LD50 (Lethal Dose, 50%) refers to the dose of a substance required to kill 50% of a tested population under controlled conditions. It is typically expressed in milligrams of the substance per kilogram of body weight (mg/kg) for the subject being tested, such as animals in laboratory studies.

Key Points:

1. Purpose: LD50 is used to measure and compare the acute toxicity of different substances.

2. Testing Population: The test is usually conducted on a specific group of animals, such as mice or rats, but extrapolation to humans must be done cautiously.

3. Route of Administration: The LD50 value depends on the route of exposure (e.g., oral, inhalation, dermal) because different routes may affect absorption and toxicity.

4. Units: LD50 is often reported in mg/kg, meaning the amount of substance (in milligrams) required per kilogram of the test subject’s body weight to reach the lethal 50% threshold.

Example:

• If the oral LD50 of a substance is 300 mg/kg, a dose of 300 mg would theoretically be lethal for 50% of a population of 1 kg animals.

LD50 values are a benchmark in toxicology for comparing substances’ toxic potency, though ethical considerations have reduced its use in favor of alternative testing methods.

Aspirin

LD50 200 mg/kg (rat, oral)

Gastric distress, confusion, psychosis, stupor, ringing in ears, drowsiness, hyperventilation

Sodium chloride (Salt)

12357 mg/kg (human, oral)

Eye irritant, elevated blood pressure

Glucose (sugar)

LD50 30 g/kg (rat, oral)

Depressed activity, gastrointestinal disturbances. If diabetic- heart disease, blindness, nerve damage, kidney damage
Ethanol (alchohol) 

LD50 7060 mg/kg (rat, oral)

Nausea, headache, vomiting, dizziness, nervous system depression, confusion, loss of consciousness

Caffeine

LD50 140 mg/kg (dog, oral)

Acute renal failure, nausea, psychosis, hemorrhage, increased pulse, convulsions