Withdrawal symptoms can start anywhere from a few hours to several days after your last dose, depending on the substance. The key factor is how quickly the drug leaves your body. Substances that wear off fast, like alcohol or short-acting opioids, trigger withdrawal sooner. Longer-acting substances like methadone can take days before symptoms appear.
Why Half-Life Determines When Withdrawal Starts
Every substance has a “half-life,” which is the time it takes for the amount in your bloodstream to drop by half. After one half-life, you’re at 50% of your last dose. After two, you’re at 25%. After five half-lives, the drug is essentially gone from your body. Withdrawal symptoms typically begin well before that point, often once blood levels drop below the threshold your body has adapted to.
This is why short-acting substances cause withdrawal faster. Your body adjusts to a certain level of the drug, and when that level plummets quickly, the nervous system rebounds. Drugs with short half-lives reach that tipping point in hours rather than days. Drugs with long half-lives taper themselves more gradually, which delays the onset of symptoms and often makes them less intense.
Alcohol: 6 to 24 Hours
Alcohol withdrawal is among the fastest to appear. Mild symptoms like headache, anxiety, and trouble sleeping typically show up within 6 to 12 hours of your last drink. Within 24 hours, some people experience hallucinations. Seizure risk is highest between 24 and 48 hours. The most dangerous phase, delirium tremens, can develop 48 to 72 hours after the last drink, though it only occurs in a subset of heavy, long-term drinkers.
The speed of alcohol withdrawal catches many people off guard. Because alcohol is metabolized relatively quickly, the body begins reacting within the same day you stop drinking.
Opioids: 6 Hours to 4 Days
Opioid withdrawal timing splits cleanly by the type of opioid. Short-acting opioids like heroin, oxycodone, and hydrocodone typically produce withdrawal symptoms within 6 to 12 hours after the last dose. You’ll feel muscle aches, restlessness, anxiety, and sweating early on, with symptoms peaking around 36 to 72 hours.
Long-acting opioids tell a different story. Methadone, for instance, has a much longer half-life, so withdrawal may not start for 72 to 96 hours after the last dose. The tradeoff is that methadone withdrawal, while slower to arrive, tends to last longer overall.
Benzodiazepines: Hours to Days
Benzodiazepines follow the same half-life logic, but the range is wide because the class includes drugs with vastly different durations of action. Short-acting benzodiazepines like alprazolam (Xanax) can trigger withdrawal symptoms faster than long-acting ones like diazepam (Valium). As a general rule, symptoms begin within 24 hours, though they may appear sooner with short-acting formulations.
Benzodiazepine withdrawal is notable for how long it can stretch. While early symptoms might start within a day, the full withdrawal process can last weeks or even months, particularly for people who used high doses over a long period. This is one reason these drugs are typically tapered gradually rather than stopped abruptly.
Nicotine and Caffeine: Within Hours
Nicotine withdrawal is fast. Cravings can start within one to two hours of your last cigarette or tobacco use. Irritability, difficulty concentrating, and increased appetite follow within the first day. Symptoms generally peak in the first few days and then gradually ease over two to four weeks, though cravings can persist longer.
Caffeine withdrawal follows a similar rapid timeline. If you’re a regular coffee drinker, skipping your usual cup can produce a headache within 12 to 24 hours. The classic caffeine withdrawal headache, along with fatigue and difficulty concentrating, peaks around one to two days and resolves within about a week for most people.
What Makes Withdrawal Start Sooner or Later
The substance itself is the biggest factor, but it’s not the only one. How long you’ve been using matters: someone who drank heavily for a decade will generally experience withdrawal differently than someone who binged for a few weeks. Higher doses over longer periods give your body more time to adapt, which means the rebound when you stop is more pronounced.
Your individual metabolism plays a role too. People who metabolize substances faster will clear the drug sooner and may feel withdrawal earlier. Age, liver function, body composition, and overall health all influence this. If you use multiple substances, withdrawal timelines can overlap and complicate the picture.
Mental health also shapes the experience. Anxiety, depression, and sleep problems can amplify withdrawal symptoms or make them harder to distinguish from the withdrawal itself. Some people develop post-acute withdrawal syndrome, where subtler symptoms like mood swings, sleep disruption, and difficulty concentrating persist for months after the acute phase ends. The duration of this extended phase depends on the substance used, the length of use, and individual health factors.
Quick Reference by Substance
- Alcohol: 6 to 24 hours after last drink
- Short-acting opioids (heroin, oxycodone): 6 to 12 hours after last dose
- Long-acting opioids (methadone): 72 to 96 hours after last dose
- Short-acting benzodiazepines (Xanax): within 24 hours, often sooner
- Long-acting benzodiazepines (Valium): 1 to 4 days after last dose
- Nicotine: 1 to 2 hours after last use
- Caffeine: 12 to 24 hours after last dose