What are the signs of serious opioid withdrawal?

Here’s a direct, clinical list of the signs of serious opioid withdrawal — the kind that indicates a person is in moderate to severe withdrawal and may need medical support or stabilization.

Serious (Moderate–Severe) Opioid Withdrawal Signs

Autonomic (high-risk) symptoms

• Rapid pulse (racing heart)

• High blood pressure

• Heavy sweating

• Chills and gooseflesh

• Profuse yawning

• Severe anxiety or panic

• Intense restlessness / inability to sit still

Gastrointestinal symptoms (severe)

• Uncontrolled vomiting

• Explosive diarrhea

• Severe abdominal cramping

• Inability to keep fluids in → dehydration risk

Neurological / physical symptoms

• Severe muscle and bone pain

• Severe leg kicking / jerking (“restless legs”)

• Marked tremors

• Dilated pupils (very large)

• Deep chills, shaking, sweating cycles

Psychological symptoms

• Severe agitation

• Intense craving

• Irritability or aggression

• Intrusive thoughts or despair

• Insomnia for 24–48 hours

• Feeling unable to cope or function

Red-flag symptoms (medical attention recommended)

These are not typical “just uncomfortable” withdrawal — they are dangerous:

• Dehydration (no urine, dry mouth, dizziness when standing)

• Chest pain or heart palpitations

• Vomiting blood or black stool

• Uncontrolled shaking

• Confusion, disorientation

• Fainting / near-fainting

Important Context

• Serious withdrawal is almost never life-threatening by itself, but it can become dangerous through dehydration, electrolyte imbalance, or complications like aspiration.

• People withdrawing from methadone, fentanyl, or long-acting opioids often experience more prolonged and intense symptoms.

• The worst stage is usually 24–72 hours after last use (depending on the opioid).