[header] How to determine if you are too sick to work out [title] Forgo your workout if you have a fever. [step] Physical signs of fever include sweating and chills, body aches, headache, fatigue or weakness, low appetite, and your skin feeling warm to the touch. Take your temperature at home. 
Avoid exercise if you have a temperature over 100f (37.8c) or if you have any signs of fever. [substeps] A fever is your body's way of fighting infection, and is telling you that you need rest.