What is a lethal dose chart?
A lethal dose chart compares how toxic different substances are using the LD50, the dose that kills half of a group of test animals, given in milligrams per kilogram of body weight. The lower the number, the more toxic the substance. Values run from more than 90,000 mg/kg for water to about 1 ng/kg for botulinum toxin, a gap of about 11 orders of magnitude [2].
The infographic by CEUfast, a nursing education provider, puts 55 everyday and not so everyday substances on one scale, from table sugar and caffeine to nerve agents and bacterial toxins [1]. It is a useful way to see how wide the range of toxicity is. It is not a guide to what would harm a person, and the reasons for that are covered below.
What LD50 means
LD stands for lethal dose. The Canadian Centre for Occupational Health and Safety (CCOHS) defines the LD50 as the amount of a material, given all at once, that causes the death of half of a group of test animals [3]. It measures acute toxicity, which is the harm a substance does soon after a single dose (within minutes, hours or up to about two weeks), not the effect of exposure over months or years [3].
The test was devised by the British pharmacologist J. W. Trevan in 1927 as a way to compare medicines that poison the body in very different ways, by using death as the common end point [2][3]. Most tests use rats or mice. The dose is given by mouth (oral), on the skin (dermal) or by injection, and a proper LD50 always states both the animal and the route, for example “LD50 (oral, rat) 5 mg/kg” [3].
The route matters a lot. CCOHS gives the insecticide dichlorvos an oral LD50 of 56 mg/kg in rats, 15 mg/kg when injected into the abdomen and 10 mg/kg by mouth in rabbits [3]. So two figures for the same substance can differ several times over without either being wrong.
Toxicologists also use a few related measures. LC50 is the lethal concentration in air or water, usually over a four hour exposure. LD01 and LD100 are the doses that kill 1% and 100% of the test group, LDLo is the lowest dose known to have caused a death, and TDLo is the lowest dose known to have caused a toxic effect [3].
LD50 values of common substances
These are median lethal doses for a selection of the substances on the CEUfast chart, with the animal and route each figure comes from, as listed in Wikipedia’s compiled table of published values (which the chart itself cites) [1][2]. One milligram (mg) is 1,000 micrograms (µg), and one microgram is 1,000 nanograms (ng).
| Substance | LD50 | Tested in |
|---|---|---|
| Water | more than 90,000 mg/kg | Rat, oral |
| Sucrose (table sugar) | 29,700 mg/kg | Rat, oral |
| Monosodium glutamate (MSG) | 16,600 mg/kg | Rat, oral |
| Vitamin C | 11,900 mg/kg | Rat, oral |
| Ethanol (alcohol) | 7,060 mg/kg | Rat, oral |
| Sodium chloride (salt) | 3,000 mg/kg | Rat, oral |
| Paracetamol (acetaminophen) | about 2,000 mg/kg | Rat, oral |
| THC | 1,270 mg/kg | Rat, oral |
| Methanol | 810 mg/kg | Human, oral (estimate) |
| Ibuprofen | 636 mg/kg | Rat, oral |
| Psilocybin | 280 mg/kg | Mouse, oral |
| Aspirin | 200 mg/kg | Rat, oral |
| Caffeine | 192 mg/kg | Rat, oral |
| MDMA | 160 mg/kg | Rat, oral |
| Cocaine | 96 mg/kg | Mouse, oral |
| Sodium fluoride | 52 mg/kg | Rat, oral |
| Capsaicin (chilli heat) | 47.2 mg/kg | Mouse, oral |
| Vitamin D3 | 37 mg/kg | Rat, oral |
| Heroin | 21.8 mg/kg | Mouse, intravenous |
| Arsenic trioxide | 14 mg/kg | Rat, oral |
| Sodium cyanide | 6.4 mg/kg | Rat, oral |
| Sarin (nerve agent) | 172 µg/kg | Mouse, injection under the skin |
| Fentanyl | 30 µg/kg | Monkey |
| Inland taipan venom | 25 µg/kg | Rat, injection under the skin |
| TCDD (dioxin in Agent Orange) | 20 µg/kg | Rat, oral |
| Polonium-210 | 10 ng/kg | Human, inhaled (estimate) |
| Botulinum toxin | 1 ng/kg | Human (estimate) |
A few figures on the CEUfast graphic differ from the published values, so the table above uses the corrected ones [2].
- Fentanyl is given as 300 µg/kg on the graphic. The published figure is 30 µg/kg, ten times lower.
- The 180 mg/kg figure labelled sodium nitrate (used in cured meat) is the value for sodium nitrite, a different curing salt.
- MDMA is printed as 160 mg/kg and 0.18 g/kg. 160 mg/kg is 0.16 g/kg.
- Arsenic is given as 13 mg/kg, which is metallic arsenic injected into the abdomen of rats. Swallowed elemental arsenic has an LD50 of 763 mg/kg in rats, while arsenic trioxide, the classic poison, is 14 mg/kg.
- Ricin’s 22 µg/kg is an injected dose. By mouth the figure in rats is 20 to 30 mg/kg, about a thousand times higher.
- Maitotoxin, from fish that cause ciguatera poisoning, is given as 130 ng/kg. The current published value is 50 ng/kg in mice.
- Nicotine is given as 0.8 mg/kg. That comes from an old human estimate of 0.5 to 1 mg/kg, which is covered in the section on people below.
Toxicity classes from relatively harmless to extremely toxic
Because LD50 values span such a huge range, toxicologists group them into classes. The Hodge and Sterner scale, one of the two most widely used, is based on a single oral dose in rats [3]. The examples are from the table above.
| Class | Oral LD50 in rats | Examples |
|---|---|---|
| Relatively harmless | 15,000 mg/kg or more | Water, sucrose, MSG |
| Practically non-toxic | 5,000 to 15,000 mg/kg | Vitamin C, ethanol |
| Slightly toxic | 500 to 5,000 mg/kg | Salt, paracetamol, ibuprofen |
| Moderately toxic | 50 to 500 mg/kg | Aspirin, caffeine, sodium fluoride |
| Highly toxic | 1 to 50 mg/kg | Vitamin D3, arsenic trioxide, sodium cyanide |
| Extremely toxic | 1 mg/kg or less | TCDD |
The other common scale (Gosselin, Smith and Hodge) uses different numbers and names, so the same substance can be “highly toxic” on one and “super toxic” on the other. CCOHS advises always saying which scale you are using [3].
The dose makes the poison
The oldest idea in toxicology, usually credited to the 16th century physician Paracelsus, is that everything is poisonous at a high enough dose and the amount is what decides whether something is harmful. A lethal dose chart shows this well, because the less toxic end is made up of things you eat and drink every day.
Water has the highest LD50 of anything listed, but drinking far too much in a short time can still kill by diluting the sodium in the blood (hyponatraemia). Salt itself is in the slightly toxic class. Vitamin D3 sits in the highly toxic class at 37 mg/kg in rats, which is why supplements are sold in microgram doses and why taking far more than the label says can cause harm [2].
Caffeine is a good example of a substance with a wide gap between normal use and harm. The US Food and Drug Administration cites 400 mg a day, about two to three 12 fl oz cups of coffee, as an amount not generally linked to negative effects for most adults, but it notes that sensitivity varies a lot between people and advises against energy drinks for children and teens [5].
Why animal figures don’t give a human lethal dose
Almost every value on a lethal dose chart comes from animal tests, and CEUfast’s graphic says as much [1]. Wikipedia’s article on the measure describes the LD50 as somewhat unreliable, because results vary between laboratories, animal strains, species and routes. It is also only the midpoint, so some animals in a test die at much lower doses and others survive far higher ones [2]. A few examples show why you can’t simply scale an animal figure up to a person.
- Species differ. Chocolate is harmless to people in normal amounts but toxic to dogs and many other animals, and many snake venoms are adapted to kill mice, so mouse tests can exaggerate how dangerous they are to humans [1][2].
- Paracetamol has a rat LD50 of about 2,000 mg/kg, which puts it in the slightly toxic class, yet it is one of the medicines the NHS names as a common cause of poisoning in people [2][4]. The rat figure says nothing about a safe dose for a person, so always follow the dose on the pack.
- Old human estimates can be wrong too. The long quoted lethal dose of nicotine (0.5 to 1 mg/kg, the basis of the graphic’s 0.8 mg/kg) was traced in a 2013 review in Archives of Toxicology to dubious self-experiments from the 19th century, and documented cases of people surviving much larger amounts suggest the real figure for adults is far higher [6]. Liquid nicotine for e-cigarettes is still dangerous, especially to young children, who can become seriously ill from small amounts.
When regulators turn animal results into exposure limits for people, they build in safety factors of 1,000 or 10,000 to allow for differences between individuals and the uncertainty in the tests [3]. The LD50 is also only one measure. It says nothing about the doses that cause serious but non-lethal harm, or about long term effects [3].
If you think someone has been poisoned
Don’t wait for symptoms, as some poisons take hours or days to show effects [4].
- In the US, call Poison Help on 1-800-222-1222 or use PoisonHelp.org. Call 911 if the person has collapsed, has trouble breathing or is having a seizure [7].
- In the UK, call 999 or go to A&E if you think someone has swallowed, touched or breathed in something harmful, has lost consciousness, is struggling to breathe or is having a seizure. Call NHS 111 if you’re not sure whether something is harmful [4].
- Don’t try to make the person sick and don’t give them anything to eat or drink. Take the packaging or container with you so doctors know what was taken [4].
If you are reading about lethal doses because you are thinking about harming yourself, please talk to someone now. In the US you can call or text 988 (the Suicide and Crisis Lifeline), and in the UK and Ireland you can call Samaritans free on 116 123, at any time [8][9].
Questions about lethal dose charts
What is the most toxic substance known?
Botulinum toxin, made by the bacterium Clostridium botulinum, is generally regarded as the most toxic substance known, with an estimated human LD50 of about 1 ng/kg [2]. The same toxin in tiny, controlled amounts is the active ingredient in Botox and several medical treatments.
What is the difference between a toxic dose and a lethal dose?
A toxic dose causes harm, such as organ damage, seizures or breathing problems, while a lethal dose causes death. Toxicologists measure the first with values such as TDLo (the lowest dose known to cause a toxic effect) and the second with LD50 or LDLo [3]. A toxic dose is always lower than a lethal one, which is why an LD50 is no guide to what is safe.
Is there an LD50 list for humans?
No proper one exists, because LD50 tests are not done on people. The few human figures in published tables, such as those for methanol, polonium-210 and botulinum toxin, are estimates from poisoning cases and animal data [2]. For medicines and chemicals, poison centres and the safety data sheet are the reliable sources.
What is the LD50 of caffeine?
The oral LD50 of caffeine in rats is 192 mg/kg, which puts it in the moderately toxic class [2][3]. Normal coffee drinking is far below the levels that cause harm, and the FDA cites 400 mg a day as generally fine for most adults [5]. The real risk is from pure and highly concentrated caffeine products. The FDA says toxic effects such as seizures can be seen after rapidly taking around 1,200 mg, which is less than half a teaspoon of pure caffeine powder [5].
Can you die from drinking too much water?
Yes, although it is rare. Drinking a very large amount in a short time can dilute the sodium in your blood to dangerous levels (water intoxication or hyponatraemia). Water still has the highest LD50 of any substance on the chart, at more than 90,000 mg/kg in rats [2].
Why is a lower LD50 more toxic?
Because the LD50 is the amount it takes to kill half the test animals. If a tiny amount does that, the substance is very toxic. If it takes a huge amount, it isn’t [3].
Sources
- CEUfast, The Lethal Doses of 55 Substances, September 2021 (archived copy, as the original post is no longer online).
- Wikipedia, Median lethal dose (table of published LD50 values with species, route and references).
- Canadian Centre for Occupational Health and Safety, What is a LD50 and LC50?
- NHS, Poisoning.
- US Food and Drug Administration, Spilling the Beans, How Much Caffeine is Too Much?
- Mayer B., How much nicotine kills a human? Tracing back the generally accepted lethal dose to dubious self-experiments in the nineteenth century, Archives of Toxicology 88, 5 to 7 (2014).
- America’s Poison Centers, Poison Help line 1-800-222-1222.
- 988 Suicide and Crisis Lifeline, 988lifeline.org.
- Samaritans, samaritans.org.
Last reviewed 10 November 2026
