What is the name of a liquid dosage form that must be shaken well before use due to undissolved particles?

A liquid dosage form that requires shaking before use due to the presence of undissolved particles is known as a suspension. In a suspension, solid particles are dispersed throughout a liquid but are not dissolved, which means they settle over time if left undisturbed. Shaking the suspension redistributes the particles throughout the liquid, ensuring that each dose contains the appropriate amount of medication.

Emulsions, while they may also exhibit some instability, typically consist of two immiscible liquids (like oil and water) where one is dispersed as tiny droplets in the other and usually do not require shaking in the same way as suspensions. Creams are semi-solid emulsions and not liquids per se, and lozenges are solid forms intended to dissolve in the mouth, making them irrelevant in this context. Therefore, the characteristics of suspensions make them the correct answer for the question.