So if your illness is caused by a virus, it is usually better not to be taking an antibiotic. What may seem like the same thing may not be the same thing. Hundreds of viral and bacterial germs can cause what seems like the same illness. And even if you do have the same illness you had before, that doesn't mean the antibiotic helped, even if you got better while taking it. So when your doctor decides not to use an antibiotic, you may be avoiding other problems as well as additional costs.
Bacteria are more likely to become resistant to widely used antibiotics.
Eventually, a strain of bacteria may become completely resistant to a certain antibiotic. The best treatment for a viral illness may be plenty of non-caffeinated liquids, rest. Never take an antibiotic that has been prescribed for someone else. You could be allergic to it, and if you take it before being checked, it may interfere with a throat culture or other tests. Be sure to report to your provider any new problem, worsening of symptoms, or anything else that concerns you.