Lethal Doses Of Drugs: How Much Does It Take To Cause A Fatal Overdose?

Medically Reviewed by Johnelle Smith, M.D. on August 1, 2023

Taking very high doses of a drug, including alcohol, can be deadly without medical treatment. Here you will find the lethal dose for some of the most commonly misused drugs, including illicit, prescription, and over-the-counter drugs.

Lethal Doses Of Drugs

According to the Centers for Disease Control and Prevention (CDC), about 107,000 drug overdose deaths occurred in the United States during 2022.

Overdose can occur when someone takes too much of one or more drugs at once. This can overwhelm the body and cause organ failure, cardiac arrest, stopped breathing, and death.

Here you’ll find information on estimated lethal doses of commonly used illicit drugs, prescription drugs, and over-the-counter drugs. These are average estimates.

This information should not be used to determine a safe drug dosage. If you suspect someone has overdosed, call 9-1-1 or your local poison control center right away.

How Dosing Is Determined: Terms To Understand

When searching for safe or unsafe drug dosages, there are certain terms that may be helpful to understand.

Potent: The term ‘potent’ or potency refers to the strength of the drug.

Milligram (mg): Many drugs are prescribed or taken by the milligram (mg). One milligram is equal to 1/1000 of a gram.

Gram: Some drugs are dosed by the gram. One gram is equal to 1000 milligrams (mg) or about 0.035 of one ounce (oz).

Opioid tolerant: This is a term used to refer to people who are receiving at least 60 mg morphine/day, 25 mcg transdermal fentanyl/hr, 30 mg oxycodone/day, or 8 mg oral hydromorphone/day.

Factors That Can Affect Fatal Doses Of Drugs

The lethal dose for a given drug may not be the same for everyone. While lethal dosage amounts on this page are average estimates, a number of factors may affect this.

Factors that can influence lethal doses include:


Children and the elderly can fatally overdose on drugs after taking smaller doses.


People who are of a lower weight may overdose after taking smaller doses.

Drug Tolerance

People who have developed a tolerance to a drug may not experience fatal consequences after taking the average lethal dose.

History Of Drug Use

Having a history of drug use, especially substance misuse, may affect lethal dosages.

Medical History

Having poor health or certain health conditions may affect how much of a drug it takes to fatally overdose.

Use Of Multiple Drugs

Some drugs are not lethal on their own. Taking a drug with other drugs may increase the risk of fatal overdose (e.g. opioids with benzodiazepines).

Purity Level

Illicit drugs can vary in their level of purity. This can affect fatal overdose potential.

Route Of Administration

Injection drug use is associated with a higher risk of fatal overdose compared to swallowing or snorting some drugs.

This information should not be used to determine a safe drug dosage. Drugs can be lethal for some people in lower doses than they are for others.

Talk to your doctor if you’re concerned about how much of a drug you or a loved one is taking.

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Lethal Doses Of Illicit Drugs

Illicit drugs are those that are illegal to buy, sell, possess, or use. These drugs can be highly addictive and have limited or no acceptable medical use in the United States.

The legal status of some drugs, like marijuana, can vary by state. Laws regarding the possession or use of some illicit drugs can also vary depending on where you live.

Commonly used illicit drugs include:

  • cocaine
  • heroin
  • methamphetamine
  • illicit fentanyl
  • hallucinogens
  • inhalants
  • marijuana (legal in some states)

Identifying the lethal dose of illicit drugs is challenging. These drugs are commonly cut with other drugs, fillers, or additives, which can affect the lethal potential.

Here are the estimated lethal doses of the most commonly used illegal drugs.

Lethal Dose Of Cocaine

Cocaine is a powerful stimulant that can be lethal in doses exceeding 1.2 g, on average. In people with high sensitivity to cocaine, fatal overdose may occur with doses over 30 mg.

People who use cocaine regularly and in high doses may have a higher tolerance for cocaine. This means a fatal dose for them may be higher than for the average person.

Read more about the lethal dose of cocaine.

Lethal Dose Of Methamphetamine

Methamphetamine (meth) is an addictive stimulant. The estimated lethal dose of methamphetamine is about 200 mg, or 0.15 to 0.2 g.

Read more about the lethal dose of meth.

Lethal Dose Of Heroin

Heroin is an illicit opioid drug. It is commonly cut with other substances, which can affect its purity and lethal dosage.

The estimated lethal dose of heroin ranges from 30 mg to 500 mg, or 0.03 to 0.5 g.

This can vary depending on body composition, tolerance, method of use, and the use of other drugs with heroin. Heroin is sometimes cut with fentanyl, which can increase the overdose risk.

Read more about the lethal dose of heroin.

Lethal Dose Of Fentanyl

Fentanyl is a highly potent synthetic opioid. In recent years, illicitly manufactured forms of fentanyl have been the primary driver of drug overdose deaths across the U.S.

The estimated lethal dose of fentanyl is 2 mg. Depending on where the fentanyl comes from (i.e. illicit or prescription), the lethal dose may be lower.

Learn more about the lethal dose of fentanyl.

Lethal Dose Of Carfentanil

The lethal dose of carfentanil, an illegal fentanyl analog, is uncertain. However, it’s believed to be up to 100 times more potent than fentanyl and 10,000 times more potent than morphine.

Learn more about the lethal dose of carfentanil.

Lethal Dose Of Hallucinogens

Hallucinogens are a class of drugs that can affect the senses and perception. Hallucinogens are generally used for recreational purposes. They are also being studied for therapeutic use.

Some hallucinogens can be toxic when taken in very high doses or with other drugs.

Lethal doses of hallucinogens:

Lethal Dose Of THC

Tetrahydrocannabinol (THC) is the active ingredient in cannabis, also known as marijuana, pot, or weed. Marijuana is considered one of the least toxic of all recreational drugs.

According to the World Health Organization (WHO), the lethal dose for THC is an estimated 4 g in a 154-pound human.

This dose is unlikely to be realistically achieved by swallowing, vaping, or smoking the drug due to marijuana’s high margin of safety.

Read more about the lethal dose of marijuana.

Lethal Doses Of Prescription Drugs

Prescription drugs are generally safe and effective when taken as prescribed. Taking high doses of certain medications, or taking them in any way other than prescribed, can risk overdose.

Risk factors for prescription drug overdose:

  • mixing prescription drugs
  • taking higher doses than prescribed
  • taking doses more often
  • crushing, breaking, or chewing tablets
  • drinking alcohol while taking certain drugs

Note: Children, older adults, and people with certain health conditions can overdose on smaller doses than average.

Lethal Doses Of Prescription Opioids

Prescription opioids are primarily used to treat pain. However, they can also be highly toxic when taken in high doses or when used in any way other than prescribed.

Note: High doses of prescription opioids may be prescribed for opioid-tolerant patients. People who are opioid-tolerant may not die from doses deemed lethal for the average person.

Potentially fatal doses of common prescription opioids:

In 2019, over 14,000 drug overdose deaths involved prescription opioids. The lethal dose for prescription opioids can vary, depending on the type of opioid and the formulation.

There is a heightened risk of fatal overdose in people who are prescribed a high dosage or receive a high number of prescriptions.

Lethal Doses Of Benzodiazepines

Benzodiazepines, or “benzos,” are commonly prescribed for anxiety, panic, and seizures. Fatal overdose is not common from taking benzodiazepines alone.

Taking benzodiazepines with high doses of other depressants, such as opioids or alcohol, can lead to fatal consequences. Alone, a person would need to ingest thousands of milligrams.

Recommended daily limits of benzodiazepines:

Lethal Doses Of Barbiturates

Barbiturates are a class of powerful sedatives. In adults, as little as one gram of a barbiturate drug can be toxic. A lethal dose can range from 2 to 10 grams in adults.

Common barbiturate drugs include:

Taking barbiturates with other central nervous system (CNS) depressants can be fatal in smaller doses. Do not take barbiturates with alcohol, opioids, or other depressants without talking to a doctor.

Lethal Doses Of Prescription Stimulants

Prescription stimulants like Adderall are sometimes misused for their effects. Taking too much amphetamine may result in overdose.

Prescription stimulant overdose is rarely fatal. The risk of a fatal overdose can be higher in those who take amphetamines with high doses of other drugs.

Toxic doses of prescription stimulants:

People who have a high tolerance for amphetamines may take a lethal dose without fatal consequences. This can vary based on a person’s sensitivity to stimulants.

Lethal Doses Of Other Prescription Medications

A number of other various prescription medications are sometimes misused. When taken in high quantities, or mixed with other drugs, they may have toxic effects. Severe cases may be fatal.

Lethal doses of other prescription medications:

The drugs listed above are unlikely to cause fatal overdose when taken alone. Combined with other drugs, such as alcohol or opioids, these drugs may become lethally toxic in high doses.

Lethal Doses Of Non-Prescribed Substances

There are several drugs that are not typically prescribed, but can be acquired over the counter or at a typical drugstore. Taking excessive doses of these drugs, including alcohol, can be fatal.

Lethal Dose Of Alcohol

Alcohol can be toxic if drunk in excessive quantities. This can lead to alcohol poisoning or death. The lethal dose of alcohol is about 330 grams in a 154-pound, healthy adult.

This is equal to:

  • >30 standard drinks
  • one liter of spirits
  • four bottles of wine

The lethal amount of alcohol for children is about half the average amount for adults.

Read more about the lethal dose of alcohol.

Lethal Dose Of Caffeine

Drinking caffeinated products is unlikely to have severely toxic effects in the average person. However, the estimated lethal dose for caffeine is about 10 grams.

For comparison, a cup of coffee has about 100 to 200 milligrams. An energy drink contains up to 300 milligrams.

This means a person would have to drink 50 cups of coffee or 30 energy drinks very rapidly for there to be potentially fatal consequences.

Learn more about the lethal dose of caffeine.

Lethal Dose Of Melatonin

There is no evidence to suggest that taking excessive doses of melatonin can be fatal.

Studies have shown that taking up to 800 mg/kg in humans did not lead to fatal outcomes. No lethal dose of melatonin has been established.

However, a person can still overdose on melatonin and experience side effects.

Read more about the lethal dose of melatonin.

Lethal Dose Of Benadryl

Benadryl (diphenhydramine) is an over-the-counter medication commonly used for allergy-relief.

The estimated lethal dose of Benadryl is 1,400 mg to 2,800 mg in a 154-pound human.

This is equal to about 56 to 112 tablets. The lethal dose may be smaller in children and older adults.

Read more about the lethal dose of Benadryl (diphenhydramine).

Lethal Dose Of Acetaminophen (Tylenol)

Acetaminophen is the active ingredient in Tylenol, an over-the-counter painkiller. According to some estimates, the lethal dose of acetaminophen in adults is approximately 7,500 to 10,000 mg.

What Happens If You Take A Lethal Dose Of A Drug?

Taking lethal doses of a drug, including those prescribed by a doctor, can be deadly. If you suspect someone you know has taken a lethal dose of a drug, call 9-1-1 right away.

Common signs of drug overdose include:

  • slow, shallow, or stopped breathing
  • chest pain
  • unconsciousness
  • bluish lips or fingernails
  • changes in pupil size
  • very weak pulse
  • low blood pressure
  • very low or high body temperature
  • clammy or sweaty skin
  • nausea and vomiting
  • mental confusion
  • gurgling noises

Signs of an overdose vary depending on the type of drug taken. Not all overdoses are fatal.

The vast majority of overdoses in the United States each year are non-fatal. Non-fatal overdose may result in temporary or permanent health consequences.

Find Help For Drug And Alcohol Addiction Today

If you or a loved one is misusing drugs or alcohol, help is available. Call AddictionResource.net to learn more about treatment options such as detox, inpatient rehab, and outpatient rehab.

This page does not provide medical advice. See more

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These include peer-reviewed journals, government entities and academic institutions, and leaders in addiction healthcare and advocacy. Learn more about how we safeguard our content by viewing our editorial policy.

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Medically Reviewed by
Johnelle Smith, M.D. on August 1, 2023
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