You have a fever that lasts more than a week. If you have a fever of 102 or higher, go in right away.
You can't hold down any food. If you have severe diarrhea for more than two days or even mild diarrhea lasting a week, it's probably time to visit the clinic. Constipation for more than two weeks or bloody diarrhea is another reason to go.
You're in pain, such as you'd have with a severe headache, backache, or stomachache. Get it checked out to (a) make sure it's nothing serious and (b) find some relief. Headaches with a fever, stiff neck, rash, mental confusion, or signs such as sensitivity to light or speaking problems are cause for concern.
You have red, swollen, and hot joints (such as hands, knees, or ankles), which could indicate a serious infection that needs urgent medical attention.
You've been "blue" for more than two weeks. Academic stress, homesickness, and social issues can lead to depression in students. Unexplained weight loss, difficulty falling asleep, or poor concentration may be signs of depression or other ailments that call for a check-up.