Glossary / Toxicology
LD50
LD50 is the statistically derived single dose of a substance, given by mouth or on the skin, that is expected to kill 50 percent of a group of test animals. It is expressed as milligrams of substance per kilogram of body weight.
Explanation
The test was developed as a standard way to compare how poisonous substances are. Lower LD50 values mean higher toxicity, because a smaller dose is enough to cause death. Because dose is scaled to body weight, mg/kg values can be compared across substances and, with care, across species.
The LD50 is the main basis for GHS oral and dermal acute toxicity categories. For oral toxicity, the Category 1 to 4 cutoffs are 5, 50, 300 and 2000 mg/kg. A substance with an oral LD50 at or below 5 mg/kg falls into Category 1, the most toxic group, and one above 2000 mg/kg is not placed in Categories 1 to 4. The matching hazard statements are H300, H301 and H302.
An LD50 has limits. It describes a single, short-term dose, says nothing about chronic effects, cancer or reproductive harm, and comes from animal tests under specific conditions. Species, sex, age and the way the substance was given all change the result, and results for people may differ. The SDS lists the species and route alongside the number.
For inhaled gases, vapors and dusts, the equivalent measure is the LC50, which uses concentration in air rather than a dose.
What to do and watch for
- Read the route and species with the number, because an LD50 for one route does not describe another.
- Use LD50 for relative comparison only, never as a safe dose.
- Rely on exposure limits and controls, not on LD50, to manage everyday exposure.
Where it appears on an SDS
- Section 11: Toxicological information. LD50 values with the test species and route, such as oral rat or dermal rabbit, are listed in the acute toxicity entry.
- Section 2: Hazard identification. The acute toxicity category assigned from the LD50 appears with its hazard statement and pictogram.
SDS content and wording vary by supplier. This page is general reference and does not replace the current SDS for your product.