Where Should Insulin Be Injected? A Practical Guide to Choosing and Rotating Injection Sites

The recommended sites are those that allow insulin to be administered into the layer of fat immediately beneath the skin: the abdomen, thighs, buttocks, and back of the upper arms. The thickness of subcutaneous tissue varies between individuals and between different areas of the body, so the choice of site should be adapted to each person’s build.

The abdomen provides a large surface area for rotation. The area between the ribs and the lower abdomen, including the sides, may be used, while avoiding the region immediately around the navel. As a practical rule, it is recommended to keep approximately 5 cm away from the navel.

The entire surface of the leg is not suitable for a thigh injection. The appropriate area is the front outer or outer part of the thigh, particularly the upper and middle thirds. Avoid the inner thigh, the area very close to the groin crease, and the area around the knee. The injection should be given where there is sufficient subcutaneous tissue, not directly into a very muscular area.

The upper arm may be used in the middle third of its back or back outer surface. Self-administration may be more difficult because positioning the pen and correctly forming a skinfold are not always easy. The buttocks may be used in the upper outer or back outer area, including toward the flanks.

A 4 mm needle is recommended for most children and adults, regardless of weight, because it allows the insulin to reach the subcutaneous tissue and reduces the risk of an intramuscular injection. The pen should be held perpendicular to the surface of the skin, at a 90° angle.

In general, adults do not need to form a skinfold when using a 4 mm needle. A skinfold may be necessary for young children, very thin individuals, when using longer needles (6 or 8 mm), or when the distance between the skin and muscle is small. The technique should be demonstrated individually by a doctor or nurse, especially if longer needles are used.

After inserting the needle, press the pen button down fully and keep the needle under the skin for approximately 10 seconds before withdrawing it. This pause reduces the risk of some insulin leaking onto the skin’s surface. The needle should be changed after every administration and discarded in a designated sharps container.

The skin should be checked before every injection. Do not inject into areas that are inflamed, infected, ulcerated, swollen, painful, or bruised. It is preferable to avoid scars and prominent stretch marks. Injecting through clothing is not recommended because the skin cannot be inspected properly.

Repeated injections into the same site can cause lipohypertrophy. This may be visible as a soft swelling or may feel like a denser, thickened, or “rubbery” area when touched. Patients sometimes prefer these sites because injections hurt less, but insulin absorption may become unpredictable, leading to fluctuations in blood glucose and unexplained episodes of hypoglycaemia or hyperglycaemia.

Rotation does not mean randomly choosing a different region for every dose. One simple method is to divide the abdomen into quadrants and the thighs, arms, or buttocks into halves. Use one area for approximately one week, placing each injection at least 1 cm away from the previous one, and then move systematically to the next area.

Injection sites should be inspected and palpated periodically. If an area suspected of lipohypertrophy is identified, insulin should no longer be administered there. Moving from altered tissue to healthy tissue may increase insulin absorption and contribute to hypoglycaemia. Blood glucose levels should therefore be monitored more closely, and doses should not be changed without advice from the medical team.

Movement can affect absorption from a limb. For example, injecting into the thigh before intense physical activity involving the legs may make the insulin’s effect less predictable. The choice of site should take into account the type of insulin, the timing of administration, and the planned activity.