An oral solution and an oral suspension are both forms of oral liquid medicines, but they differ in how the active ingredient is present. In an oral solution, the active pharmaceutical ingredient (API) is completely dissolved in the liquid vehicle, producing a uniform preparation. Because the drug is dissolved, the medicine generally does not require shaking before each dose. In an oral suspension, the active ingredient is not completely soluble in the liquid vehicle. Instead, fine solid particles are dispersed throughout the liquid and may gradually settle when the product is left standing. Therefore, an oral suspension usually needs to be shaken well before use to ensure the drug is evenly distributed and the correct dose is delivered. The choice between these types of liquid formulation depends on factors such as drug solubility, stability, taste, and the intended oral formulation. Thus, an oral solution is a dissolved and generally clear oral liquid, while a suspension contains dispersed solid particles.