In toxicology, the lowest published toxic dose (Toxic Dose Low, TD<sub>Lo</sub>) is the lowest dosage per unit of bodyweight (typically stated in milligrams per kilogram) of a substance known to have produced signs of toxicity in a particular animal species. When quoting a TD<sub>Lo</sub>, the particular species and method of administration (e.g. ingested, inhaled, intravenous) are typically stated.
The TD<sub>Lo</sub> is different from the LD<sub>50</sub> (lethal dose) which is the dose causing death in 50% of people who are exposed or who consume the substance.