You took the pill your doctor gave you. Now you feel sleepy. But it is the middle of the day. You had a good night's sleep. Why do you feel sleepy?
Your doctor gives you drugs to help cure your sickness. But sometimes drugs can make you feel bad in other ways. This is called a side effect.
Feeling sleepy might be a side effect of the drug you took. In fact, it is one of the most common side effects of drugs. Sometimes there will be a warning on the label, "may cause drowsiness."
Another common side effect is an upset stomach. Many kinds of medicines might make you feel sick to your stomach. They might cause diarrhea or vomiting.