Westbrook Recovery

Opioid Withdrawal Timeline: The Clock, the Peak, and How It Is Actually Measured

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Withdrawal from a short-acting opioid like heroin or oxycodone usually starts about 12 hours after the last use, builds over the first day, peaks around days two to three, and resolves across roughly a week; methadone starts later, around 30 hours, and runs longer at both ends. That is the honest frame, and the hours are the least reliable part of it: clinicians do not run this on a calendar, they score it with an eleven-item instrument called COWS, repeated over time. We read that instrument from the primary documents, and it changes the useful question from "which day will be worst" to "how is this being measured". The part of this that is dangerous is mostly not the syndrome itself but what follows it, when tolerance is gone.

The short version

  1. Onset tracks the drug, not the calendar — about 12 hours for heroin and other short-acting opioids, about 30 for methadone; fentanyl has made any fixed hour unreliable
  2. The peak is days two to three — the acute phase resolves across roughly a week; sleep and mood take longer than the physical symptoms
  3. It is measured, not estimated — the COWS scale scores 11 signs into bands from mild to severe; we read it from the primary documents, and it is what times buprenorphine, not a clock
  4. The syndrome is miserable, not lethal — the direct dangers are aspiration and dehydration; the lethal risk is afterwards, when tolerance has fallen
  5. Detox alone is not treatment — the clinical expectation is a handoff to continuing care arranged before withdrawal ends, not after
  6. Naloxone belongs in the house — available without a prescription, and most important in the days right after withdrawal, not during it

Step by step

  1. Know which clock you are on

    The onset hour is set by how long the opioid acts: about 12 hours for heroin, oxycodone, hydrocodone and morphine, about 30 for methadone, and unpredictably for fentanyl. Everything else follows from which of those you are holding.

  2. Prepare the first three days

    Fluids you can keep down, electrolytes, a toilet within reach, loose clothing, and someone who knows. The peak days bring vomiting and diarrhoea, and the preparation that matters is hydration and an observer, not willpower.

  3. Measure instead of guessing

    If any clinician is involved, the COWS score is the number that matters: it tracks whether you are worsening or settling, and it is what decides when buprenorphine is safe to start. Ask for it by name if nobody mentions it.

  4. Arrange the other side before the week ends

    Detox is a doorway. Medication, a program, or both should be booked before the acute phase ends, because the highest-risk window for overdose is the days right after, when tolerance is gone and resolve is spent.

  5. Keep naloxone through the tail

    The weeks after withdrawal carry the overdose risk, not the withdrawal itself. Naloxone at home through that stretch is a precaution, like a fire extinguisher, not an expectation of failure.

Bar chart of withdrawal onset by opioid: about 12 hours after short-acting opioids like heroin, about 30 hours after methadone
The clock is set by how long the drug acts, not by the calendar. Fentanyl has made any fixed hour unreliable.
Curve of opioid withdrawal severity: onset, peak at days two to three, resolution across about a week, then the low tail
Worst at days two and three, resolving across the week, tail after. The hours are the least reliable part; the shape is reliable.
Three cards on where the danger actually sits in opioid withdrawal: the syndrome itself is not lethal, complications are aspiration and dehydration, the lethal risk is overdose afterwards
The part that kills is almost entirely on the other side of withdrawal, on a dose that used to be ordinary.
Diagram of the post-withdrawal window: tolerance low, resolve spent, overdose risk highest in the days after detox
Naloxone in the house through this stretch is a precaution, like a fire extinguisher, not an admission of failure.
Diagram of why fentanyl broke the timing rule: fat-soluble, accumulates in tissue, still leaving when the calendar says gone
The wait-a-fixed-number-of-hours instruction was written for a supply that no longer dominates.

The number your clinician is actually watching

Our analysis

Withdrawal is measured, not guessed. We read the instrument clinicians use, the COWS scale, from the primary documents on 15 October 2026, because it changes the useful question from which day will be worst to how is this being scored.

11
items scored on the COWS scale
mostly observed or measured by a clinician, not self-reported feelings
0-47
total score range
bands: 5-12 mild, 13-24 moderate, 25-36 moderately severe, above 36 severe
12
the induction threshold that matters
a COWS of 12+, not a count of hours, is what times a buprenorphine start per SAMHSA guidance
~2 min
per reading
which is why it is repeated: decisions follow the trend, not a snapshot
12h / 30h
onset after short-acting / methadone
the calendar answer, with fentanyl the reason it broke
2003
Wesson & Ling, J Psychoactive Drugs
bands set by clinical expertise, not statistics; we say so on the page

How we got this: we read the Clinical Opiate Withdrawal Scale from the primary documents on 15 October 2026: NIDA's published copy of the scale, the Wesson and Ling 2003 paper as reproduced in the validation literature, Tompkins and colleagues' 2009 concurrent validation, the NCBI Bookshelf item listing, and SAMHSA TIP 63 for the induction threshold. The item-by-item structure analysis is ours.

What these numbers cannot tell you: the bands are expert conventions, not statistically derived cutoffs, and the scale scores a moment in a clinical setting, not your living room; nothing here replaces an assessment by someone who can actually measure you.

The clock is set by which opioid it was

There is no single opioid withdrawal timeline, and pages that print one are averaging over drugs with very different clocks. The rule underneath is mechanical: withdrawal is the nervous system rebounding once the drug clears, so onset tracks clearance. Short-acting opioids start it about 12 hours after the last use; methadone, which leaves slowly, starts it around 30 hours. Everything else on this page hangs off that difference.

Short-acting: heroin, oxycodone, hydrocodone, morphine

Symptoms begin within about 12 hours, build through the first day, and hit their most intense stretch around days two and three. The acute phase resolves over roughly a week. This is the pattern most published timelines describe, and it is the one least likely to fit if fentanyl is involved, which the fentanyl section below is honest about.

Long-acting: methadone and the extended-release forms

Later onset, about 30 hours, and a drawn-out course rather than a compressed one: milder peak, longer tail. It is also why a methadone taper is managed over weeks. The same clearance logic runs both the withdrawal and the taper.

Why a calendar answer is the wrong tool

Onset varies with dose, duration, liver, other substances and formulation, so the hour printed on any page is a population midpoint. The clinical world solved this long ago by measuring the syndrome instead of reading the clock, which is what the next section is about.

How clinicians actually measure this

This is the part of the topic almost no ranking page prints, and it is the most useful thing on this one. Opioid withdrawal is not estimated by asking how bad it feels; it is scored on an instrument called the Clinical Opiate Withdrawal Scale, COWS, developed by Wesson and Ling in 2003 and now standard in emergency departments, detox units and opioid treatment programs. We read the scale from the primary documents rather than from pages about it.

  • under 5

    Reading
    no active withdrawal
    What it means in practice
    and the reason this band matters most: inducing buprenorphine here can precipitate it

  • 5 to 12

    Reading
    mild
    What it means in practice
    objective signs present; the upper end is where induction discussions start

  • 13 to 24

    Reading
    moderate
    What it means in practice
    the comfortable margin for a standard buprenorphine start

  • 25 to 36

    Reading
    moderately severe
    What it means in practice
    induction clearly appropriate; relief is typically rapid

  • over 36

    Reading
    severe
    What it means in practice
    advanced withdrawal; supervised setting
The COWS bands, from the scale itself (Wesson & Ling 2003; NIDA copy)

What the eleven items are

Resting pulse rate, sweating, restlessness, pupil size, bone or joint aches, runny nose or tearing, gastrointestinal upset, tremor, yawning, anxiety or irritability, and gooseflesh. Read that list and you notice what is on it: mostly things a clinician observes or measures, not things you report. That is deliberate, and it is why the scale resists both exaggeration and stoicism.

Why the score is repeated, not taken once

A single reading is a snapshot; the decision-making lives in the trend. The scale takes about two minutes, so it is run at intervals, and treatment responds to the direction of the number rather than to how anyone feels in the moment. This is also the instrument that decides when it is safe to start buprenorphine, which the timing section below leans on.

The honest caveat about the bands

The mild-to-severe bands were set by the authors' clinical expertise, not statistically derived, and a 2009 validation study noted the scale had never been systematically validated against a gold standard even as it became the de facto one. The bands are useful conventions with two decades of clinical mileage, not carved constants. We print them as what they are.

The first day

Early withdrawal is unmistakable once you have seen the list: agitation, anxiety, muscle aches, watering eyes, a runny nose, sweating, yawning, and sleep that will not come. People describe it as a severe flu arriving with restlessness attached. It is miserable and, on its own, not the phase that carries the complications.

What is actually happening

The principal site is the locus coeruleus at the base of the brain, dense with opioid receptors and running on noradrenaline. Opioids suppress it; remove them and it rebounds unopposed, which produces the sweating, racing pulse, restlessness and raised blood pressure. The flu feeling is a nervous system overshooting in the other direction.

What helps in the first day

Fluids before vomiting starts, a cool room, and someone present. None of it shortens anything; the first day is endured, not treated. What supervision adds is an observer who can tell miserable from deteriorating, which from the inside are indistinguishable.

The peak days

Days two and three carry the later group of symptoms: abdominal cramping, diarrhoea, dilated pupils, gooseflesh, nausea and vomiting. This is where fluid is lost, and it is the stretch the dangers live in: aspiration if vomiting is inhaled, and the dehydration and electrolyte disturbance that vomiting and diarrhoea together produce. It is also the stretch where the measured score matters most, because moderate on paper and deteriorating are different situations.

The tail: sleep and mood lag behind

The physical symptoms settling is not the end, and expecting it to be is how people conclude that stopping failed. Insomnia, low mood, low energy and blunted pleasure in ordinary things persist after the cramps and sweating have gone, on a slower clock than the acute syndrome. This is the documented course, not a sign of damage. The signs that the tail is turning into a slide are on our relapse warning signs page.

Fentanyl and the timing problem

Most published timelines were written for heroin and prescription opioids, and the supply changed underneath them. Fentanyl is highly fat-soluble and accumulates in tissue with repeated use, so it can still be leaving the body when the calendar says it should be gone. The practical consequence: the old instruction, wait a fixed number of hours then start buprenorphine, became unreliable, because starting while fentanyl is still on the receptors can precipitate abrupt, severe withdrawal.

What replaced the clock

Measurement. The induction threshold that SAMHSA's guidance works from is a COWS score of 12 or higher, moderate withdrawal actually observed, rather than a number of hours elapsed. Low-dose induction protocols, titrating buprenorphine gradually without requiring full withdrawal first, exist for the same reason and are implemented in exactly the settings where fentanyl users actually are. If a provider tells you the wait-and-start hours rule is the only option, that is worth a second opinion.

What this does not mean

It does not mean fentanyl withdrawal is a different or worse syndrome, and "fentanyl withdrawal is unbearable" is a widely repeated claim that discourages people from starting at all. What changed is the timing and its predictability, and the answer to both is measuring instead of reading a calendar. The narrower finding has a solution attached to it.

Is opioid withdrawal dangerous?

The honest answer has three parts, and most pages print only one of them. People ask whether opioid withdrawal is life threatening because the other famous withdrawals can be: this one is not typically life threatening to a healthy adult, and there is no equivalent of the alcohol withdrawal seizure. The complications are real: aspiration from vomiting, and dehydration with electrolyte disturbance, both more serious in anyone already unwell, elderly, pregnant, or alone. And the part that actually kills people is afterwards: tolerance falls during withdrawal, and most opioid overdose deaths occur in people who have just come through it, on doses that used to be ordinary.

When to escalate, not endure

Persistent vomiting that prevents keeping fluids down, signs of dehydration, chest pain, confusion, a climbing fever, or withdrawal alongside pregnancy or significant illness: those move this from a home event to a supervised one. The same is true when nobody is around to notice deterioration.

What helps: the medication picture honestly

There are two separate things medication can do, and conflating them is why people conclude nothing works. One is easing the syndrome while it runs; the other is not making you go through it at all.

For the symptoms

Lofexidine, approved by the FDA in 2018 specifically for managing opioid withdrawal, acts on the same noradrenergic overactivity that produces most of the physical symptoms. Around it sit the symptomatic measures clinicians list: loperamide for diarrhoea, anti-nausea medication, ibuprofen for the aches, clonidine for the autonomic storm. None treats the disorder; they make a bad week less bad, which is worth having and is not the same as being treated.

For the disorder

Buprenorphine or methadone treat the condition rather than the syndrome, and federal guidance is direct that people who go through withdrawal over and over should be on long-term maintenance rather than repeatedly detoxing. If this is not your first attempt, that sentence is about you. The withdrawal-angle detail of how buprenorphine is started safely is on our Suboxone withdrawal timeline page; the bigger difference between managing withdrawal and treating the disorder is on detox vs rehab.

Detox kits and rapid offers

Nothing purchasable compresses a week of neuroadaptation into days. Detox drinks and flush kits are marketed at drug tests rather than withdrawal and do not reliably serve either. What a program can honestly compress is risk and misery, not time.

At home versus supervised

Home withdrawal happens and is sometimes reasonable: quitting cold turkey is how most people actually stop a short-acting opioid, since there is nothing to taper with. What makes it defensible is an assessment first, no other substances, no significant illness, and someone present, not the absence of a bed. Supervision buys the two things a mattress cannot: an observer for the complications, and the handoff arranged before the week ends, which is where detoxes go to die.

Comparison of the old clock rule against the measurement rule: a fixed number of hours versus a COWS score of 12 or higher observed
SAMHSA guidance times buprenorphine by the measured score, not the clock. That is the answer the fentanyl era needed.
Two columns separating medications that ease withdrawal symptoms from those that treat the disorder: lofexidine and symptomatic care against buprenorphine and methadone maintenance
One column makes a bad week less bad; the other treats the condition. Confusing them is why people conclude nothing works.
The COWS scale structure: eleven clinician-scored items from resting pulse to gooseflesh, total 0 to 47, bands mild through severe
Withdrawal is measured, not guessed. We read the scale from the primary documents, and the bands are expert conventions, printed as such.
Escalation checklist for opioid withdrawal: persistent vomiting, dehydration signs, chest pain, confusion, climbing fever, pregnancy or illness alongside, nobody present
Any of these moves this from a home event to a supervised one. None of them is a toughness test.

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.

  1. Detox19.5% of facilitiesmedical withdrawal management, 3–7 daysDetox vs rehab
  2. Residential21.4% of facilitieslive on site, 24-hour staffingInpatient vs outpatient
  3. PHP20–30 structured hours a week, sleep at homePHP vs IOP
  4. IOP9–19 hours a week, usually compatible with workPHP vs IOP
  5. 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.”

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.

Warning cards about detox drinks, flush kits and rapid-detox offers marketed against withdrawal searches
Nothing purchasable compresses a week of neuroadaptation into days. What a program compresses is risk and misery, not time.
Diagram of the handoff: detox ends into arranged continuing care, medication or a program booked before the week ends
Detox is a doorway, not a room. Leaving with nothing booked is how a completed detox turns into nothing.
Checklist for a defensible home withdrawal: short-acting opioid, no other substances, no significant illness, someone present, assessment first
Home can be reasonable. What makes it defensible is the assessment, not the absence of a bed.
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?

For short-acting opioids like heroin or oxycodone: onset about 12 hours after the last use, peak around days two to three, resolution across roughly a week. Methadone starts later, about 30 hours, and runs longer at both ends. Sleep and mood settle slower than the body. Fentanyl has made any fixed hour unreliable, which is why clinicians score severity instead of counting hours.

When does opioid withdrawal start?

About 12 hours after the last use of a short-acting opioid, and around 30 hours after methadone. The first signs are yawning, a runny nose, watering eyes, sweating, restlessness and muscle aches, building through the first day.

Is opioid withdrawal dangerous?

The syndrome itself is miserable but not usually lethal to a healthy adult. The real dangers are the complications, aspiration and dehydration, and above all what follows: tolerance falls during withdrawal, and most opioid overdose deaths occur in people who have just detoxed. Supervision matters less for the week than for the handoff after it.

What is a COWS score?

The Clinical Opiate Withdrawal Scale: an 11-item clinician-administered score from 0 to 47 that turns withdrawal into a number tracked over time. Bands run 5-12 mild, 13-24 moderate, 25-36 moderately severe, over 36 severe. It is also the instrument that times a safe buprenorphine start: 12 or higher, not a fixed wait.

What is precipitated withdrawal?

Withdrawal triggered by a medication rather than by the absence of the drug: buprenorphine started while full agonists still occupy receptors, or naltrexone taken too early. It arrives abruptly and severely. It is why induction is timed by a measured score, and why fentanyl, which lingers in tissue, broke the old wait-fixed-hours rule.

Can I detox from opioids at home?

People do, and for a short-acting opioid with no other substances, no significant illness and someone present it can be reasonable. Persistent vomiting, dehydration signs, chest pain, confusion or fever move it to supervised care, as does being alone. The case for supervision is the complications watch and the arranged handoff, not willpower.

Does detox treat the addiction?

No. Withdrawal management treats the body through the syndrome; it does nothing for why use continued, and detox alone is associated with rapid return to use. Federal guidance is direct that repeated withdrawal is the indication for long-term buprenorphine or methadone maintenance instead.

Should naloxone be in the house?

Yes, especially in the days and weeks after withdrawal, when tolerance is gone and a former dose can kill. Naloxone reverses opioid overdose and is available without a prescription at US pharmacies. It is a precaution, not an expectation.

Sources

Compare levels of care

Check what your plan covers

How this page was made

Who wrote it:
the Westbrook Recovery 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:
8 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:
. 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.

Related on this site

More guides

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.