You shouldn't take more than 1 pill when taking Unisom. 3 pills would most likely be considered an overdose. If you think you have taken too much, seek emergency medical attention. Overdose symptoms may include dizziness, drowsiness, feeling restless or nervous, dry mouth, warmth or tingly feeling, nausea, vomiting, diarrhea, stomach pain, loss of appetite, increased sweating, seizure (convulsions), or coma.