Which type of insulin preparation has the fastest onset of action when administered subcutaneously?

Which type of insulin preparation has the fastest onset of action when administered subcutaneously?

• A. Glargine (Lantus)
• B. Lispro (Humalog)
• C. Regular (Humulin-R)
• D. NPH (Humulin-N)

Answer: (B)

The question tests how fast different insulin preparations begin to lower blood glucose after a subcutaneous injection. Rapid-acting insulins are formulated to be absorbed quickly from the injection site, so they start working sooner than regular or longer-acting forms. Lispro is a rapid-acting insulin analog designed to remain as monomers rather than forming hexamers, which speeds its absorption into the bloodstream. Because of this, lispro typically begins to act within about 15 minutes after injection, with a peak effect around 1–2 hours and a duration of roughly 3–5 hours. Regular insulin, while faster than some options, generally begins in about 30–60 minutes, peaks in 2–4 hours, and lasts 6–8 hours. NPH is an intermediate-acting formulation with onset around 2–4 hours and a longer, more variable duration. Glargine is long-acting, with onset typically 2–4 hours and no pronounced peak, lasting about 24 hours. Therefore, lispro has the fastest onset of action when given subcutaneously.

The question tests how fast different insulin preparations begin to lower blood glucose after a subcutaneous injection. Rapid-acting insulins are formulated to be absorbed quickly from the injection site, so they start working sooner than regular or longer-acting forms. Lispro is a rapid-acting insulin analog designed to remain as monomers rather than forming hexamers, which speeds its absorption into the bloodstream. Because of this, lispro typically begins to act within about 15 minutes after injection, with a peak effect around 1–2 hours and a duration of roughly 3–5 hours. Regular insulin, while faster than some options, generally begins in about 30–60 minutes, peaks in 2–4 hours, and lasts 6–8 hours. NPH is an intermediate-acting formulation with onset around 2–4 hours and a longer, more variable duration. Glargine is long-acting, with onset typically 2–4 hours and no pronounced peak, lasting about 24 hours. Therefore, lispro has the fastest onset of action when given subcutaneously.