Absorption Rate: Moderate, in between the abdomen and thighs.

Why: The arm has decent blood flow, though slightly less than the abdomen.

Common Use: Typically used for shorter-acting insulins, but rotation of all sites is important to avoid lipohypertrophy and maintain consistent absorption.

Absorption Rate: Fastest.

Why: The abdomen has a rich blood supply, allowing for quicker absorption.

Common Use: Often preferred for rapid-acting insulin due to its fast absorption.

Moderate to Slow: The side-torso or love handle area usually has a good layer of subcutaneous fat, which can slow down absorption compared to the abdomen but may be faster than the thighs or buttocks, depending on the person.

Why: Like other injection sites, the side-torso has subcutaneous fat, but blood flow to this area tends to be lower than the abdomen, leading to a slower absorption rate. However, it is still within the range for consistent insulin delivery, especially if you rotate injection sites regularly.

Suitability for Insulin Types:

Intermediate to Long-Acting Insulin: Due to the moderate-to-slow absorption rate, the side-torso might be suitable for longer-acting insulins (like NPH or basal insulins such as glargine or detemir) where a slower, more sustained absorption is desired.

Short-Acting Insulin: If using rapid-acting insulin in this area, the onset might be slightly slower compared to injecting in the abdomen, so timing adjustments might be needed.

Absorption Rate: Moderate to slow.

Why: The lower back or flank area generally has a good layer of subcutaneous fat, but blood flow is lower compared to areas like the abdomen. This results in a slower and more gradual absorption of insulin. It's similar to the thighs or buttocks, making it suitable for longer-acting insulins that need to be absorbed steadily over time.

Suitability for Insulin Types:

Best for Intermediate or Long-Acting Insulins: The moderate-to-slow absorption makes the lower back area ideal for basal (long-acting) or intermediate-acting insulins, where a gradual release over 12 to 24 hours is desired.

Less Ideal for Rapid-Acting Insulins: Due to slower absorption, rapid-acting insulin might not act as quickly as needed to manage post-meal blood sugar spikes.

Absorption Rate: Slow, similar to or slightly slower than the thighs.

Why: The buttocks have a thicker layer of subcutaneous tissue, which slows absorption.

Common Use: Suitable for longer-acting insulins.

Absorption Rate: Slower than the abdomen.

Why: The subcutaneous tissue in the thighs has less blood flow compared to the abdomen.

Common Use: This site is often used for long-acting insulin because the slower absorption is ideal for prolonged release.

Activity Level: Physical activity involving the arm, such as exercise, can increase blood flow and speed up absorption.

Depth of Injection: The accuracy of injecting into the subcutaneous fat (not too deep into the muscle) ensures proper absorption.

Skin Condition: Lipohypertrophy (fatty lumps) from repeated injections at the same spot can slow absorption, which is why rotating injection sites is important.

1. Rapid-Acting Insulin (e.g., Lispro, Aspart)

• Preferred Injection Site: Abdomen.
• Why: The abdomen provides the fastest absorption rate, which is ideal for rapid-acting insulins designed to quickly lower blood glucose after meals.
• Other Possible Sites: Upper arms can also be used, though absorption may be slightly slower compared to the abdomen.

2. Short-Acting (Regular) Insulin

• Preferred Injection Site: Abdomen.
• Why: Like rapid-acting insulin, short-acting insulin benefits from faster absorption for better blood sugar control around meals.
• Other Possible Sites: Upper arms are also a reasonable option but may slow the onset slightly.

3. Intermediate-Acting Insulin (e.g., NPH)

• Preferred Injection Sites: Thighs or buttocks.
• Why: These sites have slower absorption, which suits the delayed onset and prolonged effect of intermediate-acting insulin. A slower absorption helps smooth out insulin levels over a longer period, reducing the risk of hypoglycemia between meals.
• Other Possible Sites: Side torso (love handle area) or upper arms, though these may still have moderate absorption.

4. Long-Acting Insulin (e.g., Glargine, Detemir, Degludec)

• Preferred Injection Sites: Thighs, buttocks, or side torso.
• Why: Long-acting insulins are designed to provide a slow, steady release over 24+ hours, so injecting into sites with slower absorption helps maintain this consistency.
• Other Possible Sites: Upper arms or abdomen, though the abdomen may speed absorption more than desired, leading to less predictable effects.

5. Pre-mixed Insulin (e.g., 70/30, 50/50)

• Preferred Injection Sites: Thighs or buttocks.
• Why: Pre-mixed insulin contains both rapid- or short-acting and intermediate-acting components. The slower absorption from these sites helps with the long-lasting component, while still allowing for an initial insulin response.
• Other Possible Sites: Side torso or upper arms can also work, but faster sites like the abdomen should generally be avoided unless specifically advised by a healthcare provider.