An initial dose larger than the regular maintenance dose, administered to rapidly achieve therapeutic blood concentrations. Without a loading dose, a drug with a long half-life would take multiple regular doses (approximately five half-lives) to reach steady state.

Loading doses are common in clinical pharmacology—antibiotics, anticoagulants, and some biologics use them routinely. In the peptide community, loading dose protocols appear frequently in Melanotan II and BPC-157 discussions, though the evidence supporting specific loading protocols for most research peptides comes from community experience rather than controlled trials. The concept is pharmacologically sound; whether specific loading protocols are optimal for specific peptides is a different question.