It really depends on what is wrong with me, sometimes I work through it with a full workout - cardio and weights. Sometimes I hit the treadmill for 30 minutes of good walking and call it a day. Then sometimes I stay home, use my DVDs and hand weights and then sometimes I just pull the covers over my head. The point is to go but not lose your form. I can't workout if I am congested and if I take something my head gets wonky.
Remember some meds tell you not to operate heavy machinery.