Opioid withdrawal and detox – what to expect

For short-acting opioids, symptoms typically begin within 12 to 24 hours of the last dose. For long-acting opioids such as methadone, onset is later, generally 12 to 48 hours or more.

Early symptoms most commonly include:

• yawning
• runny nose and watery eyes
• sweating
• muscle aches
• restlessness
• anxiety

These are uncomfortable but manageable. In a supervised detox setting, staff are on hand to monitor them from the start.

Symptoms typically reach their most intense point between 24 and 72 hours after the last dose. The Diagnostic and Statistical Manual of Mental Disorders (DSM-5), as cited in Shah and Huecker’s StatPearls research, identifies the full clinical picture at this stage. It involves nausea and vomiting, diarrhoea, stomach cramps, raised heart rate and blood pressure, dilated pupils, insomnia, goosebumps and chills, and profuse sweating. From a recovery expert’s point of view, medical supervision during this phase should be essential.

The psychological dimension of opioid withdrawal is often underestimated. The UK Government’s Opioid Substitution Treatment guide for keyworkers identifies depression, anxiety, restlessness, irritability, sleep disorders, and intense drug craving as self-reported withdrawal symptoms. These are distinct from the observable physical signs, and for many, these are harder to manage than physical symptoms. They don’t always resolve at the same rate. That’s why detox needs to transition into broader treatment, not end at physical stabilisation.

The World Health Organization’s Clinical Guidelines for Withdrawal Management set out the established clinical timeline. For short-acting opioids such as heroin, withdrawal begins within 8 to 24 hours of the last dose and typically lasts four to ten days. For long-acting opioids like methadone, onset is 12 to 48 hours, and the withdrawal period extends to 10 to 20 days. The first three days are the most intense for most people.

By days four to seven, physical symptoms generally begin to ease. Sleep, appetite, and energy start to return. The body is not fully recovered, but there is usually a clear shift away from the acute phase. Psychological symptoms can persist, and close support remains important throughout this period.

For most people, withdrawal doesn’t end when the acute phase resolves. The UK Guidelines on Clinical Management of Drug Misuse and Dependence (Department of Health and Social Care, 2017) describe a protracted withdrawal syndrome that can follow the acute phase. Low mood, poor sleep, and persistent craving can persist for weeks or months. 

This is post-acute withdrawal syndrome, or PAWS. If you’ve tried stopping before and found the difficulty lasted longer than you expected, this is likely why. This stage is a well-documented phase of recovery, and one that we’re here to support you through.

Partially activates opioid receptors to reduce withdrawal symptoms and cravings. Research indicates it’s started 12 to 18 hours after the last dose of a short-acting opioid, or 24 to 48 hours after a long-acting opioid such as methadone.

Methadone is a longer-acting opioid used to stabilise withdrawal and reduce the intensity of symptoms.

These are non-opioid medications that reduce the hyperactivity of the nervous system during withdrawal, easing anxiety, raised blood pressure, and muscle discomfort.

locks opioid receptors and is used to reduce the risk of relapse once detox is complete. It should not be started until withdrawal has fully resolved, as it can otherwise trigger acute withdrawal.

We don’t recommend unsupervised opioid withdrawal at home. The physical symptoms, including severe vomiting, diarrhoea, and the risk of dehydration, require medical monitoring. The psychological symptoms, including severe anxiety and depression, can become overwhelming without clinical support. Most importantly, if you relapse after a period without opioids, your tolerance will have dropped. The dose that felt normal before could now cause an overdose. Medically supervised residential detox addresses all of these risks.

Medical detox addresses physical dependence. It clears opioids from the body and manages withdrawal safely. But it doesn’t address what sits beneath the physical dependence: the behavioural patterns and psychological drivers that maintain it. Detox is the first step. Opioid addiction treatment is what follows, and it’s where the longer work of recovery happens.

The withdrawal experience is broadly similar regardless of whether the opioid was prescribed or illicit. The main clinical difference is timing. Short-acting opioids, including most prescription painkillers, oxycodone, and heroin, tend to produce faster-onset, shorter-duration withdrawal. Long-acting opioids like methadone produce slower-onset, longer-duration withdrawal. The clinical recommendation, medically supervised detox, is the same either way.

For short-acting opioids, symptoms typically begin within 8 to 24 hours of the last dose. For long-acting opioids such as methadone, onset is usually 12 to 48 hours or later. These timelines are established in the World Health Organization’s Clinical Guidelines for Withdrawal Management.

Yes. All three Castle Health clinics, Castle Craig, Smarmore Castle, and Beroendekliniken, accept patients from outside their home countries. If you are based outside the UK, Ireland, or Sweden and want to understand the admissions and travel process, please contact our team directly. We can talk through the options with you.