分布体积（V_D），又称为拟似分布体积，是药理学的名词用作量化药物剂量服用后（不论是口服或是静脉注射）在体内的分布。它的定义是指一个药物剂量平均分布的体积，致使血液内的药物浓度达至可观察的程度。

分布体积在肾衰竭及肝衰竭的情况下，因体液的滞留及蛋白质结合而上升。相反，在脱水下分布体积亦会下降。

起始分布体积是描述在达至分布体积前的血液浓度，而它们都是使用同一方程序。

In pharmacology, the volume of distribution (V_D, also known as apparent volume of distribution) is the theoretical volume that would be necessary to contain the total amount of an administered drug at the same concentration that it is observed in the blood plasma. It is defined as the distribution of a medication between plasma and the rest of the body after oral or parenteral dosing.