The short answer to your question is no, you should not take antibiotics that have not been prescribed by a physician or other health care professional for a specific reason. I should also mention that it is likely that the antibiotic you have is Augmentin (which contains amoxicillin) as 875 mg is not a usual dose of amoxicillin alone but rather the dose often used in the combination medication Augmentin. The majority of the time that someone develops a sore throat
it is due to other types of infections other than strep throat. That is not to say that at a sore throat should be ignored, it is just that it should be treated as strep throat only when that is what is suspected by a doctor
. I suggest that you schedule an appointment with your primary care physician
. He or she will examine your throat first and then using the throat exam combined with your age and other factors will determine if a rapid strep test needs to be sent. If it does, and comes back positive, then you should be treated with penicillin. If it comes back negative, then the sore throat is likely viral and you should be treated with medications that reduce the pain while you are recovering. Good luck.