Morphine and other opioid medications generally have these side effects:

• Sleepiness
  Some level of sleepiness or drowsiness is common when the medication is first started or the dosage increased. It usually lasts about two to three days.
   
• Fatigue 
   
• Nausea
  This may occur with the drowsiness. It too tends to subside after a few days, as the body gets used to the medication or increased dosage.
   
• Constipation
  Opioids generally slow the movement of the bowels. Therefore it’s important to take laxatives when taking opioids.
   
• Confusion or hallucinations
  Opioids may cause, or contribute to, confusion or hallucinations. If these are unpleasant and disturbing it’s important to notify the health care team who may suggest a change in pain medications.

Some medications, such as steroids, can affect a person's physical appearance. Morphine and other pain relievers do not. Any visible changes in someone taking morphine are usually related to the illness itself and its effects on the body. These may be from the general effects of the illness, or other effects, such as the impact of certain types of cancer tumors. Most cancers lead to decreased appetite and ability to eat, as well as ongoing weight loss. These eventually affect someone's physical appearance and capacity for activity.