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

According to the Centers for Disease Control and Prevention (CDC), over 80,000 drug overdose deaths occurred in the United States during 2024. 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.

This information should not be used to determine a safe drug dosage. If you suspect someone has overdosed, call 911 or your local poison control center right away. Getting prompt emergency medical attention is vital to saving someone’s life during a drug or alcohol overdose.

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:

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.

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 around 2 mg, approximately the amount that would fit on the head of a needle. This extremely dangerous substance is 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 molly (ecstasy/MDMA): about 2 grams (or 15-16 times the standard dose)
• fatal dose of LSD: 14 mg (about 140 times the standard dose)
• GHB: 14 to 20 mg (about 10 times the standard dose)
• lethal dose of ketamine: 4.2 grams (about 25 times the standard dose)
• PCP: 20 mg

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.

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Risk factors for prescription drug overdose:

• Mixing Prescription Drugs: Taking multiple prescription medications at the same time can cause dangerous interactions. Different drugs can amplify each other’s effects, leading to severe sedation, breathing problems, or heart complications. This is especially risky with combinations like opioids and benzodiazepines.
• Taking Higher Doses than Prescribed: Exceeding the recommended dosage can quickly lead to toxic levels in the body. Some people mistakenly think that if one pill helps, taking more will provide better relief, but this can result in life-threatening overdose symptoms.
• Taking Doses More Often Than Prescribed: Taking medication more frequently than directed can cause the drug to build up in your system faster than your body can process it. This accumulation increases the risk of reaching dangerous concentration levels.
• Crushing, Breaking, or Chewing Tablets: Many medications are designed as extended-release formulations that slowly release the drug over several hours. Crushing or chewing these pills releases the entire dose at once, which can cause a sudden, dangerous spike in drug levels.
• Drinking Alcohol While Taking Certain Drugs: Alcohol can intensify the effects of many prescription medications, particularly sedatives, pain relievers, and anxiety medications. This combination can severely depress the central nervous system, leading to slowed breathing and heart rate.

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:

• lethal dose of oxycodone (OxyContin): more than 40 mg (single) or 80 mg (total daily dose)
• hydrocodone (Vicodin) lethal dosage: more than 90 mg/day
• hydromorphone (Dilaudid) fatal dose: 3 to 10 mg
• oxymorphone: 172 mg/kg
• lethal dose of codeine: 0.5 to 1 g
• morphine fatal overdose: over 200 mg
• tramadol: >4000 mg
• methadone: 50 mg (for an opioid-naive adult)

In 2023, over 13,000 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:

• Xanax (alprazolam) fatal overdose: 4 mg
• Lethal dose of Ativan (lorazepam): 4 mg
• Klonopin (clonazepam) lethal dose: 20 mg
• Fatal dose of Restoril (temazepam): 30 mg
• Valium (diazepam) lethal dose: 40 mg

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:

• lethal dose of Luminal (phenobarbital)
• Lethal dose of Nembutal (pentobarbital)
• Seconal (secobarbital) lethal dose

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:

• lethal dose of Adderall (amphetamine): 1,400 mg
• Ritalin (methylphenidate) lethal dose: more than 60 mg
• lethal dose of Vyvanse: more than 70 mg

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:

• lethal dose of Wellbutrin (bupropion): 23,000 mg
• Ambien (zolpidem) lethal dose: 300 mg
• fatal dose of Seroquel: 6,000 mg
• lethal dose of Zoloft (sertraline): 2,500 mg
• gabapentin lethal dose: unknown (when taken alone)
• trazodone fatal dose: 6,450 mg

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. Below are some of the most common signs and symptoms of a drug overdose.

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

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.

How To Help Someone Overdosing On Drugs Or Alcohol

If you think someone is overdosing on drugs or alcohol, call 911 immediately. Don’t wait to see if they get better on their own. While waiting for help to arrive, try to keep the person awake and breathing by talking to them loudly or gently shaking their shoulders. If they’re unconscious, turn them on their side to prevent choking if they vomit. Check if they’re breathing regularly and look for signs such as blue lips, fingernails, or skin, which means they’re not getting enough oxygen. If you have naloxone (Narcan) and suspect an opioid overdose, use it right away by spraying it into their nose or injecting it into their muscle.

Stay with the person until emergency medical help arrives, and be ready to give rescue breathing or CPR if you know how. Don’t try to make them vomit, give them food or water, or put them in a cold shower. Tell the paramedics about what drugs or alcohol the person may have taken, even if the substances were illegal. Remember that Good Samaritan laws in most states protect people who call for help during an overdose, so don’t hesitate to get emergency assistance.

If you or a loved one is misusing drugs or alcohol, help is available. Reach out to your primary care provider or an addiction specialist for more information about substance use treatment programs.

Written by the Addiction Resource Editorial Staff