Get emergency medical help if you have any of these signs of an allergic reaction: hives; difficulty breathing; swelling of your face, lips, tongue, or throat. Stop using olanzapine and call your doctor at once if you have any of these serious side effects:
very stiff (rigid) muscles, high fever, tremors, sweating, confusion, fast or uneven heartbeats, slow heart rate, feeling like you might pass out;
twitching or uncontrollable movements of your eyes, lips, tongue, face, arms, or legs;
trouble speaking or swallowing;
dry mouth, thirst, feeling very hot (with or without sweating), urinating less than usual or not at all;
high blood sugar (increased thirst, loss of appetite, fruity breath odor, increased urination, drowsiness, dry skin, nausea, and vomiting);
sudden numbness or weakness, confusion, or problems with vision, speech, or balance;
fever, chills, body aches, flu symptoms, sores in your mouth and throat;
swelling in your hands or feet;
changes in personality, unusual thoughts or behavior, hallucinations, or thoughts about hurting yourself; or
upper stomach pain, itching, loss of appetite, dark urine, clay-colored stools, jaundice (yellowing of the skin or eyes).
Less serious side effects may include:
weight gain (more likely in teenagers), increased appetite;
headache, dizziness, drowsiness, feeling tired or restless;
stomach pain, constipation, loss of bladder control;
back pain, pain in your arms or legs;
numbness or tingly feeling;
breast swelling or discharge (in women or men); or
missed menstrual periods.
This is not a complete list of side effects and others may occur. Call your doctor for medical advice about side effects.