Opioid and fentanyl withdrawal: what to expect, and a safer way through

Help right now: if someone won't wake up, is breathing slowly or not at all, or has blue or gray lips, call 911 and give naloxone (Narcan) if you have it. In a mental health or substance use crisis, call or text 988, any time. SAMHSA's National Helpline, 1-800-662-4357, is free, confidential and open 24/7 for treatment referrals.

The short version

1. Withdrawal is miserable but usually not life-threatening. MedlinePlus says the symptoms are very uncomfortable but not life-threatening. Vomiting and diarrhea can still cause dehydration, so get medical help.
2. The biggest danger is after withdrawal. MedlinePlus says most opioid overdose deaths happen in people who have just detoxed, because their tolerance is gone.
3. Medication works better than detox alone. The National Institute on Drug Abuse (NIDA) says medication should be the first line of treatment for opioid addiction, and that people on methadone or buprenorphine are less likely to die or overdose.
4. Get naloxone. It reverses opioid overdoses and is sold without a prescription.

Symptoms and timeline

MedlinePlus lists these symptoms. Early on:

• Anxiety, agitation, trouble sleeping
• Muscle aches
• Runny nose, watery eyes, yawning, sweating

Later:

• Stomach cramps, nausea, vomiting, diarrhea
• Goosebumps and dilated (big) pupils

Opioid	When withdrawal starts	How long it usually lasts
Heroin and other short-acting opioids	Usually within 12 hours of the last use (MedlinePlus); a WHO guideline gives 8 to 24 hours	About 4 to 10 days (WHO)
Methadone (long-acting)	Usually within 30 hours of the last dose (MedlinePlus); WHO gives 12 to 48 hours	About 10 to 20 days (WHO)
Fentanyl	Varies; see below	Still being studied

Those are rough ranges. Your dose, how long you've used, other drugs and your health all change how it goes. Trouble sleeping, low mood and cravings can last for weeks after the worst is over, and that's when many people go back to using.

Fentanyl is different

Most street opioids today are fentanyl or contain it. A 2025 research review in the Annual Review of Clinical Psychology says there's real debate about whether fentanyl withdrawal follows a different pattern, and one study it cites found withdrawal in people using fentanyl kept getting worse over the first 3 days.

Fentanyl also changes how buprenorphine is started. Some people who start buprenorphine too soon after fentanyl get sudden, intense withdrawal ("precipitated withdrawal"). Clinicians now use different ways to start, including very low starting doses or a quick high dose. The same review says there's no head-to-head research yet on which is best. Tell your prescriber you've been using fentanyl so they can plan your start. Our guide on how to start Suboxone explains what to expect.

Why detox alone is risky

When you stop opioids for even a few days, your body loses its tolerance. If you use again, especially the amount you used before, it can stop your breathing. NIDA says that after quitting, people can easily overdose because their bodies are no longer used to the drug. MedlinePlus says most opioid overdose deaths happen in people who have just detoxed.

Detox also rarely ends the addiction by itself. NIDA says detox is not the same as treatment, and that detox alone, without treatment afterward, generally leads back to drug use. With fentanyl in the drug supply, a return to use after detox is especially dangerous.

This isn't a reason to give up. It's a reason to plan for more than detox: start medication, or at least leave detox with a treatment appointment and naloxone in hand.

Medication: the path with the best evidence

Medication for opioid use disorder (MOUD, sometimes called MAT) uses FDA-approved medicines, usually alongside counseling. NIDA says people who get methadone or buprenorphine are less likely to die or overdose than people who don't get treatment, and both help people stay in treatment.

Medicine	How it works	Where you get it
Buprenorphine (Suboxone, Sublocade and others)	A partial opioid that eases withdrawal and cravings, with weaker effects than full opioids. You usually start once you're in early withdrawal (SAMHSA says at least 12 to 24 hours after your last opioid; fentanyl can change this).	Any clinician with a standard DEA registration can prescribe it if state law allows, since the special "X-waiver" was removed at the end of 2022. Also at opioid treatment programs.
Methadone	A long-acting full opioid, taken daily, that reduces craving and withdrawal and blunts the effects of other opioids.	For opioid use disorder, only at a SAMHSA-certified opioid treatment program (a "methadone clinic"). After a period of stability, some doses can be taken at home.
Naltrexone (Vivitrol, monthly shot)	Not an opioid. It blocks opioids from working and reduces cravings.	Any licensed prescriber. You have to be off opioids first: SAMHSA says at least 7 days for short-acting opioids and 10 to 14 days for long-acting ones.

Some people stay on medication for months, others for years. SAMHSA says the length of buprenorphine treatment is tailored to each person and can be indefinite, and that methadone treatment should last at least 12 months. Stopping should be planned with your prescriber, not done suddenly.

Comparing the three? See medication options for opioid addiction. Ready to start buprenorphine? See how to start Suboxone.

If you still want detox

Some people want to come off opioids completely. That's your choice to make with a clinician, and medical detox is much safer than doing it alone. If you go this way:

• Ask about medicine for withdrawal. Buprenorphine or methadone can be used to ease withdrawal. NIDA notes that lofexidine (Lucemyra) treats withdrawal symptoms but isn't a long-term treatment.
• Ask about naltrexone before you leave. Once you've been off opioids long enough, a monthly naltrexone shot can protect against a return to use. SAMHSA warns that after stopping naltrexone, tolerance is low, so even a smaller dose than before can be deadly.
• Leave with naloxone and a next appointment, with a date and time.
• Know you can change your mind. If cravings are strong after detox, starting buprenorphine or methadone is not a failure. It's treatment.

Naloxone: carry it

Naloxone (Narcan and other brands) reverses an opioid overdose. SAMHSA says the FDA approved naloxone nasal spray for sale without a prescription in March 2023. The CDC says you can buy it at pharmacies and many other stores, and community naloxone programs often give it out for free. It works on fentanyl, though the CDC says stronger opioids may need more than one dose.

Keep it where people can find it, tell family and friends where it is, and replace it when it expires. Naloxone only works on opioids, but SAMHSA says it still reverses an opioid overdose when opioids were mixed with other drugs. If you think it could be an opioid overdose, give it and call 911.

If you're pregnant

Don't stop opioids suddenly on your own. SAMHSA says withdrawal during pregnancy may raise the risk of miscarriage or premature birth, and that buprenorphine and methadone are the treatments of choice for pregnant and breastfeeding women with opioid use disorder. Tell any program you call that you're pregnant: programs paid by the federal substance use block grant have to give pregnant women priority for admission.

Where to get help

Cima Find Care lists programs in Texas, Louisiana, Oklahoma, Arkansas, Missouri, Kansas and Mississippi, including detox programs and programs that offer medication.

• Texas medication programs: Houston, Dallas, San Antonio and Austin. Detox: Houston, Dallas, San Antonio and Austin.
• Louisiana: New Orleans programs with medication
• Oklahoma: Oklahoma City and Tulsa
• Arkansas: Little Rock
• Missouri: St. Louis and Kansas City
• Kansas: Wichita
• Mississippi: Jackson

Wondering how to pay? See what detox costs and who pays. Not sure where to start? Answer four quick questions. SAMHSA's FindTreatment.gov lists licensed programs nationwide, including opioid treatment programs. For the levels of care after detox, see IOP vs PHP vs weekly therapy, and for insurance basics, does insurance cover rehab?

Questions people ask

Can opioid withdrawal kill you?

Withdrawal itself is rarely life-threatening, but vomiting and diarrhea can cause dangerous dehydration, and someone who vomits while very drowsy can breathe it into their lungs. The bigger risk is overdose afterward, because tolerance drops fast. Get medical help either way.

Isn't buprenorphine or methadone just trading one drug for another?

No. Taken as prescribed, they treat a medical condition. NIDA says people on them are less likely to die or overdose and more likely to stay in treatment. They're taken at steady doses, under a clinician's care, alongside counseling.

How soon can I start buprenorphine after fentanyl?

It depends, and fentanyl can make starting harder. SAMHSA's general guidance is to be in early withdrawal, at least 12 to 24 hours after your last opioid, but prescribers often adjust the plan for fentanyl, for example with very small starting doses. Tell them exactly what you've been using.

Where do I get naloxone?

At most pharmacies without a prescription, and free from many community programs and health departments. Ask the treatment program you call, too.

Do I need detox before starting medication?

Not for buprenorphine or methadone: you can start without a separate detox. Naltrexone is different, because you have to be off opioids for 7 to 14 days first, so it often starts after detox.

Will my insurance pay for this?

Medicaid, Medicare and private insurance can all pay for detox and for medication for opioid use disorder, but what's covered, and what needs approval first, varies by plan. See what detox costs and who pays.

Sources

• MedlinePlus (National Library of Medicine): Opiate and opioid withdrawal, reviewed May 2026
• National Institute on Drug Abuse: Medications to treat opioid use disorder, March 2025
• National Institute on Drug Abuse: Treatment and recovery
• SAMHSA: Buprenorphine, Methadone and Naltrexone
• SAMHSA: Waiver elimination (MAT Act)
• SAMHSA: Opioid overdose reversal medications
• CDC: What to do if you think someone is overdosing and Lifesaving naloxone
• World Health Organization: Clinical guidelines for withdrawal management and treatment of drug dependence in closed settings (2009), opioid withdrawal timing
• Martinez S, Ellis JD, Bergeria CL, Huhn AS, Dunn KE. Treating opioid use disorder and opioid withdrawal in the context of fentanyl. Annual Review of Clinical Psychology, 2025
• 45 CFR 96.131: Treatment services for pregnant women (block grant admission priority)
• SAMHSA: National Helpline and FindTreatment.gov