumps and bumps at injection sites) increases with repeated injections into small areas that are less than the size of a quarter. Areas for injection should be at least the size of your entire hand, and each injection should be rotated within the area, spaced at least one finger width apart.

Bottom line: do not inject in the exact same spot each time or it could lead to absorption issues.

Lipo has also been associated with needle reuse. Injecting into an area of lipo can cause irregular insulin absorption and impact glucose levels – slower absorption and delayed peak effect are common side effects of using a site with lipo.

To reduce the risk of lipo, structured site rotation within the same area of the body is recommended. Structured rotation means rotating between and within site locations. Each injection should be at least 1-1/2” (the width of 1-2 fingers) from the last site. For example, if using the abdomen:

• Divide the abdomen injection area into four sections.
• Divide each area into smaller sections – use only one section each week.
• Rotate within that section with the next injection site 1-1/2” from the last site.
• Rotate to the next section the following week.
• Repeat weekly.
• It typically takes 20-30 days for an injected site to heal completely, meaning this time frame is a good rule of thumb to use before returning to a specific site location and reducing the risk of lipo.

Figure – from Forum for Injection Technique (http://fit4diabetes.com)

BRUISING AND BLEEDING AT THE INJECTION SITE

Local bleeding and bruising at an injection site may occur occasionally and do not affect insulin absorption. They also do not appear to be associated with the choice of your injection site. Bleeding does tend to be caused by using excessive force at the site. Not pressing too hard into the skin and using a thinner gauge needle have been shown to reduce the risk of bleeding.

Bottom line:

• To shrink the capillaries and help reduce the risk of bleeding at an injection site, you can use an ice pack for 30-60 seconds.
• Avoid indenting the skin while injecting; pushing the needle deeper than it needs to go increases the risk of accidentally injecting it into the muscle.
• Pregnant women giving injections can use all of the same sites. However, as the pregnancy progresses, the skin on the abdomen may become far more tight and uncomfortable to use as an injection location. The sides of the stomach may still be possible, provided the desired sites can be comfortably reached.
• For very thin individuals and small children, it will be necessary to pinch up a one- or two-inch amount of skin to ensure it is injected under the skin and not into the muscle.

FACTORS THAT AFFECT GLUCOSE

Numerous factors affect glucose levels and can be found in great detail here: https://diatribe.org/42-factors-affect-blood-glucose-surprising-update. Focusing on the types of insulin injected, timing of the dose, medication interaction, locations of the injection site, steroid administration, and niacin supplementation all can affect glucose levels.

INSULIN FACTS

• Over 7.4 million people in the United States use insulin.
• Insulin use in the United States varies by race and economic status: 14% of white people with diabetes use insulin, compared to 17% of Latinx people with diabetes and 20% of Black people with diabetes. 24% of people with diabetes who live below the poverty line use insulin.
• A single vial of insulin (1000 units) or a box of 5 insulin pens (1500 units) can cost over $400 without insurance.
• Although reforms are underway in many parts of the US, insulin costs are still prohibitively high for many people with diabetes. Reasons include the complexity of the pharmaceutical supply chain and the lack of generic substitutes. The American Diabetes Association (ADA) and Juvenile Diabetes Research Foundation (JDRF) have advocated for policy changes that would stop the trend of rising insulin costs and improve affordable access to insulin. Read the ADA policy statement on the issue here. And read the JDRF statement here.
• nability to afford insulin is the leading cause of diabetic ketoacidosis.

TYPE OF INSULIN USED MAY BE BASED ON YOUR INSURANCE PLAN

Insurance companies create contracts with pharmaceutical companies to get the best pricing for themselves and their plan participants. That means from year to year, it is possible the insulin you have been using may not be a preferred or cost-effective option for you any longer.

Generally speaking, switching within the same type of insulin (switching from a version of aspart to a version of lispro) should not have ANY impact on your glucose levels. However, there is always the possibility that there could be subtle differences. It may not be enough for your insurance company to cover it, though.

Bottom line: if your insurance plan changes you from one rapid-acting insulin to another, there usually is no danger in using your usual doses.

Reminder – there ARE insulin options that are available over-the-counter (without a prescription) – Regular (R) and NPH vials at Walmart (ReliOn) are <$30 per vial https://www.goodrx.com/healthcare-access/research/how-much-does-insulin-cost-compare-brands. IF you are in a pinch, cannot get in touch with your HCP office for an RX and to avoid DKA. HOWEVER, using R instead of rapid-acting, even for a short period of time, will have differing effects on glucose levels since it does not peak as quickly as rapid-acting insulin.

References:

1. Frid A, Kreugel G, Grassi G, et al. New insulin delivery recommendations. Mayo Clinic Proc 2016;91:1231–1255
2. Famulla, S. Hovelmann U, Fischer A. et al. Insulin Injection Into Lipohypertrophic Tissue: Blunted and More Variable Insulin Absorption and Action and Impaired Postprandial Glucose Control. Diabetes Care 2016;39:1486–1492
3. https://diatribe.org/42-factors-affect-blood-glucose-surprising-update
4. Cefalu WT, Dawes DE, Gavlak G et al. Insulin access and affordability working group: Conclusions and recommendations. Diabetes Care 2018;41:1299–1311 | https://doi.org/10.2337/dci18-0019
5. https://www.goodrx.com/healthcare-access/research/how-much-does-insulin- cost-compare-brands

Amy Hess Fischl, MS, RD, LDN, BC-ADM, CDCES, is an advanced practice dietitian and diabetes care and education specialist at the University of Chicago within the departments of pediatric and adult endocrinology. She speaks internationally on all diabetes topics, especially meal plan options for type 1 diabetes, insulin pumps, and continuous glucose monitors. She is actively involved in the American Diabetes Association, the Academy of Diabetes Care and Education Specialists, and the Academy of Nutrition and Dietetics, as well as several international groups for diabetes and pre-diabetes. She was named 2018 IL AADE Diabetes Educator of the Year and also received the 2018 Pan Arab Congress on Diabetes Award of Excellence for her contributions to diabetes care and education. Her dream vacation always includes diving with sharks.