What Is the Worst Drug to Detox From? The Ones That Can Kill, the Ones That Only Feel Like They Will, and Why It Matters Which

There are two honest answers to this question, and they name different drugs. If “worst” means most dangerous, the answer is alcohol and benzodiazepines. Their withdrawal can cause seizures, and it can kill. If “worst” means hardest to sit through, many people would say opioids. That withdrawal is miserable, but it is rarely dangerous in itself. This page takes each drug in turn, with the medical sources for each claim. It ends with what makes any withdrawal worse, and what changes when it is done under care.

Alcohol withdrawal is dangerous because it can lead to seizures and delirium tremens. The National Library of Medicine says most people recover fully, but death is possible, especially if delirium tremens occurs.

Symptoms usually start within 8 hours of the last drink and peak at 24 to 72 hours. Most of the early symptoms are uncomfortable rather than dangerous: shakiness, sweating, nausea, anxiety and poor sleep. The danger comes later, and often after a person thinks the worst is over.

Seizures can come between 8 and 48 hours after the last drink. They can happen with no other warning signs. Delirium tremens, a state of severe confusion with fever and a racing heart, can start up to five days in. The clinical reference StatPearls puts its historical death rate as high as 20 percent. With prompt hospital treatment it is now about 1 percent. That gap is the whole case for medical detox. The hour-by-hour alcohol withdrawal timeline sets out each stage, and the seizures and DTs page covers the dangerous ones.

Source: Alcohol withdrawal, MedlinePlus Medical Encyclopedia, National Library of Medicine, reviewed January 1, 2025; Alcohol Withdrawal Syndrome, Canver, Newman and Gomez, StatPearls, updated February 14, 2024.

Opioid withdrawal itself is not usually dangerous. The National Library of Medicine calls its symptoms very uncomfortable but not life threatening. The danger is what can happen after it ends.

The symptoms come in two waves. The first brings anxiety, muscle aches, sweating, a runny nose, yawning and insomnia. The second brings cramps, diarrhea, goosebumps, nausea and vomiting. For heroin, they start within about 12 hours of the last dose. For methadone, they start within about 30 hours.

The risk after withdrawal is overdose. Detox takes away tolerance in a matter of days. A dose that was normal last week can now stop a person’s breathing. A 2003 study in the BMJ followed 137 people after inpatient opioid detox. Three died of overdose in the first four months. All three had completed detox and lost their tolerance. None of those who left early, still tolerant, died in that time. The authors called the finding counterintuitive, unless it comes from the loss of tolerance.

That is why the National Library of Medicine says people who go through opioid withdrawal again and again should be treated with long-term methadone or buprenorphine. With fentanyl now in most of the supply, the margin is thinner still. The heroin detox and opioid detox pages explain how that medication is started.

Source: Opiate and opioid withdrawal, MedlinePlus Medical Encyclopedia, National Library of Medicine, reviewed May 15, 2026; Loss of tolerance and overdose mortality after inpatient opiate detoxification: follow up study, Strang et al., BMJ, 2003.

Any withdrawal is worse after a past bad withdrawal, after mixing drugs, and after stopping all at once. A history of seizures or delirium in withdrawal is the strongest warning sign of all.

StatPearls is direct about the first point. A past withdrawal that included seizures or delirium makes the next one more likely to include them too. Each episode can make the next one worse. So a person who “got through it last time” may be at more risk this time, not less.

Mixing drugs adds risk in two ways. Alcohol and benzodiazepines act on the same system, so stopping both at once stacks the danger. The alcohol and benzo cross-tolerance page explains why. And withdrawal from one drug can hide withdrawal from another, so the dangerous one is missed.

Stopping all at once is the third factor, and the one a person can change. A taper or a medication schedule lowers the risk for alcohol and benzodiazepines. Medication eases opioid withdrawal enough that people finish it. Other drugs that need a careful taper include gabapentinoids such as Lyrica.

Source: Alcohol Withdrawal Syndrome, StatPearls, 2024.