Opioid Withdrawal Timeline: What Happens, and When

Last updated August 28, 2026

Withdrawal usually begins about 12 hours after the last use of a short-acting opioid such as heroin or oxycodone, and around 30 hours after methadone. Early symptoms are agitation, anxiety, muscle aches, watering eyes, a running nose, sweating, yawning and sleeplessness; the later ones are abdominal cramping, diarrhoea, dilated pupils, gooseflesh, nausea and vomiting. Two things this timeline does not tell you matter more than the hours. Fentanyl behaves differently enough that standard guidance can mislead. And the dangerous part is not the withdrawal itself — it is what happens afterwards, because tolerance falls and most opioid overdose deaths occur in people who have just come through it.

The short version

Onset: about 12 hours after heroin, 30 after methadone — the longer the opioid acts, the later withdrawal starts and the longer it runs
Not usually life-threatening in itself — but two federal sources word this differently, and the reason is worth understanding
The overdose risk is afterwards — NIH states that most opioid overdose deaths occur in people who have just detoxed
Fentanyl breaks the standard playbook — it raised the risk of precipitated withdrawal enough that low-dose induction protocols exist because of it

Bar chart of when opioid withdrawal begins: about 30 hours after methadone, about 12 hours after heroin and other short-acting opioids — The same syndrome, arriving more than a day apart. The longer the opioid acts, the later withdrawal starts and the longer it runs.

Five-step diagram of withdrawal stages: early symptoms, later symptoms, peak on days two and three, settling over a week, then a longer tail of sleep and mood — Knowing which stage you are in is more useful than counting hours — the second group is the one that carries the complications.

Table resolving whether opioid withdrawal is dangerous: the syndrome rarely kills directly, causes no seizures, but aspiration and dehydration are real and the lethal risk comes afterwards — MedlinePlus says not life threatening; StatPearls calls it life-threatening. Both are correct about different things, and the difference is mechanical.

Three figures on post-withdrawal risk: deaths occur after rather than during, tolerance falls during withdrawal, naloxone reverses overdose — The lethal risk of opioid withdrawal sits almost entirely on the other side of it — which is why detox without a plan for afterwards is what clinicians worry about.

Five-step diagram of why fentanyl changed opioid withdrawal management: fat-soluble, accumulates in tissue, leaves slowly, old timing rule unreliable, low-dose induction — Most timelines online were written for heroin. The supply changed underneath them, and the induction advice changed with it.

Where withdrawal can actually be managed

Our analysis

The timeline is the same everywhere; what differs is whether there is anywhere to go through it with supervision, and whether the medication that prevents having to go through it at all is within reach. Nobody publishes those proportions, so we counted them.

19.5%: of facilities run medical detox; 1,996 of 10,233 — among the scarcer services, and the one this page is about
59.2%: offer buprenorphine; the alternative to going through withdrawal rather than managing it
13.7%: offer methadone; restricted to certified programmes, which is why access differs so sharply

How we got this: we pulled the full public listing from SAMHSA’s FindTreatment.gov on August 25, 2026, removed duplicate entries by name, street and ZIP, and counted how many of the 10,233 remaining facilities report each service. SAMHSA publishes the directory; it does not publish these proportions — see how the count is made. Repeat the pull and you will get the same numbers, give or take facilities that opened or closed since.

What these numbers cannot tell you: they are self-reported by facilities, they describe availability rather than quality, and a national proportion says nothing about what is open near you this week. Use them to know what to ask for — not to decide where to go.

The timeline, by which opioid was used

There is no single opioid withdrawal timeline, and pages that publish one are averaging over drugs that behave very differently. What sets the clock is how long the opioid acts: the shorter-acting it is, the sooner withdrawal starts and the sooner it finishes. MedlinePlus puts the start at within 12 hours of the last heroin use and within 30 hours of the last methadone exposure — the same syndrome, arriving more than a day apart.

Short-acting opioids: heroin, oxycodone, hydrocodone, morphine

Symptoms typically begin within about 12 hours, build over the first day, and are at their most intense during roughly the second and third days. The acute phase is generally described as resolving over something like a week, with sleep and mood taking longer to settle than the physical symptoms. This is the pattern most published timelines describe, and it is the one least likely to apply if fentanyl is involved.

Long-acting opioids: methadone in particular

Onset is later — within about 30 hours of the last dose — and the whole course is drawn out rather than compressed. That is a direct consequence of how slowly the drug leaves the system, and it is also why a methadone taper is managed over weeks rather than days. The trade-off is real in both directions: a later start, a milder peak, and a longer tail.

Why the difference exists at all

Withdrawal is not the drug leaving; it is the nervous system re-adjusting once it does. The principal site is the locus coeruleus at the base of the brain, whose neurons are noradrenergic and densely supplied with opioid receptors. Opioids suppress activity there; remove them and that activity rebounds unopposed, which is what produces the sweating, the racing pulse, the restlessness and the raised blood pressure. The speed of that rebound tracks how fast the drug clears.

What the symptoms actually are, early and late

Clinical sources separate these into two groups, and the order is fairly reliable even when the timing is not. Knowing which stage you are looking at is more useful than counting hours, because the second group is the one that carries the complications.

Early

Agitation, anxiety, muscle aches, watering eyes, a running nose, sweating, yawning and insomnia. Unpleasant and unmistakable, but not the phase that causes harm. People frequently describe this stage as feeling like the onset of severe flu with an added restlessness that makes staying still difficult.

Late

Abdominal cramping, diarrhoea, dilated pupils, gooseflesh, nausea and vomiting. This is where fluid is lost and where the genuine risks sit. The full clinical picture also includes autonomic overactivity — fast breathing, fast pulse, sweating, raised blood pressure and raised temperature — which is what a clinician is watching when they take observations rather than asking how you feel.

How severity is actually measured

Not by how bad it feels. Clinicians use the Clinical Opiate Withdrawal Scale, COWS, which scores eleven signs and symptoms to produce a number that drives decisions. That matters practically: it is repeated at intervals, so treatment responds to a trend rather than to an impression, and it is the same instrument used to judge whether it is yet safe to start buprenorphine.

Fentanyl changes the picture

Most timelines circulating online were written for heroin and prescription opioids, and the drug supply has changed underneath them. This is the single most consequential update on this page, and it is recent enough that a great deal of published material has not caught up.

Why the standard advice can mislead

Fentanyl is highly fat-soluble and accumulates in body tissue with repeated use, which means it can still be leaving the system when the calendar says it should be gone. The practical consequence is that the familiar instruction — wait a set number of hours, then start buprenorphine — became unreliable. Research published in 2026 states the problem plainly: fentanyl’s penetration into the unregulated drug supply has complicated treatment, particularly by increasing the risk of buprenorphine-precipitated opioid withdrawal, and traditional induction methods can be intolerable for people using fentanyl.

What clinicians started doing instead

Low-dose induction, sometimes described as micro-dosing: buprenorphine is titrated gradually without requiring a period of withdrawal first, rather than waiting for symptoms and then starting at a normal dose. It exists specifically to avoid precipitating the withdrawal that the old approach risks, and it is being implemented in exactly the settings where people actually are — including syringe service programmes. If a provider tells you the wait-and-start approach is the only option, that is worth a second opinion.

What this does not mean

It does not mean fentanyl withdrawal is a different syndrome, and it does not mean the symptoms are worse in kind. What changes is the timing, its predictability, and therefore how medication should be started. The distinction matters because “fentanyl withdrawal is unbearable” is a widely repeated claim that discourages people from starting treatment at all, when the actual finding is narrower and has a solution attached to it.

Is opioid withdrawal dangerous? Two federal sources word this differently

This is the most searched question about the subject, and the honest answer starts by acknowledging a real disagreement. MedlinePlus, published by the National Library of Medicine, states that the symptoms are very uncomfortable but are not life threatening, and elsewhere that withdrawal from opiates is painful but usually not life threatening. StatPearls, hosted on the NIH Bookshelf, opens by describing opioid withdrawal syndrome as a life-threatening condition. Both are federal clinical sources. Neither is wrong, and the resolution is mechanical rather than a matter of opinion.

What is true about the syndrome itself

Unlike alcohol and benzodiazepine withdrawal, opioid withdrawal does not typically kill a healthy adult directly. There is no equivalent of the withdrawal seizure or the delirium that makes those two medically dangerous in their own right. That is the sense in which the reassuring wording is correct, and it is why opioid withdrawal is often managed outside a hospital when nothing else complicates it.

What is true about the complications

The dangers are real and they are specific. Vomiting can lead to breathing stomach contents into the lungs — aspiration — which can cause a lung infection. Vomiting and diarrhoea together cause dehydration and disturbances of body chemistry and minerals. Both are listed by MedlinePlus as possible complications, and both are considerably more serious in someone who is already unwell, elderly, pregnant, or without anyone around to notice deterioration. That is the sense in which the stronger wording is correct.

And the part that actually kills people

MedlinePlus states it without hedging: the biggest complication is returning to drug use, and most opiate overdose deaths occur in people who have just detoxed. Withdrawal reduces tolerance, so someone who has just been through it can overdose on a much smaller dose than they used to take. The lethal risk of opioid withdrawal is almost entirely on the other side of it — which is exactly why detox on its own, without a plan for what follows, is the arrangement clinicians worry about most.

When to get medical help rather than wait it out

Persistent vomiting that prevents keeping fluids down, signs of dehydration, chest pain, confusion, a fever that keeps climbing, or any withdrawal happening alongside pregnancy or a significant existing illness. Also worth escalating: withdrawal in someone who cannot be observed. MedlinePlus advises contacting a provider if you are using or withdrawing from opiates at all — not because the syndrome is usually dangerous, but because the alternative to supervision is doing this without anyone measuring whether it is going wrong.

What actually helps, and what the medication is for

There are two separate things a clinician can do here, and confusing them is why people conclude that nothing works. One is easing symptoms while withdrawal runs its course. The other is not putting you through withdrawal at all.

The non-opioid approved specifically for this

In May 2018 the FDA approved lofexidine hydrochloride, the first non-opioid medication for managing opioid withdrawal syndrome. It is an alpha-2 adrenergic agonist, which is to say it acts on the same noradrenergic overactivity that produces most of the physical symptoms. It treats the syndrome; it does not treat the underlying disorder, and it does nothing for craving.

Symptomatic treatment

Clinical guidance describes loperamide for diarrhoea, promethazine for nausea and vomiting, and ibuprofen for muscle pain, with clonidine used to reduce the blood pressure and autonomic symptoms. None of these is a treatment for opioid use disorder. They make a bad week less bad, which is worth having and is not the same thing as being treated.

Or not going through withdrawal at all

The alternative that most pages bury: starting buprenorphine or methadone means the withdrawal is treated rather than endured. Both are treatments for the disorder rather than for the syndrome, and both continue afterwards. MedlinePlus is direct about who this applies to — people who go through withdrawal over and over should be treated with long-term methadone or buprenorphine maintenance. If this is not your first attempt, that sentence is about you, and it is the most actionable line on this page — and the comparison of how those two differ on access and retention evidence is where to go next.

The timing rule, and why fentanyl bends it

Buprenorphine can precipitate withdrawal in someone who is dependent but not yet in withdrawal, which is why the conventional instruction is to start it 12 to 18 hours after the last short-acting opioid and 24 to 48 hours after a long-acting one such as methadone. That rule was written for a supply that no longer dominates, which is what the low-dose induction protocols above respond to. Naltrexone carries the same hazard in a stronger form: taken while opioids are still in the system it brings on sudden, severe withdrawal.

After the acute phase

The physical symptoms settling is not the end of the process, and expecting it to be is a common source of the conclusion that treatment failed.

Sleep, mood and energy lag behind

Insomnia, low mood, low energy and difficulty feeling pleasure in ordinary things frequently persist after the cramps and sweating have gone. This is well recognised clinically and it is not a sign that something has gone wrong; it is the nervous system continuing to re-adjust on a slower timescale than the acute syndrome runs on.

Why this period carries the risk it does

It combines the lowest tolerance with the point at which the initial resolve has worn off and nothing structural has yet replaced it. That combination is why the days and weeks after withdrawal are when overdose deaths cluster, and why having naloxone in the house through this period is a concrete precaution rather than an admission of expected failure.

What is supposed to happen next

Detox is the doorway, not the room. The clinical expectation is that withdrawal management hands over to something continuing — medication, a level of care, or both — arranged before it finishes rather than after. Leaving with nothing booked is the single most common way a completed detox turns into nothing.

How this page differs from choosing a medication

A note on scope, because the two questions overlap in search results and answer different things. This page describes what withdrawal does over time and what can be done about the syndrome itself. Which long-term medication to be on — buprenorphine, methadone or naltrexone, and what decides between them — is a separate decision made with a prescriber, and it turns on access, retention evidence and circumstances rather than on withdrawal timing. If you are past the question of what the next few days look like and onto what happens for the next year, that is the comparison you want rather than this page.

What this page cannot tell you

How your own withdrawal will go. The timelines here are population patterns, and individual courses vary with the opioid, the dose, how long it was used, other substances involved and other conditions present. Nothing here is a plan for managing withdrawal without medical input, and no doctor has reviewed this page. What it is for is knowing what to expect, what genuinely warrants concern, and which questions to put to someone who can actually assess you.

Five-step diagram of medication timing: 12 to 18 hours after short-acting opioids, 24 to 48 after methadone, why starting early precipitates withdrawal, and what changes with fentanyl — The interval exists to avoid precipitating the withdrawal it is meant to relieve — and it is exactly the rule fentanyl made unreliable.

Table separating medications that ease withdrawal from those that treat the disorder: lofexidine, clonidine and symptomatic drugs against buprenorphine, methadone and naltrexone — Confusing these two columns is why people conclude that nothing works. Only one of them continues after the week is over.

Checklist of how clinicians measure opioid withdrawal: the eleven-item COWS scale, repeated at intervals, driving medication decisions, based on observations — Severity is scored rather than estimated, which is the practical difference between managed and unmanaged withdrawal.

Warning checklist of when to seek help during opioid withdrawal: persistent vomiting, dehydration signs, chest pain or confusion, pregnancy or illness, nobody present — None of these is an expected part of withdrawal. Supervision is the variable that makes the difference, not the discomfort.

Where this sits in the system of care

Addiction treatment is organised into levels of care, and clinicians choose between them using the ASAM criteria — six dimensions covering withdrawal risk, medical and psychiatric conditions, readiness, relapse risk and, decisively, the environment you return to. Facilities are licensed by the state and many hold additional accreditation from bodies such as the Joint Commission or CARF; that status is worth confirming for any specific programme. Percentages below are our count of how many facilities in the federal directory report offering each level of care.

Detox19.5% of facilitiesmedical withdrawal management, 3–7 daysDetox vs rehab
Residential21.4% of facilitieslive on site, 24-hour staffingInpatient vs outpatient
PHP20–30 structured hours a week, sleep at homePHP vs IOP
IOP9–19 hours a week, usually compatible with workPHP vs IOP
Standard outpatient85.4% of facilities1–8 hours a week, the maintenance levelMutual aid options

“Remaining in treatment for an adequate period of time is critical.”
— National Institute on Drug Abuse, Principles of Effective Treatment

Programmes for specific groups

Facilities also report dedicated programming, and the coverage is wider than most people expect — worth asking about before assuming a programme will not fit. From our count: 42.7% run programmes for adolescents, 39.2% for veterans, 38% for pregnant and postpartum women, and 25% provide services in Spanish. Medication for opioid use disorder is available at 59.2% (buprenorphine) and 13.7% (methadone).

Cost and coverage vary by level: residential care is the tier insurers scrutinise most and almost always requires prior authorisation before admission. See what your plan covers and how to pay without insurance. Family involvement is a standard part of most programmes, and aftercare planning — step-down to a lower level, sober living, relapse prevention — should be discussed before admission, not at discharge. If a mental health condition is also present, ask specifically whether the programme is staffed for co-occurring disorders: 69.5% of facilities in the directory report treating them, but that is a self-reported field worth confirming.

Checklist correcting four beliefs about opioid withdrawal: getting through it alone, detox as treatment, fentanyl as a different syndrome, and danger passing when symptoms end — Each of these is common enough to change a decision, and each is wrong in a way that costs something.

Five-step diagram of what follows withdrawal: managed, nothing treated yet, tolerance now low, next level arranged, and repeated withdrawals indicating maintenance — The last step is the one MedlinePlus states outright: repeated withdrawal is an indication for long-term maintenance rather than another detox.

Bar chart of availability: 85.4% of US facilities offer outpatient treatment, 59.2% buprenorphine, 21.4% residential, 19.5% medical detox, 13.7% methadone — Medical detox is among the scarcest services on this list, and the medication that avoids needing it is among the most available.

Bar chart of medication for opioid use disorder availability: buprenorphine at 59.2% of facilities, methadone at 13.7%, certified opioid treatment programmes at 12.8% — The four-to-one gap between buprenorphine and methadone availability is a regulatory fact, not a clinical judgement about which works better.

Bar chart of how many US treatment facilities offer each level of care: outpatient 85.4%, residential 21.4%, medical detox 19.5%, hospital inpatient 5.9% — Outpatient care is nearly universal; residential and detox are the scarce tiers. That scarcity is part of why they cost what they do and why waits exist.

Diagram of the step-down pathway through addiction treatment: detox, residential, partial hospitalisation, intensive outpatient, then outpatient and aftercare — Nobody needs every step. The ladder exists so that support can be reduced as stability improves, not so that everyone starts at the top.

Checklist of the six ASAM assessment dimensions: withdrawal risk, medical conditions, emotional and behavioural conditions, readiness to change, relapse potential, and recovery environment — This is the framework US programmes and insurers actually use. The sixth dimension — what home is like — is the one families most often underestimate.

Checklist of six questions to ask a treatment facility about network status, prior authorisation, all-in cost, medication availability, aftercare and accreditation — How plainly a programme answers these is itself information about how it operates.

Bar chart of payment types accepted by US addiction treatment facilities: cash 91.6%, private insurance 80.7%, Medicaid 83.4%, Medicare 55.2%, state-financed 54.5%, military 49.6%, sliding scale 40.0%, payment assistance 22.5% — Accepting your insurer is not the same as your plan covering the level of care you need. The two questions have to be asked separately.

Three figures: 69.5% of facilities treat co-occurring disorders, 59.8% offer trauma-informed care, 19.5% run medical detox — Co-occurring capability is self-reported. Ask what it means concretely — which clinicians are on staff, and whether psychiatric medication can be prescribed and reviewed on site.

Table showing when to call 911, 988 or the SAMHSA National Helpline for overdose, immediate danger, suicidal thoughts, severe distress and treatment questions — All three are free and staffed around the clock. 988 is the Suicide & Crisis Lifeline; the SAMHSA National Helpline is 1-800-662-4357.

Common questions

How long does opioid withdrawal last in total?

For short-acting opioids the acute phase is commonly described as running about a week, with the worst of it around the second and third days. Methadone runs longer at both ends because it leaves the body slowly. Sleep, mood and energy usually take longer to settle than the physical symptoms, and that tail is normal rather than a sign that something has gone wrong.

Can opioid withdrawal kill you?

The syndrome itself does not typically kill a healthy adult, unlike alcohol or benzodiazepine withdrawal. The deaths associated with it come from complications — aspiration and dehydration — and, far more often, from what follows: MedlinePlus states that most opiate overdose deaths occur in people who have just detoxed, because tolerance falls during withdrawal.

Why does everyone say fentanyl withdrawal is worse?

What actually changed is the timing rather than the severity. Fentanyl accumulates in tissue, so it can still be leaving the system when standard guidance says it should be gone — which raised the risk of precipitated withdrawal when buprenorphine is started on the old schedule. Low-dose induction protocols exist specifically to work around that.

What is a COWS score?

The Clinical Opiate Withdrawal Scale, an eleven-item assessment a clinician uses to score withdrawal severity. It is repeated at intervals so that treatment follows a measured trend rather than an impression, and it is also used to judge whether it is yet safe to start buprenorphine.

Can I go through opioid withdrawal at home?

It is done, and whether it is reasonable depends on what else is true — other conditions, pregnancy, other substances, and whether anyone is around to notice deterioration. What makes it defensible is an assessment first rather than the absence of insurance. If persistent vomiting, dehydration, chest pain, confusion or a climbing fever appear, that is a reason to seek help rather than to push through.

Does going through withdrawal treat the addiction?

No. Withdrawal management addresses the body; it does not address why use continued, and detox alone is associated with rapid return to use. MedlinePlus is explicit that people who go through withdrawal repeatedly should be treated with long-term methadone or buprenorphine maintenance instead.

Should I keep naloxone during withdrawal?

Yes, and particularly afterwards. Tolerance falls during withdrawal, so a dose that was once ordinary carries a far higher risk in the days that follow. Naloxone reverses opioid overdose and is available without a prescription at US pharmacies.

What is precipitated withdrawal?

Withdrawal brought on deliberately or accidentally by a medication rather than by the absence of opioids. Buprenorphine can cause it in someone dependent but not yet in withdrawal, which is why timing matters; naltrexone causes it more severely if opioids are still present, which is why it requires a clear interval first.

Sources

Compare levels of care

Check what your plan covers

How this page was made

Who wrote it:: the Treatment Compass editorial team — researchers and writers, not clinicians. No doctor has reviewed this page, and we do not claim otherwise. What that means in practice: we report what public clinical sources say and show you where to read them, rather than offering a clinical opinion of our own.
Checked against:: 10 primary sources listed above — federal agency material and published clinical criteria. Where a figure varies by state, plan or facility, we say so instead of publishing a number that looks authoritative and is not.
Original analysis:: the facility proportions on this page are our own count of SAMHSA’s public directory. The full method is documented — including what we count, what we deliberately do not publish, and an error the approach caught. You can repeat the pull and check the numbers.
Last reviewed:: August 28, 2026. This date changes when the content is actually re-checked, not automatically on every visit.
What this page is not:: a medical recommendation, a diagnosis, or a referral. Decisions about levels of care and medication belong with a clinician who knows your history. We do not operate facilities, take placement fees, or receive payment for sending anyone anywhere.

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Paying for Rehab Without InsuranceState-funded programmes, sliding-scale fees, federal block grants and payment plans. What each option actually is, who qualifies, and how to reach it.
Rehab Rules: What You Can and Cannot Do in TreatmentWhat treatment facilities restrict and why: phones, visitors, relationships, leaving early. Rules vary by level of care, so here is what to ask first.

Weighing levels of care? See PHP vs IOP and what your insurance covers.

This page is information, not medical or legal advice. Laws on commitment and treatment differ by state. If you are in crisis, call or text 988 in the US, or reach the SAMHSA National Helpline at 1-800-662-4357 — free, confidential, 24/7.