Which type of insulin can be administered intravenously?

Humulin R, which is a form of regular insulin, is the type of insulin that can be administered intravenously. This is because regular insulin has a predictable and rapid onset of action, making it suitable for situations requiring tight control of blood glucose levels, such as in hospitalized patients or during surgery. The intravenous route allows for immediate effects and adjustments in dosing based on blood glucose monitoring.

The other types of insulin listed—Lantus, Novolog, and Levemir—are not typically used for intravenous administration. Lantus and Levemir are long-acting insulin formulations that provide a steady, prolonged release of insulin, designed for subcutaneous use and not for immediate correction of blood sugar. Novolog is a rapid-acting insulin meant for subcutaneous injections or insulin pumps, not for intravenous use due to its formulation and action profile. Thus, the correct answer acknowledges the specific suitability of Humulin R for intravenous delivery in a clinical setting.