Body weight

Body weight is the mass of a person or animal, and in pharmacology it is the most common basis for scaling how much of a substance the body receives.

Many drugs are prescribed in milligrams per kilogram because larger bodies have more blood volume and tissue to distribute a compound into, so the same absolute amount produces a lower concentration in a heavier individual. Fat-soluble compounds such as cannabinoids also accumulate in fat tissue, which means body composition, not only total weight, influences how long they persist and how quickly they clear. Veterinary prescribing relies on weight-based scaling almost universally because animals range from a few pounds to hundreds.

Clinical trial results are often reported in mg/kg, and the approved cannabidiol seizure medicine is prescribed that way. For consumer hemp products, body weight appears in general educational material about individual variability, but labels state serving sizes in milligrams rather than per kilogram, and no weight-based amount has been established for any nonprescription use.