Lipohypertrophy is a lump of thickened tissue that can develop in the subcutaneous fat layer. It can be common in people who regularly receive subcutaneous injections for certain health conditions, such as diabetes.

The lumps are not tumors, and they are not malignant, but they may cause delays in the absorption of medication. Some people may also feel self-conscious about the appearance of the lumps.

However, prompt diagnosis and preventive steps will reduce the chance of lipohypertrophy recurring. In many cases, the lumps gradually disappear.

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Lipohypertrophy is the medical term for the abnormal growth of thickened skin tissue. It typically occurs when people get regular subcutaneous injections in the same area of skin — for example, when a person with diabetes gets regular insulin injections.

The lumps are not malignant. However, they may affect insulin absorption when a person injects that area of the skin. Inconsistent insulin absorption can result in either hypoglycemia (low blood sugar) or hyperglycemia (high blood sugar).

Some research suggests that the lumps may be at least partly due to the lipogenic effect of insulin rather than physical damage from needles.

Lipohypertrophy lumps may vary in size and appearance, although the main symptom is a raised area of skin, often in a frequently injected spot. Initially, lipohypertrophy may present as an area of slightly thicker skin that may be difficult to notice by sight or touch alone.

If it continues to grow, the lump may have a surface area of at least 1 inch in diameter, and it may feel more firm or dense than other areas of the skin. Although the affected area may be slightly uncomfortable, it is unlikely to cause noticeable pain.

However, if an infection is present, a person may experience some pain, as well as symptoms such as:

  • flushing or inflammation of the skin
  • the skin being hot or warm to the touch
  • an itching sensation
  • unusual bruising or bleeding

Anyone experiencing these symptoms should see their doctor as soon as possible in case they need treatment for an infection or another issue.

Several factors make lipohypertrophy more likely, including:

  • duration of insulin treatment
  • the person’s age and body mass index (BMI)
  • incorrect injections
  • using the same injection site each time rather than rotating several sites
  • the frequency of needle reuse

People with type 1 diabetes may develop lipohypertrophy because of the need for frequent injections or, possibly, as a reaction to insulin.

A 2020 study involving 1,227 people taking insulin for type 2 diabetes showed that structural changes in aging skin might put people older than 65 years at higher risk of developing the lumps.

The rotation of injection sites is an important modifiable risk factor for lipohypertrophy. A 2019 study that recruited 65 adults and 104 children with type 1 diabetes found that correct infusion and injection routines affect skin health and glycemic control.

A meta-analysis in the International Journal of Nursing Studies noted an increased risk of lipohypertrophy in people who reused the same needle for multiple injections. However, the varying results in each study meant that the authors could not use the data to make any definite recommendations. Also, the cost of extra needles may deter or prevent some people from changing this practice.

If lipohypertrophy causes visible lumps, their appearance may be sufficient for doctors to diagnose this condition.

However, a lipohypertrophy lump may sometimes be flat and not very visible, which means that a doctor may need to do a deep palpation examination or use a process such as ultrasonography to confirm a diagnosis.

Lipohypertrophy may reduce in size or disappear if the person rotates injections away from the area. Using a different area of skin for injections may also prevent inconsistent medicine absorption.

Doctors may also recommend medical or cosmetic treatments, such as steroids or liposuction, to remove any areas of thickened skin if a person finds their appearance bothersome.


The proper rotation of injection sites is an important preventive step. A person can consult with their doctor to learn about injection sites and areas that may be best for insulin injections.

Injection sites include the:

  • abdomen, away from the bellybutton
  • upper arm
  • upper buttock
  • thigh

Insulin enters the blood at different speeds from various injection sites, so the injection timing may need to vary. The American Diabetes Association notes that the body absorbs insulin fastest from the abdomen, less quickly from the arm, and slowest from the buttocks and thighs.

It is important to rotate injections within each injection site over an area the size of a postcard because restricting injections to a smaller area may increase the risk of lipohypertrophy. Research in Frontiers in Endocrinology found that people who rotated their injection site within an area the size of a credit card were 23.2 times more likely to develop lipohypertrophy than those who used a postcard-sized area.

Regular checks of common injection sites will help alert a person to early signs of lipohypertrophy, such as firmness or toughness under the skin. Reporting any skin abnormalities to a doctor may also help with early detection.

The raised bumps of skin from lipohypertrophy are not malignant, but they can interfere with how the body absorbs medicines, such as insulin. Also, some people dislike the appearance of these lumps on their body.

Prevention may include rotating both the injection site and the specific point of injection within each site. Anyone who thinks that they have lipohypertrophy should seek advice from their doctor on injection rotations or ask about using a different type of insulin, delivery system, or needle.