Diabetes mellitus, or diabetes, is increasing in prevalence worldwide. A common treatment for diabetes is injectable insulin.
Insulin tends to be prescribed to people who have had diabetes a long time, or who aren’t responding to other medications.
People typically inject insulin into the subcutaneous tissue of the abdomen. Still, it can also be injected into other areas with fat, such as the thighs and back of the arms.
Insulin can be injected in the form of an insulin pen, which is a convenient and newer form of insulin. Insulin pens use one-time use insulin needles that are screwed on to the end of the pen, which contains the medication.
Insulin is also available in vials. To inject insulin from a vial, a syringe is used, which contains a needle on the end. Needles are available in different gauges or thicknesses.
Some people wear insulin pumps, which continuously administer insulin through an infusion set worn under the skin.
While injecting insulin is safe, there are potential side effects from repeatedly injecting the skin. One of the possible side effects is lipohypertrophy.
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What is lipohypertrophy?
Lipohypertrophy is an abnormal accumulation of fat under the skin surface. This accumulation of fat occurs from the formation of scar tissue from repeated insulin injections.
Lipohypertrophy isn’t dangerous, but it can be uncomfortable. Injecting insulin into a spot with lipohypertrophy can cause the insulin not to be absorbed as well. This can lead to erratic blood glucose results.
What are the symptoms of lipohypertrophy?
Lipohypertrophy typically presents as a lump under the skin. The lumps can be small or large and can feel hard or rubbery in texture. They usually have a surface area over one inch in diameter. The lumps can occasionally present as soft masses, though they are usually hard.
A disorder of fat tissue similar to lipohypertrophy is lipoatrophy. Lipoatrophy tends to be associated with autoimmune disorders, such as type 1 diabetes and presents as a deep, retracted scar or lesion. Lipohypertrophy and lipoatrophy are both forms of lipodystrophy, which is the term for a disorder of fat, or adipose tissue.
People with lipohypertrophy tend to have higher blood glucose levels, as well as a higher frequency of unexplained hypoglycemia.
What causes lipohypertrophy?
Lipohypertrophy tends to occur as a result of injecting insulin into the same site over and over without rotating sites. When the same site is used for repeated injections, such as multiple insulin injections per day, scar tissue can form.
Lipohypertrophy can be diagnosed with a basic clinical examination with a healthcare provider. There usually aren’t any adverse events that occur as a result of lipohypertrophy.
However, if someone continues to inject insulin at the site affected by lipohypertrophy, the insulin treatment may not be absorbed as effectively or consistently. This can lead to erratic blood sugar readings.
What are the risk factors for lipohypertrophy?
Not rotating insulin injection sites is the leading risk factor for developing lipohypertrophy.
Using proper insulin injection techniques can reduce the risk. It’s recommended to inject insulin at least one inch away from the most recent site in order to prevent lipohypertrophy from occurring.
Insulin needles are meant to be used only one time and then disposed of. Reusing insulin needles can increase the chance of lipohypertrophy.
Even if the needle looks new, there can be dulling and bending that can’t be seen with the naked eye. Dull, bent needles are more likely to create skin injury and scarring and result in lipohypertrophy.
Some studies have also identified the following factors to be associated with lipohypertrophy:
- Female sex
- Low socioeconomic status
- High body mass index (BMI)
- Long-standing diagnosis of diabetes or prolonged insulin therapy
In one cross-sectional study of 174 patients with type 1 diabetes, nearly 46% of patients were found to reuse insulin needles, and around 43% didn’t rotate their insulin injection site.
Approximately 47% of the subjects in the study had lipohypertrophy. That same study found that people with uncontrolled diabetes were more likely to develop lipohypertrophy than people with controlled diabetes.
Another study found that lipohypertrophy occurred in as many as 62% of patients in a study group of 372 people with diabetes. That study found that being underweight may also be a risk factor for developing lipohypertrophy.
How can lipohypertrophy be prevented?
Lipohypertrophy is largely preventable by practicing proper insulin injection techniques. Proper insulin injection techniques include:
Using a fresh needle for every insulin injection. Re-using insulin needles increases the risk of developing lipohypertrophy. Insulin pens and insulin vials require new, single-use needles. If a person with diabetes is running out of insulin needles, they should speak with their healthcare provider about prescribing the right amount of needles to last between prescription refills.
Rotate the insulin injection site with every injection. It can be helpful to mark the spot where insulin was injected with a marker. This will remind the patient to pick a place at least one inch away from that spot the next time insulin is injected.
Rotating insulin injection sites will help the previous sites heal from the injections and be less likely to develop lipohypertrophy.
Use ideal insulin injection sites. The preferred insulin injection site is the abdomen, avoiding the area around the belly button.
For people with very little fat, such as thin individuals and children, the skin should be pinched together to provide enough fat for the needle to enter. Otherwise, there is a risk that the insulin will be injected into the muscle, not fat tissue, where it’s intended to be delivered.
Patients using insulin should receive education by a healthcare provider on proper insulin injection technique in order to reduce the risk factors for developing lipohypertrophy.
Unfortunately, many people prescribed insulin for the first time may not receive proper education on how to inject it in a way that can reduce the risk of complications.
Conclusion
Insulin injections are a conventional treatment for people with diabetes, primarily type 1 diabetes.
Insulin is injected into subcutaneous fat tissue where it’s absorbed into the body. The most common routes of insulin delivery include insulin pens, insulin vials, and syringes, and insulin pumps.
Lipohypertrophy is a form of lipodystrophy or a disorder of the adipose (fat) tissue. It occurs when scar tissue builds up to form a hard mass under the skin from repeated insulin injections.
The most common cause of lipohypertrophy is improper injection technique. Reusing an insulin syringe and not rotating injection sites are the main risk factors for developing lipohypertrophy in diabetic patients.
While lipohypertrophy isn’t necessarily dangerous, it can result in inconsistent or reduced absorption of the insulin dose. This can lead to erratic blood sugar readings, which could potentially be problematic.
The best way to prevent lipohypertrophy is to rotate the site of injection and use a new needle with every insulin injection. Patients taking insulin should be appropriately educated by healthcare providers on insulin injection technique. This will help to reduce the prevalence of lipohypertrophy.
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