Fever
If you have a fever (usually between 101 and 104 degrees) or cold that sticks around longer than usual, it could be a sign of mono. “People should suspect mono when they have a prolonged cold-like illness or high fever and swollen glands. They should see their physician, who can confirm with a blood test,” says Adam Horblitt, MD, internal medicine physician at Westchester Medical Center in Valhalla, New York.