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What causes overdose? Diagnosis, prevention, and treatment

Medically reviewed by Anne Jacobson, MD, MPH
Board-Certified Family Physician
Updated Feb. 1, 2024  •  Published Feb. 1, 2024
Fact Checked
What causes overdose? Diagnosis, prevention, and treatment

Overview: What is overdose?

All medications have potential benefits, but most can make people seriously sick if too much is taken, including vitamins and herbal remedies. Unfortunately, the symptoms of a drug overdose aren’t universal. They are often unique to the drug being taken. Some types of drug overdose, like opioid overdose, have signs that are immediate, dramatic, and obvious. Other overdoses may not look like an overdose. Acetaminophen is the most common cause of drug overdose in the U.S., but the symptoms may not look like a drug overdose, more like an illness. That’s because an acetaminophen overdose damages the liver. It doesn’t cause rapid loss of consciousness like an opioid overdose. Sometimes, the symptoms of an overdose may be subtle. Finally, for some drugs, such as aspirin, vitamins, or mineral supplements, it may take weeks or months of daily overdoses before the body is poisoned enough to start showing symptoms. Though the symptoms of drug overdose may vary by drug, healthcare professionals believe that most drug overdoses require emergency help or medical advice.

Key takeaways:

  • Overdose is a common health condition that can affect anyone regardless of age, sex, race, or ethnicity. 

  • Overdose is caused by substance abuse, self-harm, self-medication, medication errors, and medication accidents. 

  • Risk factors for overdose include illicit substance use, prescription drug abuse, mental health problems, use of multiple drugs, age, sensitivity to a drug due to medical conditions, and easy access to medications.

  • Symptoms of overdose may include nausea, vomiting, abdominal pain, diarrhea, chest pain, clammy skin, gurgling sounds, mental changes, emotional changes, increased or decreased alertness, increased or decreased energy, breathing changes, heart rate changes, body temperature changes, skin changes, and blood pressure changes.

  • Overdose usually requires a medical diagnosis and should be considered a medical emergency.

  • Overdose generally does require treatment. It typically resolves within a day or two, depending on the substance or substances that have been overdosed.

  • Treatment of overdose may include resuscitation, antidotes, activated charcoal, gastric emptying procedures, reversing agents, and dialysis. 

  • Overdose is preventable by substance abuse treatment, mental health treatment, safe medication use, proper medication storage, and medication management tools.

  • Use coupons for overdose treatments like Narcan (naloxone) to save up to 80%.

What causes overdose?

Drug overdoses have many causes. Most are due to decisions people make or actions people take. For this reason, overdoses are preventable.

  • Substance abuse: The most common causes of severe drug overdoses and overdose deaths in the United States involve illicitly used drugs, including opioids like oxycodone, alcohol, benzodiazepines like Valium (diazepam), and stimulants.

  • Self-harm: Suicide and suicide attempts are common causes of drug overdose and can involve drugs such as opioids, benzodiazepines, antidepressants, and even over-the-counter pain medications.

  • Self-medication: Self-medication—people making their own decisions about taking or dosing medications—is a significant public health problem that can involve misuse or overdose of prescription medications, over-the-counter drugs, dietary supplements, and herbal remedies. For instance, acetaminophen overdose brings over 50,000 people a year to the emergency room and kills 500 people a year. Half of these overdoses are people who are overmedicating to treat pain or other problems. 

  • Medication errors: Medication errors involve a constellation of mistakes that can lead to an overdose. Healthcare providers can prescribe the wrong medicine, the wrong dose, or the wrong mix of drugs. Combination drugs are another source of medication errors since the same drug could be taken in more than one formulation, leading to an overdose. More commonly, people may take too many doses if they aren’t tracking their medication use or misunderstand the instructions.

  • Medication accidents: Taking the wrong medicine or unwittingly overdosing on a drug is a common cause of overdose, particularly among children who have access to drugs. 

Risk factors for overdose

Because there are so many ways to overdose on a drug, there are multiple risk factors. The prime risk factors are:

  • Illicit drug use or prescription drug misuse: People who recreationally use illegal drugs or prescription drugs are at an increased risk of overdose for a variety of reasons. They may take too much on purpose, combine drugs with other drugs, use illicit drugs for self-harm, or take unknown substances. The quality of illicit substances is unpredictable and often leads to overdose. 

  • Mental illness: People with mental illnesses are at a higher risk of overdose due to substance abuse, self-harm, or medication errors. Some drugs used to treat mental illness, like antidepressants or anticonvulsants, may increase the risk of using drugs for suicide, especially in teens and younger adults.

  • Multiple prescriptions: The use of multiple prescription drugs, or polypharmacy, is a significant risk factor for drug interactions and overdose, particularly if prescription opioids are in the mix. The combination of certain drugs may lead to overdose, mismanaging doses, mixing up pills (especially if they have similar names), and there’s an increased risk of misunderstanding the dosing instructions.

  • Age: Advancing age can be a risk factor for overdose because of the risk of medication errors and making mistakes when taking drugs. On the other hand, children are also at high risk of drug overdose. This is why prescription drugs and over-the-counter medications usually come with the warning, “Keep out of reach of children.” Children’s medications are particularly risky if they are sweet or candy-like.

  • Drug sensitivity: Several medical conditions can cause drug levels to build up in the body. Most have to do with the body’s ability to clear the drug from the body. In those cases, people will need smaller doses than normal. Some drugs affect the way the body processes other drugs. Combining these drugs can lead to an overdose because one of the drugs is building up in the body.

  • Access to drugs: Easy access to drugs increases the risk that those drugs will be misused or overdosed, particularly by children or people intent on self-harm.

RELATED: Seniors’ guide to medication management

Is overdose serious? When to see a doctor

A drug overdose should be considered a medical emergency. The severity of the problem will depend on the drug and the amount taken, but healthcare professionals urge that immediate action be taken if an overdose is suspected. Call a poison helpline or go to an emergency room if the person can get there. If not, call 911 and follow their advice. 

In some cases, the poison helpline or 911 operator will determine that the situation is not serious or life-threatening. Follow their advice. Often, that advice will be to go to an emergency room.

Some drugs may take weeks or months of overdosing before causing problems. Emergency treatment may not be needed, but the symptoms should be evaluated by a healthcare professional.

How is overdose diagnosed?

An overdose can be easy or hard to diagnose. It all hinges on the first responders and healthcare professionals knowing what type of drug was taken, how much was taken, and when it was taken. If possible, bring the drug and its container with the prescription instructions to the emergency room. 

Diagnosis will primarily focus on the severity of the problem. Expect to answer questions about current medical conditions, allergies, and when the overdose was identified. Vital signs will be taken, a physical exam given, and a medical history taken. 

Is overdose hereditary?

Drug overdoses are due to decisions, actions, or mistakes that people or their healthcare providers make. 

Is overdose curable?

An overdose is treatable but not always curable. Some people will die of drug overdoses, even in an emergency room. Even if the overdose is successfully treated, complications can sometimes last for weeks or a lifetime. For instance, acetaminophen overdose is the number one reason why people in the U.S. get liver transplants.

Depending on the drug and the severity of the overdose, treatments can include:

  • Resuscitative treatment such as CPR

  • Eliminating the drug from the digestive system through activated charcoal, whole-bowel irrigation, or stomach emptying 

  • Antidotes such as naloxone for opioid overdose, acetylcysteine for acetaminophen overdose, or deferoxamine for iron poisoning

  • Reversal agents to counter the effects of the drug—for instance, sedatives are often given to counter the effects of a stimulant overdose

  • Drugs to stabilize symptoms

  • Dialysis to remove the drug from the bloodstream in more severe cases

RELATED: Opioid antagonists: uses, common brands, and safety info

How to prevent overdose

Drug overdoses are due to decisions or mistakes that people make, so overdoses are preventable. Here are some tips to ensure that drugs are used safely:

  • Make sure your healthcare providers are aware of all medications being taken, including over-the-counter drugs

  • Take all medications as instructed

  • Follow the directions on over-the-counter drugs

  • Never increase the dose of any prescription medication, over-the-counter drug, dietary supplement, or herbal remedy except under the advice of a healthcare professional

  • Do not take prescription medications that aren’t prescribed to you

  • Do not share medications with other people

  • Do not mix prescription drugs with alcohol or illicit drugs

  • Use an app or medication diary to keep track of doses to avoid unintended overdose, especially if multiple drugs are being taken each day

  • Keep track of the number of doses left in a bottle or container

  • When taking a prescription drug, read the drug information sheet and learn the specific signs of an overdose for that drug

  • Keep all medications, dietary supplements, and herbal remedies away from children, particularly “candy” medications or vitamins

  • Store prescription medications in the original bottle with the prescription label attached

  • Store medications in containers with child-resistant caps

  • Dispose of medications safely

  • Be careful not to take drugs with the same active ingredients, particularly over-the-counter combination medications such as cold or flu remedies

  • If using illicit drugs, avoid taking drugs when you are alone 

  • Do not mix illicit drugs with alcohol or other drugs

RELATED: What happens if you eat too many gummy vitamins?

Most importantly, get medical help

An overdose could be severe or not. The only way to know is to be evaluated by a healthcare professional. If an overdose is suspected, call a poison control center or 911 for advice. If there are symptoms of an overdose, get emergency medical care.

FAQs about overdose causes

How much fentanyl causes overdose?

Fentanyl is a powerful drug that is 50 to 100 times more powerful than morphine. 42% of street pills tested for fentanyl contain 2 mg—2,000 mcg—or more of fentanyl. That’s enough to kill someone. 

Can mixing prescription medications cause overdose symptoms?

Mixing prescription medications can cause overdose symptoms because some drugs can amplify the effects or side effects of each other. That can have additive effects, such as taking two sedatives. They can also have physiological effects. For instance, some drugs slow down or block the metabolism of other drugs. As a result, one of the drugs can build up in the body, resulting in an overdose.

What causes an accidental overdose?

Accidental overdoses are due to mistakes in managing doses, accidentally taking the wrong medicine, or when children or others get access to medications. Accidental overdose is more common r when taking multiple prescription drugs, so special care in managing doses is required. Illicit drugs are also a frequent source of accidental overdose. The quality of street drugs is unpredictable, leading to accidental overdose.

What’s next? Additional resources for people with overdose

Test and diagnostics

Treatments

Scientific studies and clinical trials

Medically reviewed by Anne Jacobson, MD, MPH
Board-Certified Family Physician

Anne Jacobson, MD, MPH, is a board-certified family physician, writer, editor, teacher, and consultant. She is a graduate of University of Wisconsin School of Medicine and Public Health, and trained at West Suburban Family Medicine in Oak Park, Illinois. She later completed a fellowship in community medicine at PCC Community Wellness and a master's in Public Health at the University of Illinois-Chicago. She lives with her family near Chicago.

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