Get emergency medical help if you have signs of an allergic reaction to morphine: hives; difficult breathing; swelling of your face, lips, tongue, or throat.
Opioid medicine can slow or stop your breathing, and death may occur. A person caring for you should seek emergency medical attention if you have slow breathing with long pauses, blue colored lips, or if you are hard to wake up.
Call your doctor at once if you have:
slow heart rate, sighing, weak or shallow breathing, breathing that stops;
chest pain, fast or pounding heartbeats;
extreme drowsiness, feeling like you might pass out;
serotonin syndrome - agitation, hallucinations, fever, fast heart rate, muscle stiffness, twitching, loss of coordination, nausea, diarrhea; or
low cortisol levels - nausea, vomiting, loss of appetite, dizziness, worsening tiredness or weakness.
Serious breathing problems may be more likely in older adults and people who are debilitated or have wasting syndrome or chronic breathing disorders.
Common morphine side effects may include:
drowsiness, dizziness, tiredness;
constipation, stomach pain, nausea, vomiting;
sweating; or
feelings of extreme happiness or sadness.
This is not a complete list of side effects and others may occur. Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.
 Morphine side effects (more detail)
