Last reviewed: July 2026

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SAMHSA National Helpline — 1-800-662-HELP (4357) Free, confidential, 24/7, in English and Spanish. They will find treatment near you. FindTreatment.gov — search for treatment yourself. 988 — Suicide & Crisis Lifeline, call or text. In an emergency, call 911.

What You Need to Know

Withdrawal is not treatment. Getting through detox and stopping there is the single most dangerous thing you can do. Your tolerance drops fast — and a dose that was normal two weeks ago can kill you now. Most overdose deaths after treatment happen to people who detoxed and got nothing else.
The medication is the treatment. Buprenorphine and methadone cut death rates by more than half. They are not “swapping one addiction for another.” They are the reason people survive.
What you’re withdrawing from is probably not heroin. Fentanyl has largely replaced it. That changes the timeline, the severity, and how safely you can start buprenorphine.
Opioid withdrawal is rarely fatal by itself — but it can be. Severe vomiting and diarrhea can cause dangerous dehydration. And if you also use benzodiazepines or alcohol, those withdrawals can kill you.
Carry naloxone. It’s available over the counter now. It’s for you and for anyone around you.

What Opioid Withdrawal Is

Withdrawal — “dope sickness” — is what happens when the body has adapted to a constant opioid supply and that supply stops or drops sharply.

It is a physical event, not a failure of will. With repeated use, the body adjusts its own chemistry to compensate for the drug. Remove the drug and that compensation is suddenly unopposed, and it produces every symptom below. This is why willpower is largely irrelevant to how bad withdrawal feels, and why “just tough it out” is such useless advice.

Withdrawal can happen to anyone who’s been using regularly — including people who never intended to. Patients on long-term prescribed opioids for pain go into withdrawal when their prescription stops abruptly, and some are hospitalized for something unrelated and start withdrawing without anyone realising what’s happening. (See also prescription drug addiction and hydrocodone addiction.)

Symptoms

Early (roughly the first 24 hours):

Anxiety, agitation, restlessness
Muscle aches
Runny nose, watering eyes, yawning
Sweating
Insomnia

Later (peaking around 24–72 hours):

Abdominal cramping
Diarrhea
Nausea and vomiting
Dilated pupils
Goosebumps
Rapid heart rate, high blood pressure
Intense drug craving

Timeline (short-acting opioids like heroin): begins 8–24 hours after last use, peaks at 1–3 days, and the acute phase eases over about a week.

With fentanyl, throw that timeline out. Onset can be delayed and the whole thing can drag on considerably longer, because fentanyl accumulates in body tissue and leaves slowly. Many people find fentanyl withdrawal worse and longer than heroin withdrawal.

Sleep problems, low mood, anxiety, and cravings can persist for weeks or months after the physical symptoms resolve. This is normal, it is not a sign you’re broken, and it’s a major reason people return to use — which is precisely why medication matters.

The Part That Kills People

Read this even if you skip everything else.

Withdrawal drops your tolerance fast. After even a few days without opioids, the amount your body can survive falls dramatically. Take the dose you were taking before, and it can stop your breathing.

The highest-risk moments for fatal overdose are:

Right after detox or leaving a treatment programme
Right after release from jail or prison
Right after a hospital stay

All of these are periods of forced abstinence followed by a return to use at the old dose. This is why detox-only programmes have such a poor safety record, and why the goal should never be simply “get through withdrawal.”

If you use again after any break, use far less than you used to. Never use alone. Have naloxone in the room.

Fentanyl and Xylazine Changed the Rules

Fentanyl

The unregulated supply is now dominated by fentanyl. If you buy “heroin,” assume it’s fentanyl unless you’ve tested it.

For withdrawal, the practical consequences are:

It stays in your system far longer than heroin. In people who use regularly, fentanyl is detectable in urine for around a week after last use, because it accumulates in fat and muscle and releases slowly.
That extends the window for precipitated withdrawal when starting buprenorphine (below).
Withdrawal may start later and last longer than the classic heroin timeline.

Xylazine (“tranq”)

Xylazine — a veterinary sedative — is now widely mixed into the fentanyl supply. The federal government designated fentanyl adulterated with xylazine an emerging drug threat in 2023. What matters for you:

It is not an opioid. Opioid medications don’t treat xylazine withdrawal, and naloxone doesn’t reverse its sedation. (Still give naloxone — there’s almost always fentanyl in there too, and naloxone will reverse that.)
Xylazine withdrawal is its own thing — agitated, distinctive, and there is no approved medication for it. It needs to be managed in a treatment setting.
It causes severe skin wounds that can become dangerous. Get them looked at; don’t wait.

If you’re going into withdrawal and something feels different from what you’ve experienced before, xylazine may be why. Tell whoever is treating you.

Is Withdrawal Dangerous?

Opioid withdrawal on its own is usually not fatal in an otherwise healthy adult. But “usually not fatal” is doing some work in that sentence, and there are real exceptions:

Situation	Why it matters
Severe vomiting and diarrhea	Can cause dangerous dehydration and electrolyte loss. This has killed people, particularly in custody settings where it went unmanaged.
You also use benzodiazepines or alcohol	Those withdrawals genuinely can be fatal — seizures, delirium tremens. This is not something to attempt alone. See Xanax withdrawal and physical alcohol addiction.
You’re pregnant	Do not attempt withdrawal. Opioid withdrawal in pregnancy carries risk to the pregnancy. The standard of care is methadone or buprenorphine, continued through pregnancy. See a clinician immediately.
Heart, lung, or kidney disease	The physiological stress of withdrawal is not trivial on top of these.

The bigger danger, though, isn’t the withdrawal itself. It’s what comes after. See the section above.

Treatment: What Actually Works

The medications (MOUD)

Three medications are approved for opioid use disorder, and two of them save lives at scale:

Buprenorphine (Subutex; Suboxone when combined with naloxone) — a partial opioid agonist. It relieves withdrawal, blocks cravings, and reduces all-cause mortality by more than 50%. It can be prescribed in ordinary medical settings, including many emergency departments.

Methadone — a full agonist, dispensed through licensed opioid treatment programmes. Comparable mortality benefit. More structure, daily dosing, but for some people it works when buprenorphine doesn’t.

Naltrexone (Vivitrol, extended-release) — an opioid blocker. It can only be started after you’re fully through withdrawal, which is the practical catch: many people never make it to that point.

These are treatment, not a substitute addiction. You will hear otherwise — from family, sometimes from clinicians who should know better. The evidence is not ambiguous. Someone on buprenorphine or methadone is far more likely to be alive in five years than someone who detoxed and white-knuckled it.

Precipitated withdrawal — the thing to understand before you start buprenorphine

Buprenorphine binds very tightly to opioid receptors and knocks other opioids off them. If you take it while there’s still a lot of fentanyl in your system, it can slam you into sudden, severe withdrawal — far worse than what you were already feeling. This is precipitated withdrawal, and it is the reason a lot of people refuse buprenorphine or walk out of treatment.

What you need to know:

It’s a minority outcome, not an inevitability. One hospital study found around 12% of patients using fentanyl experienced it during a standard or high-dose buprenorphine start.
Timing is the main lever. Taking buprenorphine within 24 hours of fentanyl use raised the odds of severe withdrawal roughly fivefold in one large multi-site study. Clinicians use a scoring tool (the COWS scale) to judge when you’re withdrawn enough to start safely.
There are workarounds. “Low-dose initiation” protocols start with very small buprenorphine doses while you’re still using, and build up. Ask about them.
If it happens, it’s treatable — usually with more buprenorphine, under supervision.

Tell your prescriber you’re using fentanyl. Not heroin, not “opioids” — fentanyl, and how recently. This single piece of honesty changes how they start you and is the difference between a manageable start and a brutal one.

Comfort medications

Clonidine and lofexidine ease physical symptoms — sweating, cramping, agitation. Others target specific symptoms: anti-nausea drugs, anti-diarrheals, sleep aids.

Be clear about what these are. They make withdrawal more bearable. They do not treat opioid use disorder, and they do not reduce your risk of dying. If a programme offers you only comfort meds and a discharge date, it is offering you the dangerous half of the treatment. See making the most of your medications.

⚠️ “Rapid Detox” Under Anesthesia — Don’t

Some clinics still market ultra-rapid detox: you’re put under general anesthesia and given large doses of opioid-blocking drugs, on the theory that this compresses withdrawal into a few unconscious hours.

The evidence does not support it, and people have died.

It has not been shown to reduce the actual time spent in withdrawal.
There have been multiple deaths, particularly when performed outside a hospital.
Withdrawal causes vomiting. Vomiting under anesthesia carries a serious risk of aspiration.
It leaves you with zero tolerance and no ongoing medication — the exact profile of a fatal overdose, as described above.

Most addiction specialists consider the risks to clearly outweigh the unproven benefits. It is expensive, it is dangerous, and it is sold hardest to families who are desperate. Spend the money on buprenorphine or methadone and a year of real treatment instead.

Naloxone: Carry It

Naloxone (Narcan) reverses opioid overdose. It’s available over the counter in the U.S. — no prescription needed.

Get it. Keep it where you are. Tell someone where it is.
It won’t hurt anyone who isn’t overdosing.
Give it even if xylazine might be involved — there’s almost certainly fentanyl too, and naloxone reverses that.
Always call 911. Naloxone can wear off before the opioid does. Most states have Good Samaritan laws protecting people who call for help.
Never use alone. If you’re going to use, have someone with you, or use a phone-based overdose hotline.

Getting Help

SAMHSA National Helpline: 1-800-662-HELP (4357) — free, confidential, 24/7. They don’t ask for insurance and they don’t call the police.
FindTreatment.gov
Emergency departments increasingly start buprenorphine on the spot. You can walk in and ask. See before you go to the ER, read this.
Your primary care doctor may be able to prescribe buprenorphine directly — many can now. Ask. Getting the most from your doctor may help with that conversation, and do you know your medical rights covers what you’re entitled to.
Cost: if the medication is the barrier, see how to save on prescription drugs. Medicaid covers MOUD in every state.

Depression and anxiety travel with opioid use disorder in both directions, and treating them is part of treating this. See help for the mind and choosing a mental health provider.

If you’re supporting someone else: you cannot detox them at home safely, and pushing them toward a detox-only programme may put them at greater risk than doing nothing. Push for medication instead. Helping loved ones through depression covers some of the same ground on how to be useful without burning out.

The Bottom Line

Getting through withdrawal is the beginning of treatment, not the end of it. The people who survive this are, overwhelmingly, the people who come out of withdrawal onto buprenorphine or methadone and stay on it.

If you take one thing from this page: detox alone is the most dangerous option, not the purest one.

Global Statistics

Heroin & Opioid Withdrawal: Symptoms, Timeline, and What Actually Keeps You Alive

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