Good Insulin Injection Practices

Good injection practices – such as proper injection technique, site rotation, and appropriate needle use – are as important to your glucose control as your type and dosage of insulin (1). But over time, you may have developed your own injection technique, which may not exactly accord with professional guidelines and standards.  For instance, you might reuse your needles. It’s a very common practice, despite the fact that guidelines issued by regulatory agencies call for all insulin injection needles to be labeled single-use only. However, changes to injection technique can alter insulin absorption and may lead to problems down the road.  So maybe it’s time for a refresher in the official line on appropriate insulin injection practices – injection technique, site rotation, and proper needle use (2).

Injection technique.  For the most efficient absorption and utilization, insulin should be injected into subcutaneous fat . Injected too deeply, the insulin could enter into the muscle, accelerating absorption and increasing the risk of hypoglycemia. If the injection is not deep enough, the insulin may leak out, reducing its effectiveness. Your mass index (BMI), along with the part of your body being injected and the length of your needle, determine the angle of injection.  A 90 degree angle is appropriate for areas of the body with more fat. To avoid injecting insulin into muscle, a less than 45 degree angle is better in areas of the body with less fat. You should pinch up a fold of skin to insert the needle at the appropriate angle.  If you are using a 5 millimeter mini-pen needle, however, no pinch-up is necessary because the shorter needle cannot reach the muscle (3).

Site selection and rotation.  Site selection is based on the different rates of insulin absorption.  The optimal – most predictable – area for injection is in the abdomen, followed by the outer back areas of arms, the outer thighs, and the buttocks.  The skin within a two-inch radius of the umbilicus should be avoided.  It is also important not to nject in areas to be exercised, because increasing blood flow can increase the rate of absorption (4).

Site rotation is important to prevent scar tissue, hard lumps, or fat deposits that may develop over time.  If you have encountered these problems, you may be tempted to continue to inject in lumpy nodules because such areas may be less painful.  These same areas, however, may cause erratic or unpredictable insulin absorption (5).

Proper needle use.  Insulin injection syringes and pen needles are sterile products, and guidelines issued by regulatory agencies call for all insulin injection syringes and pen needles to be labeled single-use only.  Although most insurance plans cover the required number of insulin pen needles and insulin syringes, many people reuse needles for reasons of thrift or convenience (6). Unfortunately, a reused needle may not inject as easily or as cleanly as a new needle, causing pain, bleeding, and bruising (7).  In addition, studies have shown that a link may exist between needle reuse and the appearance of lumps of fatty tissue that can form at the injection site.

Potential Risks of Needle Reuse

Although most insulin preparations have bacteriostatic additives that inhibit growth of the bacteria commonly found on the skin, needle reuse may carry an increased risk of infection for certain individuals.  According to the American Diabetes Association, it’s especially important that patients with acute concurrent illness, poor personal hygiene, open wounds on the hands, or a weakened immune system do not reuse insulin needles (8).

As single-use products, insulin needles are guaranteed sterile for one use only. A potential issue with needle reuse is the inability to guarantee sterility.  A study that examined insulin pens and insulin needles after injection found that 30 percent of the needles had biological material clinging to them, while 58 percent of the pens had biological matter (9). If you have suspected that this occurs, you probably clean your needle with alcohol before reuse.  Unfortunately, this removes the silicone lubricant added to the needle during manufacturing to help it pass smoothly through the skin (10).

Damage to needle, resulting in micro-trauma  

To increase comfort, the width of the needle has been made smaller, requiring the walls of the needle to be thinner. These thinner walls are strong enough for single-use, but not for repeated use.  A reused needle does not inject as easily or as cleanly as a new needle and can cause pain, bleeding, and bruising.  The tip of a reused needle can even be weakened to the point that it breaks off under the skin (11).

Dose Accuracy

The American Diabetes Association’s Resource Guide recommends that insulin pen needles should always be removed immediately after use. When left in place, the pen needle creates an open passage to the insulin chamber. The open passage may create air bubbles in the cartridge, which could trap some of the insulin and impact dosage (12). In addition, when the insulin pen needle is left on the insulin pen, it can be exposed to alterations in temperature. Insulin can contract when taken from a warm to cool environment, drawing air into the cartridge through the attached needle. Studies show that when there is added air in the insulin cartridge, the dose delivered is very inaccurate, and up to two-thirds of the required insulin may not be delivered. Conversely, insulin expands when taken from a cool to a warm environment.  This can cause the insulin to leak out, changing the concentration and strength of insulin remaining in the cartridge (13).

Increased formation of lipohypertrophy

Over time, some patients who inject insulin develop lipohypertrophy, which is soft, often grape-like lumps that appear at injection sites.  A study published in Diabetes Research and Clinical Practice reported on the incidence of lipohypertrophy in patients with diabetes.  This study, which was conducted in Europe where needle reuse is common, reported an incidence of lipohypertrophy between 27.1 and 48 percent in patients with type 1 diabetes and between 28 and 57 percent in patients with either type 1 or type 2 diabetes (14). Factors influencing lipohypertrophy development in these patients included the amount of time insulin had been used; the number of daily injections; gender; body mass index; injection sites; rotation of sites; the use of insulin pens only as opposed to syringes; needle length; and the frequency with which needles were changed (15).

Considering the period of lipohypertrophy development, patients who had been injecting insulin for at least two years were included in the research.  This study found the incidence of lipohypertrophy occurred in 20 percent of people with diabetes who changed their needle at every injection, in 51.2 percent of those who changed it every two or three injections, and in 75 percent of those who changed every four or five injections (16).

In summary, the fundamentals of good insulin injection practices, such as injection technique, site rotation, and proper needle use, will make it more likely that you will not experience pain or encounter other problems associated with your injections.

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1.  Strauss K, De Gols H, Letondeur C, Matyjaszcyk M, Frid A, The Second Injection Technique Event (SITE, May 2000, Barcelona Span), in Practical Diabetes International, John Wiley & Sons, Ltd., January 2002, Vol. 19, No. 1.

2. Strauss, et al, ibid.

3. Improving your injection technique, retrieved at:

4. American Diabetes Association, Insulin Administration, retrieved at:

5. American Diabetes Association, Insulin Administration, ibid.

6. 2008 Roper U.S. Diabetes Patient Market Study

7.  Risks of Needle Reuse, retrieved at:

8. American Diabetes Association, Insulin Administration, ibid.

9.  LeFloch, JP et al, Biological Material in Needles and Cartridges After Insulin Injection With a Pen in Diabetic Patients, Diabetes Care, 1998, 21(9): 1502-1504.

10. American Diabetes Association, Insulin Administration, ibid.

11. Risks of Needle Reuse, ibid.

12. American Diabetes Association, Insulin Delivery, Diabetes Forecast 2008 Resource Guide

13. Ginsberg BH, Parkes JL, Sparacino C:  The kenetics of insulin administration by insulin pens, Hormone and Metabolic Research  (1994) 26:584-587

14. Bahar Vardar, Sevgi Kizilci, “Incidence of lipodystrophy in diabetic patients and a study of influencing factors, Diabetes Research and Clinical Practice 77 (2007) 231-236

15. Vardar et al, ibid.

16. Vadar et al, ibid.

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