Insulin, a hormone produced by the pancreas, helps regulate blood sugar (glucose) levels by moving glucose from the bloodstream into cells for energy or storage. In individuals with diabetes, the body either doesn’t produce enough insulin or can’t effectively use it, leading to high blood sugar. Managing these levels with manufactured insulin is fundamental to diabetes care, preventing serious complications.
Subcutaneous Administration: The Primary Method
Subcutaneous injection is the most common method for self-administering insulin. “Subcutaneous” refers to the fatty tissue layer just beneath the skin. Injecting insulin here allows for gradual, consistent absorption into the bloodstream. This method is preferred due to its simplicity for home use, promoting patient independence.
The fatty tissue provides a suitable environment for absorption, having a rich blood supply but few major vessels or nerves that could cause rapid absorption or significant pain. This slower, predictable absorption helps maintain stable blood sugar levels, making it the standard for routine insulin therapy.
Administering Subcutaneous Insulin
Proper technique is important for effective subcutaneous insulin administration. Always wash hands before injecting. If using an insulin pen, attach a new needle and prime it. For vials, draw air into the syringe, inject it into the vial, then draw the correct insulin dose.
Rotate injection sites to prevent hardened lumps (lipohypertrophy) that can interfere with absorption. Common sites include the abdomen (avoiding the navel area), thighs, upper arms, and buttocks. Rotate within an area, moving about an inch or two from the previous spot.
Clean the chosen site with an alcohol swab and let it dry. Pinch the skin, insert the needle at a 90-degree angle, and push the plunger. Hold the needle in place briefly to ensure full delivery, then withdraw. Dispose of the used needle immediately in a sharps container.
Other Insulin Delivery Methods
While subcutaneous injection is the primary method for routine insulin, other delivery methods exist for specific situations.
Intravenous (IV) Insulin
IV insulin is reserved for emergency or critical care, such as treating dangerously high blood sugar in diabetic ketoacidosis or during surgery. Administered directly into the bloodstream, IV insulin acts quickly, allowing precise, rapid adjustments under medical supervision.
Intramuscular (IM) Insulin
IM insulin delivers insulin into muscle tissue. Though it absorbs faster due to increased blood flow, it’s not recommended for routine self-administration. This is because it leads to more rapid, less predictable absorption, increasing low blood sugar risk. IM injections are also often more painful than subcutaneous ones.
Inhaled Insulin
Inhaled insulin is a needle-free alternative, where powdered insulin is breathed into the lungs via an inhaler. This method allows rapid absorption, typically working within minutes. Primarily used for mealtime insulin, it benefits those who prefer to avoid injections, but is unsuitable for people with certain lung conditions like asthma or COPD.
Insulin Pumps
Insulin pumps provide continuous delivery through a small catheter under the skin, changed every few days. These devices deliver small, continuous basal doses and allow users to program bolus doses for meals or to correct high blood sugar. Pumps offer increased lifestyle flexibility and can lead to more stable blood sugar control for some.
Factors Affecting Insulin Absorption
Several physiological factors influence how quickly subcutaneously injected insulin is absorbed.
Injection Site
The injection site plays a role, with insulin generally absorbing fastest from the abdomen, followed by the arms, then the thighs, and slowest from the buttocks. This difference is particularly relevant for rapid-acting insulins.
Physical Activity
Physical activity can also impact insulin absorption. Exercising a limb where insulin was injected shortly after injection increases blood flow, speeding up absorption. This accelerated absorption can lead to lower-than-desired blood sugar levels. Therefore, individuals are advised to avoid injecting into areas that will be heavily used during exercise.
Skin Temperature and Depth
Skin temperature at the injection site influences absorption; higher temperatures accelerate it, while colder temperatures slow it down. For instance, a hot bath or heating pad can increase absorption. The depth of injection also matters; injecting into muscle rather than subcutaneous fat leads to much faster, less predictable absorption, increasing low blood sugar risk.